In this study, the authors performed a multi-institutional retrospective evaluation of the features of tarsal lymphoma in cats. Veterinary oncologists were asked to submit cases where the samples were histologically and cytologically confirmed lymphoma with a location at or near the tarsus and described subcutaneous or mass-like.
Cutaneous lymphoma is differentiated into epitheliotropic or non-epitheliotropic forms. Most of the cases in cats are classified as having non-epitheliotropic lymphoma, though the epitheliotropic form has been reported in more recent case studies. Generally, epitheliotropic cutaneous lymphoma is considered to be a disease of T-lymphocytes, and non-epitheliotropic cutaneous lymphoma may be either T- or B-cell phenotype, with the prior reviews showing a slight predominance of T-cell over B-cell immunophenotype.
Twenty-three cats were determined to fit the diagnosis and criteria of this study. The median age was 12 years (range, 7 to 18 years). Histology revealed that most of the cases were non-epitheliotropic, of high grade, and of B-cell phenotype. No association with positive retroviral status was found. Five of the cats had confirmed popliteal lymph node involvement, with three additional cats suspected of having similar node involvement. Four other cats were suspected of lymphoma at a different site based on the results of abdominal ultrasonography. Treatments were variable and ranged from use of corticosteroids alone (2), chemotherapy (9), radiation and chemotherapy (7) or surgery with or without chemotherapy (5). Thirteen of the cats were found to have lymphoma at a different site at the time of last follow-up, death, or euthanasia. The median survival time for all the cats in this study was 190 days.
The results suggest that tarsal lymphoma in cats is an uncommon form of lymphoma in cats. Most of the cases here with cutaneous tarsal lymphoma appeared to have aggressive disease with the median survival time of 190 days, with the 1 year survival rate at 21% and 2 year rate at 4%. Systemic involvement was found --metastatic disease was found in 56% of the cats at time of follow-up or death-- therefore, thorough staging before initiating treatment is highly recommended. Future studies are needed to determine the most effective treatment protocols.
