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This study involved an analysis of archived cases of canine lymphoid neoplasiafrom the University of Queensland Veterinary Pathology Laboratory from 1983 -2002. In addition, cases presented during the research period over the course of 2003were incorporated into the study. A total of 219 cases of lymphoid neoplasia were identified. These included 199 lymphomas, 18 tumours of plasma cell origin, and two acute lymphoblastic leukaemias. Through analysis of the archived signalment data for lymphoid neoplasia it was found that 46 different breeds were affected. The most commonly affected breeds were German shepherds (10.2%), boxers (6.5%), Labrador retrievers (6.0%), doberman pinschers (5.1%), and Staffordshire bull terriers (4.2%).The mean and median age of dogs with lymphoid neoplasia was 7 years and 9 months and 7 years and 10 months respectively, and the age range was 1 year and 4 months to 16 years and 10 months. The male to female ratio was 1.17:1. For canine lymphoma, the most commonly affected organs were lymph nodes (62.9% of cases), the liver(48.6% of cases), and the spleen (42.9% of cases). The multicentric form of the disease was the most frequent (45.7%), followed by the extranodal form (20.0%), the alimentary form (8.6%), and the mediastinal form (8.6%). A review of the cytological features of lymphomas in dogs found that they were morphologically diverse tumours, typically heterogeneous in appearance and with immature morphology. A review of histological specimens from cases of lymphoma in the archive found that these tumours frequently have a diffuse distribution and are composed of a population of cells exhibiting anisocytosis (mostly small to medium sized cells), and usually a low to moderate mitotic rate. Lymphomas composed of a homogenous cell population were all composed of small cells and generally had a low mitotic rate. In an immunohistochemical analysis of 35 biopsies, 4 cases had aputative B-cell phenotype and 7 had a putative T-cell phenotype.
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