Cytomorphological and immunological classification of feline lymphomas: clinicopathological features of 76 cases.

Of the various classification systems for non-Hodgkin's lymphoma, the updated Kiel classification is valuable for veterinary practice, because of its utility to classify the subtypes not only by histopathology but also by cytomorphology. However, there are only a few reports of small number of feline lymphomas to apply the updated Kiel classification. In this study, immunogical subtypes and morphology of 76 feline lymphomas were evaluated and classified into subtypes of the updated Kiel classification. Of the cases, 49% were T-cell lymphoma, 25% were B-cell lymphoma and 26% were undetermined immunological subtype. Based on the updated Kiel classification, most subtypes were identified also in feline lymphomas as in dogs and humans. Globule leukocyte lymphoma was specific for cats and relatively common in feline alimentary lymphomas. Of the present cases, 64% were high-grade subtypes, whereas 36% were low-grade subtypes. The present study indicated that feline lymphomas could be morphologically classified by the modified updated Kiel classification.