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Lymphomas
Kristine Elaine Burgess, DVM, DACVIM (Oncology)

Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA, USA

Canine Lymphoma Epidemiology
The incidence of canine lymphoma has steadily increased,
Etiology/Pathophysiology with approximately 84 per 10 000 dogs diagnosed each

Canine lymphoma is one of the most commonly encoun­ year. Certain breeds are considered to have a higher
tered neoplasms in the dog and is most analogous to overall lifetime risk of developing lymphoma, suggesting
non‐Hodgkin lymphoma in people. It includes multiple a heritable genetic component. These include boxers,
disorders of the lymphoid system, which are character­ golden retrievers, basset hounds, and bulldogs. Likewise,
ized by a monoclonal expansion of lymphoid cells. The certain breeds of dogs are considered to be at much lower
etiology of lymphoma is currently unknown and is likely risk, including dachshunds and Pomeranians.
to be multifactorial.
Recent advances in molecular cytogenetics have dem­ Signalment
onstrated various chromosomal aberrations associated
with diagnosis and prognosis in canine lymphoma. Average age at diagnosis is between 5 and 10 years old
These results, while in the early phase of research, are with no apparent sex predilection.
similar to those seen in human non‐Hodgkin lymphoma
with dysregulation of certain molecular pathways. History and Clinical Signs

Environmental Influences Clinical presentation of multicentric lymphoma is highly
A number of case–control studies have evaluated envi­ variable and will depend on the anatomic location
ronmental influences on the development of lymphoma. and extent of the disease. An established World Health
These studies demonstrated that exposure to 2,4‐D Organization (WHO) staging scheme for domestic
herbicides increases the risk of developing lymphoma. animals assigns patients into five categories based on
Other studies have suggested that exposure to strong disease dissemination and anatomic site (Table 134.1).
magnetic fields or proximity to environmental waste This staging system is used for accurate planning of
may be risk factors. therapy, provides prognostic information, and allows
Certain viruses have been associated with the develop­ for comparisons between patients for the purposes of
ment of lymphoma in humans (e.g., Epstein–Barr virus, clinical research.
HIV). No viruses have been identified as a causative The WHO substage (a/b) is another system used
agent for the development of canine lymphoma. for prognostication and is defined as the presence/
Various immune‐mediated disorders (immune‐ absence of constitutional signs at the time of presenta­
mediated hemolytic anemia or thrombocytopenia), tion. Constitutional signs of illness include anorexia, vomit­
organ transplantation or a history of atopic dermatitis ing, diarrhea, weight loss, cachexia, fever, etc. Although
have been implicated in the development of canine these signs are somewhat subjective, this system consist­
lymphoma. ently proves to be very prognostic.

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