While the presence of a monomorphic population of immature lymphocytes on a lymph node aspirate is highly suggestive of this disease, the opinion of a pathologist with ferret experience should be sought in all cases. Alternatively, a diagnosis may be made on biopsies of visceral organs in animals with disseminated disease, with the spleen probably yielding the highest number of positive aspirates or biopsies. Over the last few years, a disturbing trend in diagnosis of this disease has been emerging - the interpretation of elevated lymphocyte counts as evidence of lymphosarcoma in the ferret. While many cases of lymphosarcoma may exhibit a lymphocytosis on the CBC, similar changes in the differential may be seen in any number of chronic smoldering infections, most notably gastric Helicobacter mustelae infection. The prudent practitioner requires a diagnosis by aspirate or surgical biopsy before any treatment is started.
Aggressive treatment appears to have a higher rate of remission than the less aggressive protocols.
In summary, practitioners who treat ferrets are certain to encounter lymphosarcoma on a regular basis. You should remember several things when such cases are presented for evaluation and treatment. The younger the ferret at presentation, the more rapid the disease progression, and the less favorable the prognosis. Young ferrets often present with signs of heart failure or respiratory disease due to the presence of a rapidly growing thymic mass. The diagnosis of lymphosarcoma is based on the presence of a monomorphic population of blastic lymphocytes on a fine needle aspirate or surgical biopsy of a lymph node or, less commonly, a visceral organ, and NOT changes seen on a complete cell count.