Abstract
Background:
Lymphomas are the most common hematopoietic neoplasms in dogs and represent a heterogeneous group, as occurs in humans. Considering the role of dogs as models of human lymphomas and the geographical correlation of the cases of canine and human lymphoma, it is important to continuously assess the epidemiological distribution of lymphoma subtypes in dogs.
Aim:
The aim of this study was to provide a survey of canine lymphoma subtypes diagnosed from 2005 to 2016 in the academic veterinary pathology laboratory of the University of Porto.
Methods:
A total of 75 canine lymphomas diagnosed by histopathology in the Porto district were included. All cases were immunophenotyped by CD3 and PAX5, classified according to the current classification WHO, and coded with Vet-ICD-O-canine-1.
Results:
Mixed breed dogs were most common (28%), followed by Cocker Spaniels (12%), Boxers (9%), and Labrador Retrievers (6%). The mean age was 9.2 years (SD=3.3) (10.7 years for small, 8.9 years for medium and large, and 5.7 years for giant breed dogs, p<0.05). Regarding sex, there was no difference in frequencies nor in mean age. B-cell lymphomas were more common (57.4%) than T-cell lymphomas (37.3%), and 5.3% were classified as non-B/non-T-cell lymphomas. Of the cases, 49% had a multicentric distribution, followed by splenic (22%), cutaneous (12%), alimentary (12%), and extranodal (3%) forms. The most common B-cell subtypes were diffuse large B-cell lymphoma (DLBCL) (16.3%) and large immunoblastic lymphoma (14%), while T-zone lymphoma (21.4%) and intestinal lymphoma (18%) were the most common T-cell lymphoma subtypes.
Conclusion:
Our study shows that Porto District follows the international trend of higher prevalence of B-cell lymphomas in dogs, especially of the DLBCL subtype.

Key words: Canine, Lymphoma, Histopathology, Portugal, Vet-ICD-O-canine-1