Bcl-2 Immunoexpression in Feline Epitheliotropic Intestinal T-Cell Lymphomas

Abstract

Lymphoma is the most common malignant hematopoietic neoplasm in domestic felines. Twenty-two cases of feline epitheliotropic duodenal T-cell lymphoma were characterized morpho-logically and immunohistochemically (CD3, Pax5, Ki-67), and Bcl-2 immunoexpression was estab-lished. Most cases were in domestic shorthair cats (88.2%), with a mean age of 11.2 years. All lymphomas were CD3+, with a low-to-moderate expression of Ki-67 (< 30%). A correlation between the tumoral pattern of infiltration in the lamina propria and the intraepithelial distribution of the neo-plastic lymphocytes was established (p = 0.0155). Intraepithelial nests of neoplastic lymphocytes were predominantly observed in lymphomas with a patchy distribution in the lamina propria, whereas intraepithelial plaques were seen in lymphomas with an obliteration pattern. Bcl-2 was expressed in neoplastic cells in all cases, and a higher expression was associated with increased villous stunting (p = 0.0221), and tended to be present in those cases with increased epithelial dam-age. The expression of Bcl-2 and the degree of epitheliotropism were correlated with neoplastic progression in epitheliotropic intestinal T-cell lymphomas; those displaying high Bcl-2 immunoex-pression showed increased villous stunting and epithelial damage, suggesting that Bcl-2 is overex-pressed in advanced tumor stages, and may be used as a predictor of tumoral behavior in feline epitheliotropic intestinal T-cell lymphomas. This entity showed many similarities with human MEITL, so the latter entity should be considered in further lymphoma classifications of domestic animals.