Neoplasm's are also known as tumors (swelling) but all swellings are not neoplasms e.g. parasitic nodules, cold abscesses, chronic inflammations(tuberculosis, glanders). These swellings subside after the causative agent is removed while neoplasms grow continuously & indefinitely.
In inflammation and repair cells proliferate; but then there is a purpose for proliferation i.e. to protect and replace tissues. As soon as the need is fulfilled proliferation ceases and growth even regresses.
Neoplasm and hyperplasia
Hyperplasia results due to proliferation of cells of tissues from a definite demand. E.g. proliferation of surviving cells in a excised or damaged liver or kidney, erythropoietic tissue in anemia, hyperplasia of leucopoitic tissue during acute inflamation resulting into leucocytosis, thyroid gland in goitre, of mammary gland and prostrate when respective hormones are in excess.
Oncogenic RNA viruses like Feline leukemia virus transmitted horizontally and having reverse transcriptase enzyme make DNA copies from viral RNA & incorporate it into host cell DNA for replication & cells may get transformed causing lymphoma, erythroleukomia and myeloproliferative diseases, Feline sarcoma virus, avain sarcoma virus, avain leucosis virus
oncogenic DNA viruses like canine oral papilloma virus causes multiple wart like masses on the mucous membranes and tongues of dogs on contact, papovavirus cause cutaneous papilomas in dog.
UV-radiation from sun is the only significant form of radiation causing spontaneous cancer in domestic animals. White cats, collie & Shetland sheepdog are susceptible to UV-radiation induced squamous carcinoma on unpigmented areas,
hemangiomas and hemangiosarcomas in beagles.
x-rays and radioactive isotopes(beta & gamma emitters) can cause experimental neoplasm's in dog & cat.
chronic irritation, repeated trauma or trauma with concurrent tumor stimulating factors result in
After invasion has occurred tumors may metastasize by;
Direct extension / infiltration in adjacent organs.
Transplantation/transcoelomic migration into body cavities by seeding of exfoliated cells from primary tumor to serosal surface of abdomen or migration around blood vessels passing through diaphragm allowing implantation in pleural cavity.
Lymphatic system- by permeation or embolism most common method in many carcinomas.
Hematogenous route- by invasion into thin walled veins. Arteries relatively resistant. Lungs are most preferred sites for hematogenous
metastasis since they receive & filter all the venous blood before returning it to heart, followed by liver.
e) Implantation- by
Natural passage- tumor cells growing on surface of hollow organs may cast into lumen & may be implanted in other areas e.g. cells from renal pelvis carcinoma may be washed down to bladder & implanted there. Likewise tumors of bronchi & bowel may be implanted in other parts of bronchial tree & bowel respectively.
Inoculation- it’s a rare hazard in surgery where neoplastic cells are implanted on edges of a wound which develops into a new tumor.
clinical - any rapidly growing tumor bleeding profusely & does not heal must arouse suspicion of cancer.
Biopsy - cytological exam. Of tumor aspirate may reveal anaplasia, invasion & loss of polarity in malignancy. Most reliable method.
Radiology -possible in viscera & bone.
Exfoliative cytology _ cancer cells cling together less firmly than normal cells & those at surface when cast off (exfoliate) can be collected, stained and diagnosed. Used in humans for uterine & bronchiogenic cancer. first used by Papanicolou so named as PAPA’s test.
8 . Paraneoplastic effects – any effect not caused directly by the tumor or its metastasis & includes topic hormone production by cells of endocrine tumors, ectopic hormone ( by derepression of genes) production by cells of non-endocrine tumors & production of various biochemical substances by cancer cells.
Palliative procedures- to increase life of a patient through local reduction of tumor mass in spite of local invasion or metastasis e.g. repeated removal of fibrosarcomas recurring locally ameliorate the clinical signs & allow animal to live a fairly comfortable life for several months to years.
Amputation of limb with osteosarcoma may also be included in this.
Exploratory procedures- in establishing diagnosis & prognosis like exploratory celiotomy, or thoracotomy to confirm or rule out a suspicion of neoplasia based on history, physical exam, laboratory data, & radiographs.
Combination therapies- surgeon becomes a member of multidisciplinary team that includes immunologists, radiologists, pathologists, pharmacologists & biochemists in decreasing the tumor load.
surgical removal increases immunocompetence.
Residual microfoci of tumor cells more sensitive to chemotherapy & immunotherapy than primary tumor bcoz metastasis have a better blood supply & more rapid rate of cell turnover.
Surgery as immunotherapy- neoplasm's limit the hosts immune system by producing specific & nonspecific immunosupression of cancer patient by constantly shedding soluble tumor associated antigens into blood which circulate alone or as Ag-Ab complexes & inhibit lymphocyte mediated destruction of tumor cells.
Also cause nonspecific generalized immunosupression of patient.
Immunosupression correlates with the stage of disease & size of tumor burden.
Surgical maneuver lowers tumor mass & reverses both specific & nonspecific immunosupression increasing
Radiography of regional bones & thoracic cavity to rule out metastasis.
Tumor type, presence or absence of metastatic disease, location of neoplasm, appearance & function of animal after surgery, owner considerations including cost & clients emotional wellbeing and wishes.
Use of any or all components of hosts immune system to control, damage, or destroy malignant cells.
Interest in IT appeared after demonstration of tumor specific antigen in chemically induced neoplasms in mice so was assumed that similar antigens would be found in spontaneous tumors in man & animals.
Evidence of significace of immune system on tumor behavior ;-
Increased incidence of tumors in congenitally immunosuppressed humans or animals.
Demonstration of blocking factors(Ag-Ab complexes )
Active specific immunotherapy by tumor vaccines prepared from TSA or modified or killed preparations of whole cells.
Passive immunotherapy by administration of immune sera, immune lymphocytes, specific antibodies, complement, immune RNA preparations & monoclonal antibodies.
Non-specific immunotherapy by biological modulators like MBV,BCG, corynebacterium parvum & c .granulosum, vaccinia virus, freunds adjuvent. Chemical immunostumilators like levamisol, DNCB, MDP, azimexon & tuftsin.
Degree of cell killing depending on temperature & duration of heating.
Increase in heating time- rate of
killing is exponential.
Hyperthermia is a specialized therapy that involves heating selected tumors to 106 to 108 ̊F for up to one hour. Hyperthermia can be delivered in combination with radiotherapy .Cancers most commonly treated with hyperthermia are head and neck, prostate, cervical, skin soft tissue sarcoma, and chest wall recurrences of breast cancer.
Certain cancer cells can become resistant to cancer treatment when they become oxygen-starved due to poor blood supply. Heat application causes increased blood flow and oxygen to the tumor making the cancer cells more susceptible to cell death. Hyperthermia is always preceded or followed by radiation or chemotherapy because it enhances the effectiveness of these treatments.
Hyperthermia can be delivered externally or internally. An external device, similar to a heating pad, is used for tumors close to the skin’s surface. For all others, small wires are inserted into surgically implanted hollow tubes and energized with microwaves to heat the tumor. The implanted tubes are removed when all treatments are complete.
Benefits of Hyperthermia
Consistent results for many decades.
Improves survival in recurrent or hard-to-treat cancers.
Virtually painless procedure.
Makes cancer cells vulnerable while preserving surrounding healthy tissue
The term LASER stands for "Light Amplification by the Stimulated Emission of Radiation." Laser light is concentrated so that it makes a very powerful and precise tool. Laser therapy uses light to treat cancer cells.
The following are some of the different types of laser used for cancer treatment: