PATHOMORPHOLOGICAL CHANGES IN THE ORGANS OF CATS CAUSED BY ALIMENTARY LYMPHOMA. CLINICAL CASES

Abstract

The article presents the results of clinical, ultrasonographic, pathomorphological and immunohistochemical studies of two random cases of alimentary lymphoma in 9- and 12-year-old domestic cats. Clinical signs of the disease were similar and characterized by anorexia, cachexia, vomiting and diarrhea that appeared in different periods of the disease. The mucous membranes of the oral cavity and eyes were icteric, the abdomen was visually enlarged, palpation revealed nodular thickenings in the abdominal cavity. During the ultrasound diagnostics, diffuse multiple non-encapsulated anechoic formations with uneven edges and growth of tumorous tissue into the intestinal wall were visualized. In another cat, there was an encapsulated formation of a hypoechoic fine-grained structure with well-defined vascularization. From the moment of the preliminary diagnosis until the very death, the cats were kept in the clinic under supervision. After the death, an autopsy was performed with the selection of material for histopathological examination. Organs’ fragments were fixed in 10% aqueous solution of neutral formalin and Carnois fluid. Histological preparations were made according to the generally accepted methods. Immunophenotyping of lymphoma type was performed using CD3 (T-cell) and CD79a (B-cell) markers. During the pathological autopsy, an increase in mesenteric lymph nodes, their compaction, and focal thickening of the small intestine wall were revealed. The histological examination showed that jejunum was the most infiltrated intestinal segment, in which massive, diffusely placed monomorphic lymphoblastic cells were localized in the mucous membrane lamina, submucosa and muscle layers. The submucosal layer vessels were sharply dilated, filled with erythrocytes; the muscles of the inner circular layer were swollen. The outer (longitudinal) muscle layer of the jejunum thickened significantly and was intensively infiltrated by lymphoblastic cells. Typical diffuse lymphoblastic proliferations were also detected in the cortical substance of lymph nodes and lymphoid nodules. Stasis and significant expansion of the marginal sinus vessels were visualized too. In addition, moderate mononuclear lymphoblastic infiltrates were detected in the pancreas parenchyma with their perivascular location. Immunohistochemically, a significant positive expression of CD3 cells was detected both in the jejunum mucous membrane and the marginal sinus area, around the germinal centers of the lymph nodes, which indicated a T-cell type of lymphoma.