CHAPTER                                                                              6           Neoplasia                ...
116        Concise Pathology for Exam Preparation                Q. What is desmoplasia?           Ans. Hyperplasia of fib...
Neoplasia           117                Q. Differentiate between a hamartoma and a neoplasm.           Ans. Differences bet...
118           Concise Pathology for Exam Preparation               Abnormal nuclear morphology:               – Abundant a...
Neoplasia             119                Q. Differentiate between metaplasia and dysplasia.           Ans. Differences bet...
120         Concise Pathology for Exam Preparation            Features                       Benign                       ...
Neoplasia      121               (c) Lymphatic spread tends to follow natural routes of lymphatic drainage and is         ...
122        Concise Pathology for Exam Preparation               – Carriers of a mutant form of RB suppressor gene, have a ...
Neoplasia       123            3. Environmental and cultural factors               (a) Cigarette smoking: Oral cancers, ca...
124           Concise Pathology for Exam Preparation                        (viii)   Long-standing ulcerative colitis.    ...
Neoplasia              125                                Q. Differentiate between anti-oncogenes and proto-oncogenes.    ...
126        Concise Pathology for Exam Preparation                Q. Write briefly on role of cyclins, CDK (cyclin-dependen...
Neoplasia      127               Avoiding cellular ageing: Involving telomeres and telomerase in cancer.               Con...
128        Concise Pathology for Exam Preparation                      (ii) Growth factor receptors:                      ...
Neoplasia        129                            and regulates the cell cycle by transcriptional activation and its levels ...
130         Concise Pathology for Exam Preparation                             – Role in promoting apoptosis              ...
Neoplasia       131                  (j) Cadherins                        (i) Cadherins are a family of transmembrane prot...
132        Concise Pathology for Exam Preparation                                              Invasion of ECM            ...
Neoplasia    133                        – Acylating agents                             1-acetyl imidazole.                ...
134         Concise Pathology for Exam Preparation           Mechanism: Indirect acting carcinogens require metabolic acti...
Neoplasia     135                 (b) Epstein–Barr virus (EBV): Implicated in the pathogenesis of:                       (...
136        Concise Pathology for Exam Preparation                         – Insulin-like growth factor II and receptors fo...
Neoplasia        137                Q. Differentiate between DNA and RNA oncogenic viruses.           Ans. Differences bet...
138        Concise Pathology for Exam Preparation                 (d) Gastric and bronchial carcinoid syndromes are produc...
Neoplasia    139            3. Histochemistry/cytochemistry (special stains): These are diagnostic tools for              ...
140        Concise Pathology for Exam Preparation               (c) Shape of nucleus, features of nuclear membrane, and nu...
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Concise pathology for exam preparation 2e by geetika khanna exclusive preview. To Order Call at +91 8527622422


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This book presents an exhaustive and thorough
exposition of fundamentals of pathology in
question and answer format. Chapters are
organized logically for better understanding
of the topics. The book is based on Robbins and
Cotran's Pathologic Basis of Disease.

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Concise pathology for exam preparation 2e by geetika khanna exclusive preview. To Order Call at +91 8527622422

  1. 1. CHAPTER 6 Neoplasia Q. Define neoplasia. Ans. Neoplasia (new growth) is excessive and unregulated proliferation that eventu- ally becomes autonomous (independent of physiologic growth stimuli). Q. Define oncology. Ans. It is the study of the tumors and neoplasms (oncos in Greek means tumor). Q. Define cancer. Ans. It is the common term for the malignant tumors (derived from the Latin word crab, indicating adherence to any part it seizes upon obstinately like a crab). Q. What is clonality? Ans. A tumor is said to be clonal when the entire population of cells within a tumor arises from a single cell that has incurred genetic change. Q. What are the two components of all neoplasms? Ans. Two components of all neoplasms are: 1. Proliferating neoplastic cells called parenchyma Cross talk between 2. Supporting stroma of connective tissue and parenchyma and stroma blood vessels Directly influences the growth of the tumorChapter-06.indd 115 7/25/2011 1:37:58 PM
  2. 2. 116 Concise Pathology for Exam Preparation Q. What is desmoplasia? Ans. Hyperplasia of fibroblasts and formation of abundant collagenous stroma as a reaction to infiltration by cancer, is labeled desmoplasia. Q. Define and classify benign tumors? Ans. Benign tumors are neoplasms, which grow as cohesive expansile masses, that do not invade, infiltrate, or metastasize. They are usually encapsulated (capsule is made of a rim of compressed connective tissue derived largely from the native stroma). Nomenclature and classification 1. Tumors of mesenchymal origin: Designated by adding suffix “oma” to the cell of origin, e.g., fibroma, osteoma, and chondroma. 2. Tumors of epithelial origin are variously classified: (a) Some based on the cell of origin, e.g., squamous cell carcinoma. (b) Others based on the microscopic architecture, e.g., adenoma (glandular pattern), papilloma (finger-like or warty projections), cystadenoma, (cystic masses), and papillary cyst adenoma (papillary cystic masses). 3. Mixed tumors: Divergent differentiation of a single line of parenchymal cells resulting in tumors comprised of more than one cell type; usually derived from one germ cell layer, e.g., pleomorphic adenoma of salivary gland. Q. Define a teratoma. Ans. Tumor derived from a variety of cell types representing more than one germ cell layer, usually all three. Characteristics It is derived from totipotent cells and is usually encountered in gonads. May rarely develop in sequestered primitive cell rests elsewhere. Q. Define a choristoma. Ans. An ectopic rest of normal tissue, e.g., a rest of adrenal cells under the kidney capsule and pancreatic rest in intestine. Q. Define a hamartoma. Ans. Aberrant differentiation may produce a mass of disorganized but mature, specialized cells/tissue indigenous to the particular site (thought to an anomalous development or a neoplasm in origin), e.g., hamartoma of the lung.Chapter-06.indd 116 7/25/2011 1:38:00 PM
  3. 3. Neoplasia 117 Q. Differentiate between a hamartoma and a neoplasm. Ans. Differences between a hamartoma and a neoplasm Features Hamartoma Neoplasm Definition Disorganized focal overgrowth Abnormal, excessive, of mature tissue indigenous to a unregulated, autonomous particular site proliferation of cells Behavior Always benign May be benign or malignant Degree of differentiation Well-differentiated cells, which Vary from well-differentiated to completely resemble normal poorly-differentiated anaplastic counterparts lesions Clonality Polyclonal Monoclonal Examples Vascular hamartoma Squamous cell carcinoma Q. Define differentiation? Ans. Differentiation is the extent to which neoplastic cells resemble comparable normal cells, both morphologically and functionally. Well-differentiated cancers show maturation or specialization of undifferentiated cells as they proliferate. Poorly-differentiated/undifferentiated cancers show proliferation without differ- entiation or maturation. Q. Define and classify malignant tumors. Ans. Malignant tumors may be: Mesenchymal or connective tissue in origin, e.g., sarcomas. Epithelial in origin, e.g., carcinomas, usually named after parent organ or tissue of origin, e.g., adenocarcinoma of intestine and squamous cell carcinoma of cervix. Poorly-differentiated or undifferentiated malignant tumors, e.g., cancers com- posed of undifferentiated cells or cells of unknown origin. Q. Define anaplasia. Enumerate the morphological features indicative of anaplasia. Ans. Anaplasia is defined as lack of differentiation; literal meaning is “reverse differen- tiation”. It is a hallmark of malignant transformation. Morphological features indicative of anaplasia Pleomorphism (variation in size and shape of cells). Anisonucleosis (variation in size of nuclei).Chapter-06.indd 117 7/25/2011 1:38:00 PM
  4. 4. 118 Concise Pathology for Exam Preparation Abnormal nuclear morphology: – Abundant and darkly staining (hyperchromatic) DNA. – Coarsely clumped chromatin. – Increased nucleocytoplasmic ratio (normal 1:4 to 1:6; may approach 1:1). Numerous mitoses with abnormal, atypical, bizarre, tri, quadri, and multipolar spindles. Loss of polarity (orientation of cells). Presence of the tumor giant cells. Q. Define dysplasia. Enumerate the steps in the course of progression of dysplasia to invasive cancer. Ans. Dysplasia (disordered growth) is defined as loss of architectural orientation of cells with respect to one another and presence of pleomorphism, nuclear hyperchro- matism, and mitoses Dysplasia Carcinoma in situ (dysplasia involving the entire thickness of the epithelium) Invasive carcinoma (frank invasion into the stroma by malignant cells) Note: Dysplasia does not definitely/always progress to invasive carcinoma. Q. Differentiate between dysplasia and anaplasia. Ans. Differences between dysplasia and anaplasia Features Dysplasia Anaplasia Definition Lack of uniformity of Lack of morphological and individual cells with functional differentiation of cells architectural distortion Behavior A potentially precancerous Anaplasia is usually a hallmark of condition, which may or may malignant transformation not progress to cancer Tissue involved Mainly epithelium Both epithelium and mesenchyme Cellular pleomorphism Present but usually low grade High grade and nuclear atypia Mitotic figures Present, usually not atypical Abnormal and atypical figures may be seen (tripolar, quadripolar, and multipolar spindles) Tumor giant cells Absent PresentChapter-06.indd 118 7/25/2011 1:38:00 PM
  5. 5. Neoplasia 119 Q. Differentiate between metaplasia and dysplasia. Ans. Differences between metaplasia and dysplasia Features Metaplasia Dysplasia Definition Reversible change in which Loss of uniformity of the individual cells one adult cell type (epithelial or (mainly epithelial) as well as lack of mesenchymal) is replaced by architectural orientation with respect to another adult cell type one another Cellular Usually not seen Present pleomorphism Nuclear atypia Usually not seen Hyperchromatic and abnormally large atypical nuclei may be seen Mitotic figures Few Many Orientation with Maintained Loss of ordered maturation as in respect to one dysplastic stratified squamous epithelium another (tissue architecture) Reversibility Reversible, if triggering factors May become irreversible if it involves are removed whole thickness of the epithelium Example Columnar to squamous Cervical intraepithelial neoplasia (CIN) epithelium in respiratory tract of chronic smokers Q. Write briefly on the biology of the tumor growth. Ans. Rate of growth of the tumor depends upon: – Doubling time of tumor cells (time taken by the tumor cells to double their volume or number of cells). – Growth fraction (fraction of the tumor cells that are in the replicative pool). – Rate at which cells are shed and lost in the growing lesion. Fast growing tumors have a high cell turnover (high rate of, both proliferation and apoptosis). The tumor growth is possible only if rate of proliferation is greater than rate of apoptosis. Most anticancer drugs act on cells, which are in the growth cycle. Tumors with high growth fraction are more susceptible to radio and chemo- therapy. Debulking with surgery and radiation shifts tumor cells from G0 to G1 phase. Rate of growth is proportional to level of differentiation of cells. Q. Differentiate between benign and malignant tumors. Ans. Contrasting features of benign and malignant tumorsChapter-06.indd 119 7/25/2011 1:38:00 PM
  6. 6. 120 Concise Pathology for Exam Preparation Features Benign Malignant Gross features Boundaries Encapsulated/well circumscribed Ill circumscribed/ unencapsulated Size Usually small Usually large Secondary changes Less frequent More frequent Surrounding tissue Compressed Invaded Microscopic features Pattern Resembles tissue of origin Poor resemblance to tissue of origin Polarity Retained Lost Anaplasia Absent Present Mitoses Present, few, typical Present, many, atypical as well as typical Tumor giant cells Rare, without atypia Common, with atypia Cytogenetic changes Rare Common Physiology of cells/function Maintained Lost Growth rate Low High Local invasion Rare Common Metastasis Absent Present Q. Define local invasion. Ans. Most cancers are accompanied by progressive infiltration and destruction of the surrounding tissue, referred to as local invasion. Q. Define metastasis. Write briefly on the various pathways of spread of the tumors. Ans. Tumor implants discontinuous with the primary tumor, confirm the malig- nant nature of a tumor, and are labeled metastases. All cancers metastasize with a few exceptions, e.g., basal cell carcinoma (rodent ulcer) and gliomas of the central nervous system, which are locally invasive and rarely metastasize. Pathways of spread of the tumors 1. Direct seeding of body cavities and surfaces: Penetration of a tumor into a natu- ral open field/space, e.g., pleural, pericardial, subarachnoid, and synovial. Some- times mucinous tumors of appendix and ovary (both benign and malignant) fill the peritoneal cavity with a gelatinous neoplastic mass called “pseudomyxoma peritonei”. 2. Lymphatic spread (a) There are numerous interconnections between lymphatic and vascular chan- nels, so emphasis on differentiating lymphatic and vascular dissemination may be purposeless. (b) Functional lymphatics are absent in tumors and lymphatic vessels located at the surface are sufficient for lymphatic spread.Chapter-06.indd 120 7/25/2011 1:38:00 PM
  7. 7. Neoplasia 121 (c) Lymphatic spread tends to follow natural routes of lymphatic drainage and is the usual route for dissemination of epithelial malignancies; sarcomas may also use this route. (d) Drainage of tumor cell debris and antigens may induce reactive hyperplasia and spread of tumor cells to regional lymph nodes. (e) A “sentinel” lymph node is defined as the first node in the regional lymphatic chain to receive lymph flow from the primary tumor. 3. Hematogenous spread (a) Typical of sarcomas but also seen in carcinomas. (b) Arteries have thick walls, are less penetrable than veins. (c) All portal blood flows to liver and all caval blood flows to lungs; therefore liver and lungs are the most frequently involved organs in hematogenous dissemination. (d) Cancers in the vicinity of vertebral column, e.g., thyroid and prostate, metastasize to the vertebrae via paravertebral plexus. Q. Write briefly on the epidemiology of malignant tumors. Ans. The most common malignant tumors in: Men: Prostate (oral cavity in India) Lungs Colon or rectum Leukemia and lymphoma Liver Women: Breast (cervix in India) Lung Colon or rectum Leukemia and lymphoma Ovary Children: Acute leukemia CNS tumors Lymphomas Neuroblastoma Bone sarcomas Epidemiological factors influencing neoplasia 1. Familial and genetic factors: (inherited predisposition to cancer). (a) Autosomal dominant inherited cancer syndromes: The autosomal dominant inheritance of a single mutant gene greatly increases the risk of developing a tumor. The inherited mutation is generally a point mutation occurring in a single allele of a tumor suppressor gene. Defect in second allele occurs in the somatic cell generally as consequence of deletion or recombination. Examples Retinoblastoma (RB) – 40% retinoblastomas are familial.Chapter-06.indd 121 7/25/2011 1:38:00 PM
  8. 8. 122 Concise Pathology for Exam Preparation – Carriers of a mutant form of RB suppressor gene, have a greater risk of develop- ing RB, usually bilateral. They also have a greatly increased risk of developing a second cancer, e.g., osteogenic sarcoma. Familial polyposis coli – Autosomal dominant inheritance. – Presents with polypoid adenomas at birth. – 100% conversion to familial polyposis coli by the age of 50 years. MEN syndrome – MEN I – Adenomas of pituitary, parathyroid, and pancreas. – MEN II-Medullary carcinoma thyroid, pheochromocytoma, and parathyroid tumor. Neurofibromatosis or von Recklinghausen disease – Autosomal dominant. – Manifests with neurofibromas and Café au lait spots. Li-Fraumeni syndrome: Results from germline mutation of P53. (b) Defective DNA repair syndromes (i) Defects in DNA repair and DNA instability. (ii) Four categories of DNA repair genes: – Mismatch repair genes. – Base excision repair genes. – Nucleotide excision repair genes. – Double strand break repair genes. (iii) Generally autosomal recessive in inheritance, e.g., xeroderma pigmen- tosa, ataxia telangiectasia, and Bloom’s syndrome. (iv) Xeroderma pigmentosa manifests with extreme sensitivity to UV radia- tion and predisposition to basal cell carcinoma, squamous cell carci- noma, and malignant melanoma. (v) Rarely autosomal dominant in inheritance, e.g., HNPCC (hereditary nonpolypoid colonic cancer caused by inactivation of a DNA mismatch repair gene). (c) Familial cancers: Cancer with a high frequency of occurrence within a family are called familial cancers. They have the following features: (i) Early age of onset. (ii) Multiple primary cancers in a single individual (such as bilateral breast cancer). (iii) No clearly identifiable pattern of transmission. (iv) Examples: Carcinoma of breast, colon, uterus, ovary, stomach, and sarcomas. 2. Racial and geographic factors Race Commonly seen cancers White Europeans Carcinoma skin, penis, cervix, and liver Japanese Carcinoma stomach Indians Oral and GIT cancers, carcinoma cervix, and breastChapter-06.indd 122 7/25/2011 1:38:00 PM
  9. 9. Neoplasia 123 3. Environmental and cultural factors (a) Cigarette smoking: Oral cancers, carcinoma larynx, esophagus, lungs, pancreas, and urinary bladder. (b) Alcohol abuse: Cancer of oropharynx, larynx, esophagus, and liver. (c) Industrial and environmental carcinogens: Arsenic, asbestos, benzene, vinyl chloride, and beta naphthylamine. (d) Diet: Following factors predispose to malignancies: (i) Overweight individuals. (ii) Deficiency of vitamin A, tocopherols, selenium, and zinc. (iii) Diet rich in animal fats; low in fiber content. (e) Age: Most cancers are seen after 5th decade; some cancers may be seen in childhood. (f) Sex: Males are more commonly affected, except in carcinoma breast, gallbladder, thyroid, and hypopharynx. Predisposing factors for specific malignancies Carcinoma cervix: Young age at first coitus, greater frequency of sexual inter- course, multiplicity of partners and multiparity contribute to increasing prob- ability of carcinoma cervix. Penile carcinoma: Rare in Jews and Muslims (because they are customarily circumcised). Cancer of cheek and tongue: Associated with betel nut and tobacco chewing. 4. Interactions between genetic and nongenetic factors Inherited variations (polymorphisms) in enzymes that metabolize procarcinogens to carcinogens can determine the susceptibility to cancer, e.g., polymorphisms in gene coding for P450 confers inherited susceptibility to lung cancer in smokers. 5. Nonhereditary predisposing conditions (a) Chronic inflammation and cancer: An increased risk of cancer has been noted in chronic inflammatory conditions, e.g., ulcerative colitis, Helicobacter pylori, gastritis, viral hepatitis, etc. Inflammation increases expression of cyclooxy- genase-2 (COX-2), which induces conversion of arachidonic acid into pros- taglandins, which in turn are found to be increased in cancers, e.g., colonic cancer. The role of COX-2 inhibitors in cancer treatment and the potential association between cancer and chronic inflammation is being explored. (b) Pre-cancerous conditions: Non-neoplastic disorders and certain benign neo- plasia, which have a well-defined association with cancer. These include: (i) Actinic or solar keratosis. (ii) Barrett’s esophagus. (iii) Leukoplakia of oral cavity, vulva, and penis. (iv) Chronic atrophic gastritis. (v) Paget’s disease of bone. (vi) Multiple villous adenomas of colon. (vii) Neurofibromatosis.Chapter-06.indd 123 7/25/2011 1:38:00 PM
  10. 10. 124 Concise Pathology for Exam Preparation (viii) Long-standing ulcerative colitis. (ix) Cirrhosis of liver. (x) Chronic bronchitis (heavy smokers) Increased incidence of cancer (xi) Chronic irritation of the oral cavity due to regenerative cell (xii) Old burn scar (Marjolin’s ulcer) replication Q. Write in detail on the molecular basis of cancer. Ans. Carcinogenesis is initiated by nonlethal genetic damage to a cell (mutation), which could be: (a) Inherited in germ line. (b) Acquired (due to chemicals, radiation, and viruses). This is followed by clonal expansion of the mutated cell. Determination of clonality based on: – Analysis of methylation patterns adjacent to the highly polymorphic focus of human androgen receptor gene (HUMARA). – Presence of specific translocations. There are four classes of regulatory genes, namely: – Growth promoting proto-oncogenes. – Growth inhibiting tumor suppressor genes. – Genes that regulate programmed cell death. – Genes involved in DNA repair. Proto-oncogenes: Dominant. Transform cells despite the presence of a normal counterpart. Tumor suppressor genes: Recessive. Both normal alleles of tumor suppressor genes must be damaged to transform cell. Genes regulating apoptosis and cancer: Apoptosis in a normal cell is guided by cell death receptor CD95. BAD, BID, BAX, and TP58 are proapoptotic. BCL-2 and BCL-X are antiapoptotic. Mutant form of BCL-2 gene is seen in B cell lymphomas, carcinoma breast, thyroid, and prostate. CD95 is depleted in hepatocellular carcinoma. DNA repair genes: Defects in DNA repair genes predispose to mutations (mutator phenotype). Both alleles of DNA repair genes must be inactivated to induce genomic instability (recessive inheritance).Chapter-06.indd 124 7/25/2011 1:38:00 PM
  11. 11. Neoplasia 125 Q. Differentiate between anti-oncogenes and proto-oncogenes. Ans. Differences between anti-oncogenes and proto-oncogenes Features Anti-oncogenes Proto-oncogenes Other name Tumor suppressor gene Precursor genes for oncogene Function It suppresses cell proliferation and It promotes normal cell growth and promotes differentiation and maturation differentiation of cells Inheritance Recessive. Homozygous inactivation, Dominant. Mutation in a single copy i.e., loss of both normal copies of gene is may lead to oncogenic conversion required for carcinogenesis Action Acts passively, i.e., cancer promoting Acts actively, i.e., gene products of genes dominate and lead to tumor oncogenes directly lead to tumor formation due to loss of normal function formation of anti-oncogene Examples P53, RB gene, BRCA-1 and 2, TGF-β, myc, N-myc, ErbB1/2/3 APC, WT-1, and NF Q. Enumerate the steps involved in carcinogenesis. Ans. Carcinogenesis is a multistep process. Acquired or Normal cell environmental DNA repair DNA damaging agents DNA damage INITIATION OF CELL Failure of DNA repair Inherited mutations Mutations in the genome of somatic cells Activation of growth Inactivation of tumor Abnormalities in genes promoting genes suppressor genes regulating apoptosis Decreased apoptosis PROGRESSION Clonal expansion Angiogenesis Additional mutations Malignant neoplasm Invasion/metastasisChapter-06.indd 125 7/25/2011 1:38:00 PM
  12. 12. 126 Concise Pathology for Exam Preparation Q. Write briefly on role of cyclins, CDK (cyclin-dependent kinases), and CDK inhibitors in regulating G1/S cell cycle transition. Ans. Role of cyclins, CDKs, and CDK inhibitors in regulating G1/S cell cycle transition: External signals (growth factors, integrins) Activation of MYC, RAS and other genes Synthesis of cyclin D Cyclin D + CDK4 form an active complex P16 1NK4 P21 RB phosphorylation in E2F/DP1/Rb complex (in its hypophosphorylated form, RB binds to and sequesters a transcription activator called E2F; Rb is removed from E2F by phosphorylation and free E2F is made available) Free E2F Cyclin E transcription Cyclin E Cyclin E/CDK 2 (active complex) P27 G1 S Note: The cell cycle is blocked by P21, P27, and P16 1NK4. Q. Write in detail on cancer related genes and their effect on cell growth. Ans. Alterations in the controlling genes, typically by mutation, are major genetic hall- marks of cancer and include: Excessive and autonomous growth: Involving growth promoting oncogenes. Refractoriness to growth inhibition: Involving growth suppressing anti-oncogenes. Evasion of cell death by apoptosis: Involving genes regulating apoptosis and cancer.Chapter-06.indd 126 7/25/2011 1:38:01 PM
  13. 13. Neoplasia 127 Avoiding cellular ageing: Involving telomeres and telomerase in cancer. Continued perfusion of cancer: Angiogenesis. Invasion and distant metastasis: Cancer dissemination. Damaged DNA repair system: Mutated genes and cancer. Cancer progression and tumor heterogeneity: Clonal aggressiveness. 1. Excessive and autonomous growth (a) Genes that promote autonomous cell growth in cancer cells are called onco- genes and their normal cellular counter parts are called proto-oncogenes. (b) Proto-oncogenes are physiologic regulators of cell proliferation and differ- entiation. (c) Oncogenes are mutated form of normal proto-oncogenes, different the latter from in following ways: (i) Presence of mutation in the structure of gene. (ii) Oncogenes have the ability to promote cell growth in the absence of normal mitogenic signals and induce cancer unlike proto-oncogenes. (iii) Overexpression of oncogenes promotes autonomous and excessive cellular proliferation. (d) Activation of oncogenes is induced by: (i) Point mutation and deletion, e.g., RAS oncogene in carcinoma bladder and pancreas. (ii) Chromosomal translocation, e.g., Philadelphia chromosome (transloca- tion of C-ABL proto-oncogene from chromosome 9 to chromosome 22) is seen in 95% cases of CML and translocation of C MYC proto-oncogene from chromosome 8 to chromosome 14 is seen in 75% cases of Burkitt’s lymphoma. (iii) Gene amplification, chromosomal alterations that result in increased number of copies of a gene, e.g., n-MYC in neuroblastoma and ERB-B2 in breast and ovarian cancer. (e) Oncoproteins are products of oncogenes, which resemble products of proto- oncogenes but are devoid of important regulatory mechanisms. They include: (i) Growth factors (GFs): – Polypeptides elaborated by many cells. – Normally act on another cell to stimulate its proliferation (paracrine action), e.g., PDGF: Glioblastomas. TGF-α: Sarcomas. FGF: Carcinoma bowel and breast. – Many cancer cells are capable of synthesizing the same growth factors, which stimulate their growth, e.g., osteosarcomas encode beta chain of PDGF and the same tumors also express receptors for PDGF.Chapter-06.indd 127 7/25/2011 1:38:01 PM
  14. 14. 128 Concise Pathology for Exam Preparation (ii) Growth factor receptors: Receptors for growth factors may undergo mutations or may be overexpressed Mutant receptor proteins deliver continuous signals Continuous activation of signal transducing proteins on the inner leaflet of plasma membrane Signal transduced from cytosol to nucleus via second messengers Activation of nuclear regulatory factors DNA transcription Examples ERB-B1 (EGF receptor) in squamous cell carcinoma. HER2 (also called ERB-B2) overexpression in carcinoma breast, lung, ovary, and stomach. (iii) Signal transduction proteins: Normal signal transduction proteins, which transduce signals from the GF receptors on the cell surface to the nucleus, may get mutated, e.g., – Mutated RAS (rat sarcoma) gene: Most common form of oncogene in human tumors; is a member of a family of small G proteins. Associated with carcinoma colon, lungs and pancreas. Inactive form of RAS protein is GDP bound Growth factors bind to extracellular receptor domain and activate the intracellular domain of the same Conformational changes and activation of RAS GDP Intrinsic GTPase activity of RAS may reconvert GTP into GDP; GAPS (GTPase activating proteins), also prevent GTP uncontrolled RAS activation Stimulation of RAF mitogen activated protein (MAP) kinase mitogenic cascade Cell proliferation – Nuclear regulatory molecules: MYC gene is involved in Burkitt’s lymphoma (translocation 8, 14), carcinoma lung, breast, and colon (mutation due to amplification). Normal MYC protein binds to DNAChapter-06.indd 128 7/25/2011 1:38:01 PM
  15. 15. Neoplasia 129 and regulates the cell cycle by transcriptional activation and its levels fall immediately after the cell enters the cell cycle. Persistent overexpression of MYC oncogene leads to autonomous cell proliferation. – Cell cycle regulatory proteins: Normal cell cycle is under control of cyclins and CDK A, B, E, and D. Checkpoint is G1 → S phase. Mutations in cyclins (particularly cyclin D) and CDKs (in particular CDK4) may aid in induction of cancer, e.g., “overexpression of cyclin D” in carcinoma breast, liver and mantle cell lymphoma and “amplification of CDK4” in multiple myeloma, glioblastomas, and sarcomas. 2. Refractoriness to growth inhibition (growth suppressing anti-oncogenes): Anti-oncogenes or tumor suppressor genes prevent entry of cells in mitotic pool and push cells into the G0 phase. Mutated anti-oncogenes behave like a growth promoting genes. (a) Retinoblastoma (RB) gene: (i) Situated on long arm of chromosome 13q14. (ii) Two forms; active and inactive. Active RB gene (hypophosphorylated) G1 S Inactive RB gene (hyperphosphorylated) (iii) Mutant form of RB gene is implicated in retinoblastoma, which may be of two types: – Familial Both normal alleles of RB gene must be inactivated for development of retinoblastoma. In familial cases one defective copy is in germline, the other is lost due to a somatic mutation (two hit hypothesis of Knudson). Increased risk of other cancers, e.g., osteosarcoma, carcinoma breast, colon, and lungs, is noted with familial retinoblastoma. – Sporadic More than half the cases are sporadic. Both normal RB alleles lost by somatic mutation in retinoblasts. (b) TP53 gene (P53): (i) Situated on short arm of chromosome 17. (ii) Called ‘protector of the genome’ because more than half of all human cancers harbor p53 mutation. (iii) Two major functions: – Blocking mitotic activity If the damage is minor, p53 halts the cell cycle/cell division, until the damage is repaired. It inhibits cyclins and CDKs and prevents cell from entering G1 phase transiently and this breathing time is utilized to repair DNA damage.Chapter-06.indd 129 7/25/2011 1:38:01 PM
  16. 16. 130 Concise Pathology for Exam Preparation – Role in promoting apoptosis If the damage is major and cannot be repaired, p53 triggers the cell to commit suicide by apoptosis (activates apoptosis, inducing BAX gene to bring the defective cell to an end). Mutated form of p53 behaves like an oncogene; induces carcinoma of lung, head, neck, colon, and breast. Also, contributes to sequential development of carcinoma in situ in invasive carcinoma. Cancers of multiple organs (breast, bone, and brain sarcomas) are caused by damage to both alleles (Li-Fraumeni syndrome). (c) Transforming growth factor- (i) Inhibitor of cell proliferation. (ii) Acts on G1 phase. (iii) Mutant form has impaired growth inhibiting effect, leading to uncon- trolled cell proliferation and cancer, e.g., carcinoma pancreas, colon, and stomach. (d) Adenomatous polyposis gene (APC): APC gene is a cytoplasmic protein called β catenin, which blocks the signal to the nucleus for activating mitosis. In colonic carcinoma loss of APC gene leads to uninhibited growth. (e) WT-1 gene: (i) Prevents neoplastic proliferation of cells in embryonic kidney. (ii) Mutant form implicated in Wilms’ tumor. (f) Neurofibroma (NF) gene: (i) Prevents proliferation of Schwann cells. (ii) Involved in neurofibromatosis-1 and 2. (g) BRCA1 and BRCA2: (i) Breast cancer susceptibility genes. (ii) BRCA1 gene is located on the long arm of chromosome 17 and its protein product is involved in DNA damage repair and transcriptional regula- tion. (iii) Variations in the gene have been implicated in a number of hereditary cancers, namely breast, ovary and prostate. (iv) BRCA2 gene is located on the long arm of chromosome 13 and is essen- tial for repairing damaged DNA; the BRCA2 protein binds to and regu- lates the protein produced by the RAD51 gene to fix breaks in DNA. (v) Abnormalities of the BRCA2 gene may cause an increased risk of breast cancer along with cancer of the ovaries, prostate, and pancreas and malig- nant melanoma. (h) VHL gene: Germline mutation of von Hippel–Lindau gene on chromosome 3p is associated with hereditary renal cell carcinoma, pheochromocytoma, hemangioblastomas of the central nervous system, retinal angiomas, and renal cysts. Mutations in VHL gene are sometimes also noted in sporadic renal cell cancers. (i) PTEN: Phosphatase and tensin homologue (PTEN) located on chromosome 10. This gene is frequently deleted in endometrial cancer and glioblastoma.Chapter-06.indd 130 7/25/2011 1:38:01 PM
  17. 17. Neoplasia 131 (j) Cadherins (i) Cadherins are a family of transmembrane proteins that play an important role in cell adhesion. They are dependent on calcium ions to function, hence their name. (ii) Loss of cadherins allows easy disaggregation of cells, which can invade locally as well as metastasize. (iii) Different members of the cadherin family are found in different loca- tions. E cadherins are found in epithelial tissue; N cadherins are found in neurons; and P cadherins are found in the placenta. (iv) Reduced cell surface expression of E cadherins is noted in many types of cancers, e.g., esophagus, colon, breast, and ovary. (v) Germline mutations of E cadherin gene predisposes to familial gastric carcinomas. (k) KLF6: Encodes a transcription factor that has many target genes including TGF-β and TGF-β receptors, mutated in more than 70% of primary prostate cancers. Q. Write briefly on angiogenesis. Ans. Angiogenesis is defined as growth of new blood vessels. Tumor angiogenesis is necessary for tumor perfusion and bringing in nutrients and growth factors that stimu- lates the growth of adjacent cells. New vessels sprouting from already existing ones, is called neoangiogenesis. In vasculogenesis, endothelial cells are recruited from the marrow. Endothelial cells secrete GFs, which promote the growth of tumor cells. Angiogenesis also gives access to vasculature and thus aids in metastasis. Promoters of angiogenesis include VEGF, angiopoietins 1 and 2, and β-FGF. Inhibitors of angiogenesis include thrombospondin-1, angiostatin, and endostatin. Q. Describe the mechanism and biology of invasion and metastasis. Ans. Development of a rapidly proliferating clone of cancer cells Emergence of a subpopulation of tumor cells with the requisite biological characteristics for metastasis Adhesion to and invasion of basement membrane Tumor cell-ECM interactions and degradation of ECM due to: • ↑ Metalloproteinase expression on tumor cells • ↑ Proteases • ↓ Inhibitors of metalloproteinases (TIMPs)Chapter-06.indd 131 7/25/2011 1:38:01 PM
  18. 18. 132 Concise Pathology for Exam Preparation Invasion of ECM Neoangiogenesis Development of leaky blood vessels with endothelial gaps having direct contact with cancer cells Intravasation (entry into vessels) Interaction with host lymphoid cells to form tumor cell embolus Adhesion to basement membrane of vessel wall Extravasation at a distant site Metastatic deposit Proliferation as a secondary colony aided by angiopoietins 1 and 2 Q. Write briefly on chemical carcinogenesis. Ans. Induction of cancer depend on: Dose, duration, and mode of administration of the chemical. Individual susceptibility. Associated predisposing factors. Stages Initiation – Results from exposure of cells to sufficient dose of the carcinogen. – Change induced is sudden and irreversible. Promotion – Promoters include phorbol esters, phenols, hormones, artificial sweeteners, and phenobarbital. – Lead to proliferation and clonal expansion of the altered and initiated cell. Initiators Direct acting carcinogens – Alkylating agents Anticancer drugs, e.g., cyclophosphamide, chlorambucil, busulfan, melphalan, and nitrosoureas. Beta propiolactone. Dimethyl sulphate. Diepoxybutane.Chapter-06.indd 132 7/25/2011 1:38:01 PM
  19. 19. Neoplasia 133 – Acylating agents 1-acetyl imidazole. Dimethyl carbamyl chloride. Indirect acting (procarcinogens) – Polycyclic aromatic hydrocarbons: Found in tobacco, smoke, fossil, fuel, soot, tar, mineral oils, and smoked animal foods. Anthracenes Cause lung and skin cancer, Benzopyrene cancer of oral cavity, and Methylcholanthrene sarcomas – Aromatic amines and azo dyes β naphthylamine Benzidine Cause urinary bladder and Azo dyes (butter yellow, scarlet red) hepatocellular carcinoma – Naturally occurring products Aflatoxin B1 (causes hepatocellular carcinoma). Cycasin. Safrole. Betel nuts. – Miscellaneous Nitrosamines and amides (cause gastric carcinoma). Vinyl chloride monomer (cause angiosarcoma of liver). Asbestosis (cause bronchogenic carcinoma, mesothelioma). Nickel, lead, cobalt, and chromium (cause epidermal hyperplasia, and basal cell carcinoma). Procarcinogen Biotransformation of procarcinogen in endoplasmic reticulum of hepatocytes by mono-oxygenases of cytochrome P450 Carcinogen Conversion into electron deficient electrophiles Initiation Binding of electrophiles to electron rich portions of cell (DNA, RNA and proteins); target molecule chiefly DNA • Permanent DNA damage, leading to initiation cell • Altered cell undergoes at least one cycle of proliferation in order to transfer the change to the progeny Promotion Clonal proliferation of altered cell NeoplasmChapter-06.indd 133 7/25/2011 1:38:01 PM
  20. 20. 134 Concise Pathology for Exam Preparation Mechanism: Indirect acting carcinogens require metabolic activation: Q. Differentiate between initiators and promoters. Ans. Contrasting features of initiators and promoters Features Initiators Promoters Sequence of application Applied first Applied after initiator Mechanism Induction of mutation Not mutagenic; instead are mitogenic. Induce cell cycling and reinforce the action of initiators rather than inducing a mutation Dose Single for a short time Repeated over a long time Response Sudden Delayed Molecular change Permanent/irreversible Reversible Examples Most chemical carcinogens, Hormones, phorbol esters radiation Q. Write briefly on microbial carcinogenesis. Ans. Microbial carcinogenesis is mainly induced by oncogenic viruses and bacteria like Helicobacter pylori. 1. Oncogenic DNA viruses: Genome of oncogenic DNA viruses integrates into and forms stable associations with host genome, e.g., E6 proteins of high-risk HPV types complex with p53 to enhance its degradation. Oncogenic DNA viruses include: (a) Human papilloma virus (HPV): More than 100 distinct subtypes. (i) 1, 2, 4, 7 cause benign squamous papillomas (warts). (ii) Malignancies associated with HPV are squamous cell carcinoma (SCC) of cervix and anogenital region, oral and laryngeal cancers. (iii) HPV 16, 18, 31, 33, 35, 51 are associated with SCC and precursors lesions. (iv) HPV 6, 11 cause genital lesions with low malignant potential. (v) HPV genome is present in episomal (nonintegrated) form in benign warts and pre-neoplastic lesions. (vi) In cancers, viral genome is integrated in host DNA. Effects of HPV proteins on cell cycle HPV E6 and E7 block p53 and RB cell cycle suppression pathways, respectively. E6 proteins of high-risk types complex with p53 to enhance its degradation. E6 proteins of low-risk types have low affinity for p53 and do not affect its stability. Increased p53 degradation causes a block in apoptosis (p53 increases activity of BAX, which is pro-apoptotic). E7 from high-risk types binds to RB protein, releasing sequestered E2F from the Rb-E2F complex, triggering entry of cells in the S phase. E7 from low-risk types has a lower affinity for RB protein and is slow in transform- ing cells.Chapter-06.indd 134 7/25/2011 1:38:01 PM
  21. 21. Neoplasia 135 (b) Epstein–Barr virus (EBV): Implicated in the pathogenesis of: (i) African form of Burkitt lymphoma. (ii) B cell lymphoma in immunosuppressed individuals. (iii) Hodgkin’s lymphoma. (iv) Nasopharyngeal carcinoma. (v) Gastric carcinoma. (vi) NK cell lymphoma. Mechanism EBV attaches to/infect cells of oropharynx and B lymphocytes via CD21 Linear genome of EBV circularizes to form an episome in B cells Normal immune system keeps infected cells in check Latent infection of B cells Decreased immunity/evasion of immune system Activation of EBNA-2 LMP-1 induces the NFkB and JAK/STAT signaling pathways LMP-1 Cyclin D B cell activation via CD40 B cells G0 G1 Promotes B cell survival and proliferation Actively dividing B cell population is at increased risk of developing mutations, e.g., translocation (8; 14) Juxtaposition of MYC with lg gene and activation of MYC gene Uncontrolled proliferation Note: LMP-1 is latent membrane protein-1. (c) Hepatitis viruses (i) 70–80% hepatocellular carcinoma is due to HBV and HCV. (ii) Effect of HBV may be indirect; causes chronic liver cell injury, and regen- erative hyperplasia (increased pool of cycling cells at risk for genetic changes). (iii) HBV also encodes a regulatory element called HBX protein, which disrupts normal growth control of infected liver cells by transcriptional activation of:Chapter-06.indd 135 7/25/2011 1:38:01 PM
  22. 22. 136 Concise Pathology for Exam Preparation – Insulin-like growth factor II and receptors for insulin-like growth factor I. – Binds to P53 and interferes with its growth suppressing activities. (d) HHV 8 (human herpes simplex virus 8) (i) Role in: Kaposi’s sarcoma, B cell lymphomas, and multicentric variant of Castleman’s disease. (ii) HHV 8 infects host macrophages and primitive mesenchymal cells, which differentiate into endothelial cells under the influence of several cytokines like IL6, IL8, MIP α, etc. 2. Oncogenic RNA viruses (a) Retroviruses are the only RNA viruses, which seem to have oncogenic poten- tial in humans. (b) Contain “reverse transcriptase”, which induces reverse transcription of viral RNA to synthesize viral DNA. (c) The viral DNA moves to host cell nucleus and gets incorporated in it. Examples: HTLV-I Associated with a form of T cell leukemia–lymphoma endemic in Japan and Caribbean basin. HTLV-I has tropism for CD4+ T cells. Transmission of infected T cells occurs via sexual intercourse, blood products, and breast feeding. Contains gag, pol, and env genes typical of other retroviruses. Also contains “TAX” gene, which activates several host cell genes involved in prolif- eration and differentiation of T cells and interferes with DNA repair functions. 3. H. pylori (a) Present in 90% cases of gastritis and 20–30% cases of gastric ulcer. (b) May be associated with gastric carcinoma and gastric lymphomas. (c) Induces active B cell proliferation, which predisposes to acquisition of genetic abnormalities, e.g., translocation (11; 18). Chronic gastritis Multifocal atrophy and decreased gastric acid secretion Intestinal metaplasia Dysplasia Carcinoma (adenocarcinoma of intestinal type)Chapter-06.indd 136 7/25/2011 1:38:01 PM
  23. 23. Neoplasia 137 Q. Differentiate between DNA and RNA oncogenic viruses. Ans. Differences between DNA and RNA oncogenic viruses Features DNA oncogenic virus RNA oncogenic virus Viruses HPV, EBV, HBV, KSHV HTLV-1 Genome Double-stranded DNA Single-stranded RNA Reverse transcriptase Absent Present Interaction with host Linear DNA genome forms a double- First RNA is transcribed into DNA, genome stranded circle within infected cell and which then integrates into host then covalently integrates into host genome genome Name of gene Early region A gene src gene Name of protein T antigen src protein Function of protein Protein kinase, ATPase activity, Protein kinase that phosphorylates binding to DNA and stimulation tyrosine and disturbs the growth of DNA control process Location of protein Primarily nuclear, but sometimes in Plasma membrane plasma membrane Q. Define and describe paraneoplastic syndromes. Ans. Symptom complex in patients with cancer that cannot be explained either by local or distant spread of the tumor or by the elaboration of hormones indigenous to the tissue of origin of the tumor is known as paraneoplastic syndrome. Appears in 10–15% patients with cancer. Important to recognize because: – May be the earliest manifestation of occult or hidden cancer in some cases. – May represent clinical problems due to excessive production of that hormone. – May manifest with metastatic disease. Can be classified into: – Endocrinopathies. – Nerve and muscle syndrome. – Dermatological disorders. – Vascular and hematological changes. – Bone and soft tissue changes. 1. Endocrinopathies (a) Ectopic hormone/hormone-like substance is produced by cells of nonendo- crine origin. (b Small cell carcinoma of lung, pancreatic carcinoma, or neural tumors produce ACTH or ACTH-like substance resulting in Cushing’s syndrome. (c) Squamous cell carcinoma of lung, carcinoma of breast, kidney, and ovary pro- duce excess of parathormone or related hormones, TNF- , TGF- , IL-1 causing hypercalcemia (most common paraneoplastic syndrome).Chapter-06.indd 137 7/25/2011 1:38:01 PM
  24. 24. 138 Concise Pathology for Exam Preparation (d) Gastric and bronchial carcinoid syndromes are produced by elaboration of serotonin and bradykinin by bronchial adenoma, pancreatic carcinoma, and gastric carcinoma. 2. Nerve and muscle syndrome (a) Immunologically-mediated myasthenia gravis in bronchogenic carcinoma. (b) Disorders of the central and peripheral nervous system seen in breast carcinoma. 3. Dermatological disorders (a) Acanthosis nigricans may be seen in carcinoma of the lung, uterus, and stomach. (b) Dermatomyositis may be seen in bronchogenic and breast carcinoma. 4. Vascular and hematological changes (a) Tumor products (usually mucins that activate clotting factors) induce venous thrombosis (Trousseau sign), in pancreatic and bronchogenic carcinoma. (b) Nonbacterial thrombotic endocarditis (due to hypercoagulability) is seen in advanced cancers. (c) Anemia may develop in association with thymic neoplasms (unknown cause). 5. Bone and soft tissue changes: Hypertrophic osteoarthropathy and clubbing may be seen in bronchogenic carcinoma (unknown cause). Q. Write briefly on laboratory diagnosis of cancer. Ans. The modalities for laboratory diagnosis of cancer include: 1. Cytology Direct (a) Fine needle aspiration cytology (FNAC) Image guided Air-dried MGG (May Grunwald Giemsa) stained smears or wet fixed (95% ethanol fixed) hematoxylin and Eosin stained smears are be prepared and examined. (b) Exfoliative cytology: Due to loss of cohesiveness, neoplastic cells are continu- ously shed from tumors into the surrounding space. These are called exfoliated cells and may be seen in: (i) Papanicolaou smears for carcinoma cervix. (ii) Sputum and bronchial washings for bronchogenic carcinoma. (iii) Pleural, pericardial, and peritoneal fluid (for local cancers). (iv) Urine for urothelial malignancies. (v) CSF (for CNS tumors). (vi) Gastric secretions for gastric carcinoma. Diagnostic reliability of exfoliative cytology varies between 80–97%. 2. Histopathology: (a) Microscopy supported by clinical and investigative data. (b) Formalin fixation is required for routine histopathology and glutaraldehyde fixation is required for electron microscopy. (c) Frozen section aids in rapid/intraoperative diagnosis.Chapter-06.indd 138 7/25/2011 1:38:02 PM
  25. 25. Neoplasia 139 3. Histochemistry/cytochemistry (special stains): These are diagnostic tools for identifying chemical composition of cells, for the purpose of tumor diagnosis and classification. Substances Stain Basement membrane/collagen PAS Reticulin Van Gieson Masson’s trichrome Glycogen PAS with diastase loss Glycoproteins PAS Mucins of epithelial origin Mucicarmine Acid mucins (of mesenchymal origin) Alcian blue Argyrophilic/argentaffin granules/fungi Silver stains Fat Oil Red O, Sudan black B 4. Immunohistochemistry/Immunocytochemistry: (a) Immunological method of recognizing a cell, based on recognition of specific components called “antigens”. (b) “Specific antibodies” against antigens raised by hybridoma technique and labeled monoclonal antibodies are used for diagnosis. (c) Antigen-antibody complexes on the slide made visible for microscopic identi- fication by labels (fluorochromes or enzyme systems). Uses Categorization of undifferentiated neoplasms. Specific typing of leukemias/lymphomas. Determination of site of origin of a metastatic tumor. Detection of molecules that have prognostic or therapeutic significance, e.g., ER-PR receptors in carcinoma breast. Expression of protein products of oncogenes. Differentiating benign from malignant lesions. “Intermediate filaments” (cytoskeletal elements formed by a family of related proteins, which enhance structural integrity and stability of cells) and their significance in the tumor diagnosis: Keratins Carcinomas, mesotheliomas, and germ cell tumors Vimentin Sarcomas, melanomas, and lymphomas (mesenchymal tumors) Desmin Myogenic tumors Neurofilaments Neural tumors Glial fibrillary acidic proteins Glial tumors 5. Electron microscopy: Used for confirming or substantiating tumor diagnosis. Based on: (a) Presence and type of cell junctions. (b) Presence of microvilli.Chapter-06.indd 139 7/25/2011 1:38:02 PM
  26. 26. 140 Concise Pathology for Exam Preparation (c) Shape of nucleus, features of nuclear membrane, and nucleoli. (d) Cytoplasmic organelles. (e) Presence of dense bodies in the cytoplasm. 6. Tumor markers (substances found in blood, urine, body fluids, or tissue, the levels of which might be elevated in association with a cancer). AFP (alpha fetoprotein) Hepatocellular carcinoma, nonseminomatous germ cell tumors PSA (prostate-specific antigen) Prostatic carcinoma HCG (human chorionic gonado- Trophoblastic tumors tropin) Calcitonin Medullary carcinoma thyroid Pheochromocytoma Vanillylmandelic acid (VMA) CA-125 Carcinoma ovary CEA (carcino embryonic antigen) Cancer of bowel, pancreas, and breast CA-15.3 Carcinoma breast Used for 1. Pathological diagnosis. 2. Prognostic and therapeutic purposes. 7. Modern aids in the tumor diagnosis: (a) Flow cytometry: Recognition and quantification of several parameters simul- taneously by making single cell suspensions of cells, which are made to pass through a chamber in a single file. Fluids, blood, and bone marrow can be processed directly whereas homogenization is necessary for solid tissue. Each cell is struck by a focused laser beam and the properties of scattered and fluo- rescent light is measured to characterize the cell. DNA content (aneuploidy is associated Material is analyzed for with poor prognosis) Identification of cell surface antigens (b) In situ hybridization: Molecular technique by which nucleic acid sequences (cellular/viral DNA and RNA) are localized, by specifically labeled nucleic acid probes directly in the cell rather than after DNA extraction, e.g., localization of oncogenes. (c) Other molecular diagnostic techniques: Variety of DNA-/RNA-based techniques in which DNA/RNA are extracted and analyzed, e.g., DNA analysis by Southern blot and RNA analysis by Northern blot. Used for Analysis of molecular cytogenetic abnormalities. Analysis of mutations. Analysis of antigen receptor gene rearrangement. Study of oncogenic viruses at the molecular level.Chapter-06.indd 140 7/25/2011 1:38:02 PM