3. Carcinomas
Definition: malignant tumors of epithelial origin
Incidence: most common class of tumors (contributing about 80% of cases)
Age: most common in middle and old age
Growth rate: slow, hence, carcinomas are smaller in size than sarcomas
Gross margin: irregular
Histologically: composed of cohesive groups infiltrating distinct stroma, such
cohesive pattern was proved by EM to be due to presence of surface
attachment structures (desmosomes) & interdigitating cell membranes
Spread
* Lymphatic spread: main & early route of spread
* Blood spread: late, commonly affecting liver, lungs, brain, bone
4. Include
1) Squamous cell carcinoma
* Arises from skin, upper areodigestive tract, anal margin, vagina, uterus
* May arise in areas of squamous metaplasia such as lungs, urinary tract, gall
bladder
* L/M: cytoplasmic keratinization, nests in well-differentiated tumors
2) Transitional cell carcinoma
* Occur in urinary passages, nasal cavity, paranasal sinuses
* Tumor cells have undifferentiated cytoplasm
3) Adenocarcinomas
* Arises from columnar epithelium: surface epithelium (e.g. respiratory,
gastrointestinal) or from glands (e.g. liver, prostate)
5. * May arise on top of columnar epithelial metaplasia (urinary bladder,
esophagus)
* L/M: acinar or ductal formation, eccentric nuclei, clear cytoplasm, mucin
secretion; intracellular (signet-ring cells ) or extracellular
4) Choriocarcinoma
* Refers to fetal or gestational type which affects uterus
* L/M: biphasic structure with presence of both cyto & syncytial
trophoblastic epithelium
6. Sarcomas
Definition: malignant tumors of mesenchymal origin
Incidence: contributing about 8% of all malignant tumors
Age: affect all ages, including children
Rate of growth: rapid hence they present as bulky mass
Gross: circumscribed tumors, with pseudocapsule of compressed normal tissue
Histologically: sarcoma cells are scattered in distribution & indistinct from stroma due
to absence of desmosomes & cell membrane attachments
Behavior
* Diversity of tumor subtypes (multiple cell differentiation, interconversion)
* Site specificity of bone tumors
Spread: Sarcomas spread mainly by blood, lung being most common site of metastases
Include: soft tissue & bone sarcomas
7. Carcinomas Sarcomas
Definition Malignant tumor of epithelial
cells
Malignant tumor of
mesenchyma
Incidence More common Less common
Age Old age Young age
Growth rate Less rapid Rapid
Gross picture Fungating, ulcerative,
infiltrating
Bulky mass
Consistency Hard Fleshy
Vascularity Less vascular Highly vascular
Necrosis Less necrosis Marked
Microscopic Cells arranged in groups é
stroma inbetween
Cells arranged singly é
matrix inbetween
Spread Delayed Early
Distant spread Mainly by lymphatics Mainly by blood
8. Neuroectodermal tumors
Classified according to cell differentiation into three main groups:
1) Differentiated neuroectodermal tumors (DNET): malignant melanoma,
neurofibrosarcoma, gliomas, meningiomas
2) Neuroendocrine tumors (NET)
* Epithelial NET: carcinoid tumor, small cell undifferentiated carcinoma,
medullary carcinoma of thyroid, Merkel's cell carcinoma of skin
* Neural NET: neuroblastoma, pheochromocytoma, paragangliomas
3) Primitive neuroectodermal tumors (PNET)
* Central PNET: medulloblastoma, pineoblastoma, cerebral neuroblastoma,
olfactory neuroblastoma
* Peripheral PNET: affect bone or soft tissue (Ewing's/PNET)
10. Germ Cell Tumors
Arise in: abnormal or dysgenetic gonads
Arise from: diploid germ cell prior to its reduction division
Tumor types: according to different maturation pathways
1) reproduction of germ cells without differentiation
2) differentiation to primitive embryonic epithelium
3) differentiation to reproduce embryonic structures representative of 3 germ cell layers
4) differentiation to extraembryonic structures
Include
1) Seminoma
2) Dysgermonoma
3) Embryonal carcinoma
4) Malignant teratoma
5) Yolk sac tumor
6) Choriocarcinoma
11. Tumors of Blastemal
Consist of: cellular elements present in the particular location
Age: some of these tumors are present at birth, most develop within 1st 5 years of life
Histogenetically
* Clone of cells fail to mature during development & retains its undifferentiated
embryonic nature (blastemal cell rests)
* Tumors may be composed of one cell type (monophasic), or may be composed of
multiple cell types (biphasic, triphasic)
Include
1) Nephroblastoma
2) Retinoblastoma
3) Neuroblastoma
4) Hepatoblastoma
5) Pancreaticoblastoma
12. Tumors of Vestigeal Remnants
Origin: during embryonic development, certain structures are temporarily produced
which normally undergo atrophy. However, if parts of them remain, tumors may
develop from these remnants
Include
1) Chordoma
2) Ameloblastoma
3) Branchiogenic carcinoma
4) Urachal carcinoma
5) Mesonephroma
6) Mullerian carcinosarcoma
13. Tumors of Uncertain Origin
Composed of: peculiar cells which do not correspond to any of known embryonal or
adult cells, hence, they are named by cytomorphologic terms. They often exhibit a
complex multi-lineage immunohistochemical reactions including epithelial,
mesenchymal &/or neuroectodermal differentiation
Include
1) Malignant rhabdoid tumor
2) Alveolar soft part sarcoma
3) Epithelioid sarcoma
4) Desmoplastic small cell tumor
14. Undifferentiated Tumors
Tumor cells: anaplastic so it is difficult to classify under any of mentioned cell types
Classified as: small cell, spindle cell, pleomorphic large or giant cell types
Origin
* De novo undifferentiated
* Dedifferentiated: represent focal progression in previously differentiated tumor