Retrospective Analysis of 81 Feline Lymphoma Cases Diagnosed in Surgical Biopsies in Latvia (2011-2020)

Abstract Lymphoma (also known as lymphosarcoma) is a malignant tumor accounting for 20-30% of all neoplasms in cats. There have been no previous studies summarizing trends and characteristics of feline lymphoma in Latvia. The aim of this retrospective study was to determine the prevalence and characteristics of feline lymphoma cases among biopsy submissions to a private veterinary pathology service in Latvia. Data were retrieved by selecting records from Latvian cats diagnosed with lymphoma between 2011 and 2020, including signalment, clinical history, and type of lymphoma (anatomical classification, cellular morphology). In the 10-year period, the mean prevalence of lymphoma among feline biopsy submissions was 4.8% (range 1.9 – 7.2) without upwards trend. Lymphoma was most common in mixed breed (67%), middle-aged (median 8 years) cats with a slight male predominance (56%). Among purebred cats the development of lymphomas was observed at an earlier age. The predominant anatomical type was alimentary lymphoma (53%) followed by extranodal (38%) and multicentric (7%) lymphoma. Majority of alimentary lymphomas were in the small intestine (73%) and 88% of gastrointestinal lymphomas were transmural with remaining cases limited to mucosa (12%). Overall, representation of anatomical types of lymphoma in Latvian cats was similar to those reported elsewhere; however, the subset of intestinal mucosal lymphoma in our study was underrepresented. This finding suggests that until 2021 intestinal mucosal lymphoma was uncommonly considered as a differential diagnosis for cats with enteritis therefore biopsies from such cats were not performed. This study will help Latvian veterinarians to improve diagnostic work-up of lymphoma cases.