An epidemiological study of canine lymphoma in South Africa

Abstract

Breed, age, and sex predispositions for canine lymphoma (cL) have been reported for various locations. However, epidemiological information concerning cL in South Africa is scarce. The objective of the study was to describe the epidemiologic and histological features of cL and the frequency of World Health Organisation (WHO) classification subtypes in South Africa. A retrospective case-controlled study was performed that included 342 cases, submitted between December 2018 – December 2020, with a histopathological diagnosis of cL, matched with non-cL control cases. Associations between cL and breed, sex and age were assessed using univariate and multivariable conditional logistic regression. Associations were reported as odds ratios (ORs) and significance set as P ≤ 0.05. Breed, in general, was significantly associated with cL, but age, sex, and neutering status were not. Median population age was 8 years, with a male to female ratio of 1.2:1. The Boerboel had an increased (OR = 3.25, P = 0.004) and the Yorkshire Terrier a decreased risk (OR = 0.17, P = 0.004) of developing cL. The Boerboel cL group (n = 27) had a younger median age of 6 years and a higher male to female ratio of 1.5:1. Immunophenotyping was performed on 119 (35%) cases, of which 82 (69%) were B-cell, 34 (29%) T-cell and 3 (2%) neither. World Health Organisation classification subtypes were available for 88 cases; of these 66 (75%) were diffuse large B-cell lymphoma (DLBCL) with remaining subtypes each ≤7%. All Boerboel cases (n =4) that were WHO subtyped were DLBCL. This study confirmed a breed predisposition for cL in the Boerboel, a South African mastiff-type dog, as previously reported. However, the lack of association between age, sex, and other breeds, and cL, was unexpected. The frequency of immunophenotypes and WHO classification subtypes were largely similar to findings in other locations. The study results suggest a possible predilection for B-cell lymphoma in the Boerboel.