Canine cutaneous lymphoma of large granular lymphocytes non-B, non-T natural killer immunophenotype with cardiac, gastric and hepatic involvement.

Cases of natural killer (NK)-cell large granular lymphocyte lymphoma are extremely rare, accounting for approximately 0.8% to 2.56% of lymphomas in dogs. A 5-year-old male Rottweiler presented with multiple cutaneous nodules and progressive weight loss, with a clinical course of less than 2 months. Following inconclusive cytology, an incisional biopsy was performed for histopathological and immunohistochemical analyses. Histopathological examination revealed a neoplastic proliferation of round cells infiltrating the deep dermis and subcutaneous tissue. The microscopic features, combined with the immunostaining profile-negative for CD3 and CD79a and positive for CD18 and granzyme-indicated a diagnosis of large granular lymphocyte lymphoma with a non-B/non-T immunophenotype of NK-cell origin. The patient underwent chemotherapy with lomustine and completed three treatment sessions before being euthanized, with a survival time of 93 days. Necropsy revealed involvement of the lymph nodes, heart, stomach, liver, and skin. Histopathological and immunohistochemical findings confirmed the antemortem diagnosis at all sites. To the best of our knowledge, this is the first report of cutaneous, cardiac, gastric, and hepatic involvement associated with non-B, non-T large granular lymphocyte lymphoma in dogs.