An epidemiological study of canine lymphoma in South Africa.

Breed, age, and sex predispositions for canine lymphoma have been reported for various geographical locations. However, epidemiological information concerning canine lymphoma in South Africa is scarce. The aim of the study was to describe the epidemiological features of canine lymphoma and the frequency of World Health Organization (WHO) classification subtypes in South Africa. A retrospective, case-control study was performed that included 342 cases with a histopathological diagnosis of canine lymphoma matched with 342 canine non-lymphoma control cases. Associations between canine lymphoma and breed, age, sex, and neutering status were assessed using univariate and multivariable conditional logistic regression. Associations were reported as odds ratios and significance set as <i>p</i>≤ 0.05. Breed was significantly associated with canine lymphoma, but not age, sex, or neutering status. Median population age was eight years, with a male-to-female ratio of 1.2:1. The Boerboel had an increased risk (OR = 1.63, CI = 1.02-2.62, <i>p</i> = 0.002) and the Yorkshire Terrier a decreased risk (OR = 0.59, CI = 0.38-0.93, <i>p</i> = 0.050) of having canine lymphoma. Immunophenotyping was performed on 119 (35%) cases, of which 82 (69%) were B-cell, 34 (29%) T-cell and three (2%) neither. WHO subtype was available for 88 cases; of these 66 (75%) were diffuse large B-cell lymphoma (DLBCL) with remaining subtypes each ≤ 7%. This study identified a breed predisposition for canine lymphoma in the Boerboel, a South African mastiff-type dog, but significant associations were not detected for age, sex, and other breeds. The frequency of immunophenotypes and WHO subtypes was similar to previous studies in other locations.