Case Report: T-Lymphoblastic Leukemia in a Dog With Erythrophagia.

A 2-year-old male German Shepherd dog was presented with progressive weight loss, lethargy, and hyporexia. Hematologic analysis revealed a moderate macrocytic normochromic anemia and moderate thrombocytopenia. Additionally, a pronounced leukocytosis was observed, characterized by 33% large lymphoid cells, marked neutrophilia with a significant left shift, and intense lymphocytosis and monocytosis. These large lymphoid cells exhibited moderately basophilic cytoplasm and nuclei with chromatin loss and occasional prominent nucleoli, along with erythrophagia and both typical and atypical mitotic figures. Serum chemistry showed mild hypoproteinemia and hypoalbuminemia. Bone marrow aspirate revealed high cellularity with lymphoid predominance and 40.6% blasts per 1000 nucleated cells, of which 2.6% showed erythrophagia. PCR for antigen receptor rearrangements performed on DNA extracted from the bone marrow smear confirmed a clonal T-cell receptor rearrangement. Despite supportive treatment and initial chemotherapy, no clinical recovery was observed, and the patient was euthanized 8 days post-diagnosis. Necropsy revealed marked splenohepatomegaly, intensely red bone marrow, mesenteric lymphadenomegaly, gastric and duodenal ulcers, and jejunal intussusception. Histologically, the bone marrow was hypercellular with monomorphic neoplastic blast cells, some exhibiting erythrophagia. Neoplastic infiltration was observed in the liver, spleen, lymph nodes, and adrenal glands. Immunohistochemistry showed blast cells positive for CD3 and negative for CD20. The final diagnosis was T-lymphoblastic leukemia with erythrophagia, underscoring the diagnostic importance of hematologic, histopathologic, and immunohistochemical evaluations in diseases with nonspecific clinical signs. Furthermore, the uncommon presentation of erythrophagia by neoplastic cells may be associated with severe anemia and poor prognosis in this patient.