Leucemia linfoblástica T em um cão: achados hematológicos, histopatológicos e imunohistoquímicos

Abstract

T-lymphoblastic leukaemia is an uncommon hematopoietic neoplasm in dogs, characterized by aggressive behavior and a poor prognosis. A 2-year-old male German Shepherd dog with a history of progressive weight loss, lethargy, and hyporexia was presented to the veterinary clinical service. A complete blood count revealed macrocytic normochromic anemia, thrombocytopenia, and extreme leukocytosis (113,200 leukocytes/µL), with 33% intermediatesized blasts and atypical mitotic figures. Additionally, neutrophilia with a left shift, lymphocytosis, and monocytosis were observed. The only abnormalities in the serum chemistry panel were hypoabuminemia and hypoproteinemia. To confirm the diagnosis of acute leukaemia, a bone marrow aspiration was performed. Myelogram revealed increased cellularity relative to fat content, with 40,6% of undifferent blasts. The PARR (PCR for Antigen Receptor Rearrangements) test was performed using the myelogram slides and showed a clonal rearrangement for T-cell receptors. The patient received symptomatic treatment, antibiotic therapy, a packed red blood cell transfusion, and prednisolone, along with a single chemotherapy session with vincristine. Following clinical deterioration, with progression to apathy and melena, euthanasia was performed eight days after the diagnosis of acute leukaemia. At necropsy, significant splenomegaly and hepatomegaly were observed, with markedly reddened bone marrow filling the entire femoral medullary cavity, enlarged mesenteric lymph nodes, small ulcers in the stomach and duodenum, and jejunal intussusception. Histopathology revealed highly cellular bone marrow with a monomorphic population of neoplastic blasts, as well as micrometastases in the liver, spleen, mesenteric lymph nodes, and adrenal glands. Bone marrow blasts showed immunoreactivity for CD3 and were negative for CD20. The combination of laboratory findings led to the final diagnosis of T-lymphoblastic leukaemia. This article discusses the hematological, histopathological, and immunohistochemical aspects of this case and highlights the importance of laboratory testing in diagnosing diseases with nonspecific clinical signs.