Abstract
Canine lymphoma is a hematopoietic neoplasm that can affect different tissues. Its classification is performed according to cellular morphology, clinical stage, immunophenotyping, and anatomical location. However, in some cases, an oncopathy might be in an advanced stage with a plain organic spread, making it impossible to determine the initially affected tissue, which is a rare situation in animals. Thus, a case of metastatic lymphoma, of unknown primary origin, was described in a four-year-old Rottweiler bitch with multiple nodular subcutaneous proliferations. Hematological, biochemical, thoracic radiography, and abdominal ultrasound tests were performed, as well as a cytopathological examination of subcutaneous lesions and bone marrow. Hematologic findings determined anemia, lymphopenia, and thrombocytopenia. The thoracic radiography revealed multiple nodular masses. Cytopathological examination revealed infiltration of malignant lymphocytes into the subcutaneous nodules and into the bone marrow. The dog was euthanized and submitted to necroscopic examination, in which multiple nodules were found in the subcutaneous region, lung, pericardium, gastrointestinal tract and in the skeletal musculature, in addition to lymphadenopathy. Fragments of the affected structures were collected for later histopathological and immunohistochemical evaluation. Histopathological examination revealed the presence of neoplastic cells compatible with diffuse lymphoma, which was positively immunolabelled for T-cell lymphoma. Based on clinical-pathological findings and other complementary tests, a diagnosis of diffuse T-cell lymphoma of unknown primary origin was made. In order to classify hematopoietic neoplasms, it is essential to perform different laboratory tests. However, determination of origin becomes difficult when such an oncological disease presents an advanced stage.
Highlights
Canine lymphoma is a hematopoietic neoplasm, characterized by the clonal proliferation of malignant lymphocytes, originating mainly in lymphoid organs, different tissues of the organism may be affected (RODRIGUES et al, 2016; ZANDVLIET, 2016)
Histopathological examination revealed the presence of neoplastic cells compatible with diffuse lymphoma, which was positively immunolabelled for T-cell lymphoma
The primary anatomical identification of the lymphoma is obtained through the association of clinical signs with the findings of the cytological and/or histopathological examination of the compromised tissue (ZANDVLIET, 2016)
Summary
Canine lymphoma is a hematopoietic neoplasm, characterized by the clonal proliferation of malignant lymphocytes, originating mainly in lymphoid organs, different tissues of the organism may be affected (RODRIGUES et al, 2016; ZANDVLIET, 2016). A: Subcutaneous proliferation exhibiting neoplastic lymphocytes (yellow arrows), with anisocytosis, anisokaryosis, and nucleoli sometimes difficult to distinguish, the cytoplasm is sparse and basophilic (40x objective, rapid Romanowsky stain). A neoplastic proliferation was observed and characterized by the presence of coalescing foci of round cells, which are characteristic of small and medium lymphocytes with evident nucleoli, randomly distributed in the nucleus. They presented marked anisocytosis and cellular atypia, and high mitotic index. A: Proliferation presenting neoplastic round cells (yellow circles), with lymphocyte characteristics, presenting anisokaryosis, nuclear atypia and evident nucleoli (40x objective, staining: Hematoxylin and Eosin).
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