B-CELL ACUTE LYMPHOBLASTIC LEUKEMIA IN A YOUNG DOG: HEMATOLOGICAL, ANATOMOPATHOLOGICAL AND IMMUNOHISTOCHEMICAL ASPECTS

Abstract

B-cell acute lymphoblastic leukemia (B-ALL) is a hematopoietic neoplasm characterized by the rapid proliferation of immature cells in the bone marrow, resulting in impaired hematopoiesis and infiltration of extramedullary organs. This study aimed to report a case of B-ALL in a 10-month-old male Pit Bull dog. The diagnosis was established based on clinical, hematological, myelographic, and immunohistochemical findings. The patient presented lethargy, hyporexia, weight loss, and pale mucous membranes. Hematological evaluation revealed anemia, thrombocytopenia, progressive leukocytosis, and circulating lymphoblasts, with an increase in the proportion of blasts from 34% to 89% over 11 days. The myelogram revealed bone marrow hypercellularity, with 60.2% blasts. Due to the rapid progression and unfavorable prognosis, euthanasia was elected, followed by a post-mortem examination. Necropsy and histopathology revealed neoplastic infiltration in the liver, spleen, kidneys, and central nervous system. Immunohistochemistry showed immunoreactivity for PAX5 and CD20 and a Ki-67 proliferative index of 60%, supporting the diagnosis of B-ALL. The case highlights the rarity of B-ALL in young dogs and the importance of an integrated diagnostic approach for the characterization of this neoplasm.