ONCOLOGY TERMINOLOGY
BENIGN VERSUS MALIGNANT
"Tumors that normally do not destroy their host or are, at worst, capable of causing the destruction of the host from a purely position-functional standpoint, are known as benign tumors. Malignant tumors consist of cells that are intrinsically dangerous because they are rapidly growing and quickly cause cachexia or they invade and metastasize."
"In theory, there is no one single criterion that defines malignancy. Invasion or metastasis is characteristic of malignancy, which is best defined by microscopic examination of tissue. The microscopic characteristics used by the pathologist to make a diagnosis of malignancy are collectively known as anaplasia. An anaplastic or undifferentiated malignant tumor is made up of cells that lack many of the overt features of the original differentiation. From a practical standpoint, evidence of invasion or metastasis in an adult animal is diagnostic of malignancy."
NAMING OF TUMORS BY ANATOMIC SITE AND DEGREE OF ANAPLASIA
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BENIGN
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MALIGNANT
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| EPITHELIAL | -polyp or adenoma | EPITHELIAL | -carcinoma |
| NON-EPITHELIAL | tissue + oma | NON-EPITHELIAL | tissue + sarcoma |
Examples: A benign tumor of fat is a lipoma. A malignant tumor of the outermost layer of the skin is a squamous cell carcinoma.
Exceptions / Clarifications: The prefix -adeno means gland. Benign tumors of glandular tissues are adenomas. Malignant tumors of glandular tissue are adenocarcinomas. Melanoma is malignant and really should be called melanocarcinoma. Similarly, myeloma really should be myelosarcoma. Other such examples exist (lymphoma, leukemia). The value of differentiating carcinomas (crab-like tumors) from sarcomas (fleshy tumors) is that carcinomas tend to spread via the lymphatics while sarcomas tend to spread via the vasculature.
Taken from Pierce GB, Shikes R, Fink LM. Cancer: A problem of developmental biology, Prentice-Hall, Englewood Cliffs NJ, 1978 - this book is an oldie but a goodie!