Feline leukemia virus-negative acute lymphoid B-cell aleukemic leukemia in a cat with prolonged survival.

A 13-year-old feline leukemia virus-negative cat was diagnosed with acute lymphoid B-cell aleukemic leukemia. The diagnosis was based on the combination of pancytopenia, large and atypical round cells present on liver and splenic cytology, bone marrow cytology and histopathology showing a majority nucleated population of atypical blast cells, immunohistochemistry, and a lack of malignant lymphoblasts observed in the peripheral blood. The cat was initially treated with L-asparaginase, vincristine, doxorubicin, cyclophosphamide, and prednisolone, which led to a resolution of the cytopenias. After relapse on Day 242, lomustine was first administered, followed by a modified protocol of vincristine, mitoxantrone, cyclophosphamide, and prednisolone, due to progressive disease. A survival time exceeding 1 y following diagnosis was obtained. This case highlights both a rare, aleukemic form of acute lymphoid leukemia in a feline leukemia virus-negative cat and an atypically prolonged survival time. Key clinical message: Prolonged survival of cats with acute lymphoid aleukemic leukemia is possible with chemotherapy treatment.