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Approach to the Cancer Patient
Lisa DiBernardi, DVM, DACVIM (Oncology), DACVR (Radiation Oncology)

Gulf Coast Veterinary Specialists, Houston, TX, USA

The goal of this chapter is to present an overview of tumor, plasmacytoma, transmissible venereal tumor,
current cancer terminology, patient evaluation, diagnos- lymphoma, and histiocytic tumors, but is not limited to
tic techniques, management strategies, and treatment these tumors. Leukemia results from malignant blood‐
options with emphasis on the application of radiation forming tissues of the bone marrow.
therapy. The terminology for some malignancies may be mis-
Cancer is a group of diseases that are defined by the leading. Examples include those used for lymphoma and
uninhibited growth and replication of cells. Cancer arises melanoma. Lymphosarcoma and lymphoma are terms
from an abnormal single cell that has suffered a disrup- for the same malignant process. Melanoma may be
tion in its regulatory mechanism for proliferation and benign or malignant depending on location, level of
self‐elimination. Cancer biology will be discussed in sub- invasiveness, and species. A histopathologic description
sequent chapters. will state malignant melanoma versus melanocytoma
Unregulated cellular proliferation is a characteristic of (benign melanoma).
both benign and malignant tumors. Metastasis distin- The overall mortality due to cancer in dogs is 20–30%,
guishes a malignant from a benign tumor. Metastasis is approximately one in four. The dog breed with the high-
the spread of cancer from one location to a regional or est cancer prevalence in the United States is the golden
distant location. A tumor is named based on its cell of retriever. Currently the Golden Retriever Lifetime Study
origin. A cancer that initiates from embryologically is underway in the United States. The study’s purpose is
derived endoderm, more commonly termed skin or epi- to identify the nutritional, environmental, lifestyle and
thelium of the internal organs, is a carcinoma. Carcinoma genetic risk factors for cancer and other diseases in dogs
will have a descriptor, a prefix, based on histology. An (https://www.morrisanimalfoundation.org/golden-
example of a carcinoma of the oral cavity is a squamous retriever-lifetime-study). In Sweden, a retrospective
cell carcinoma. A benign mass within skin or epithelium study found boxer and Bernese mountain dogs to be
may be an adenoma, cystadenoma or papilloma. A overrepresented in cancer deaths compared with other
malignancy of mesoderm – bone, muscle, fat, cartilage, breeds, including the golden retriever. The selection of
or other supportive structures – is termed a sarcoma. desired traits may lead to breed‐specific risks for the
Benign examples include fibroma, lipoma, hemangioma, development of cancer. Boxers, bulldogs, and retrievers
chondroma, and osteoma. Central nervous system can- are prone to cancer of the skin and subcutaneous tissues.
cers involve the brain and spinal cord and are named The Siamese cat is predisposed to the development of
after the cells lining the interior and exterior of the brain cutaneous mast cell tumors. Osteosarcoma is historically
(glial, meningeal, ependymal cells) or cells from vascular a cancer of large and giant breeds. The power to identify
structures (choroid plexus). Lymphoma (lymphosar- hereditary influences lies in the pure‐bred dog’s reduced
coma) and multiple myeloma are malignancies involving genetic complexity (diversity). Identification of pathway
immune regulatory cells. dysregulation(s) will elucidate potential upstream or
Discrete cell tumor is a term applied to tumors that downstream therapeutic targets. Current multiinstitu-
exfoliate as individual (discrete) cells, which are gener- tional consortium research is focused on the rapid iden-
ally round in shape. This category includes mast cell tification and translation of novel therapies to benefit

Clinical Small Animal Internal Medicine Volume II, First Edition. Edited by David S. Bruyette.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/bruyette/clinical