Marked paraneoplastic basophilia in a cat with alimentary T-cell lymphoma

An 8-year-old, spayed female domestic shorthair cat was presented for acute weight loss, hyporexia, intermittent vomiting, and loose stools. A caudal abdominal mass and thickened intestinal loops were palpated on initial examination. An abdominal ultrasound identified a circumferential intramural jejunal mass with complete loss of wall layering, diffuse thickening of the jejunal muscularis, and jejunal and ileocecal lymphadenomegaly. Initial routine bloodwork revealed mild monocytosis and minimal lymphopenia with reactive lymphocytes. Cytologic evaluation of the jejunal mass and enlarged lymph nodes was consistent with lymphoma (intermediate cell size), and PCR for antigen receptor rearrangement revealed a clonal T-cell receptor rearrangement consistent with T-cell lymphoma. Chemotherapy (CHOP protocol) was initiated, but despite initial improvement of clinical signs, a repeat ultrasound examination 5 weeks after initiation of treatment revealed no improvement in the lymphadenomegaly or reduction in the size of the jejunal mass. At this visit, the cat also developed a marked basophilia (basophils 12.28 × 10³ /μL, RI 0.00-0.10) with low numbers of circulating atypical lymphocytes; no concurrent eosinophilia was noted. Heartworm disease, ectoparasites, and allergic diseases were evaluated for and considered unlikely. The chemotherapy protocol was changed to L-asparaginase, followed by lomustine. The basophilia was significantly reduced 2 days after the initial dose of L-asparaginase and remained within the reference interval for 40 days before an eventual decline in the cat's health. To the authors' knowledge, this is the first report of paraneoplastic basophilia without concurrent eosinophilia in a cat with T-cell lymphoma.