Immunophenotypic characterization of lymphocytic infiltration in canine melanocytic tumors / Caracterização imunofenotípica da infiltração linfocítica em tumores melanocíticos caninos

Abstract

Melanocytic tumors correspond to approximately for 4 to 7% of tumors in dogs and up to 7% of malignant tumours. Melanomas generally exhibit aggressive biological behavior. In humans, abundant tumor-infiltrating lymphocytes (TIL) can be considered a good prognostic factor. Research on TIL in canine melanomas is scarce, and to date, there are no studies to verify its association with established prognostic factors. Our study aimed to evaluate the lymphocyte population in canine melanocytic tumors using immunohistochemical markers, and to relate this to pre-established clinicopathological prognostic variables and cell proliferation index (Ki-67). An exploratory cross-sectional study was conducted with 21 cases in 19 dogs, of which 71.5% were melanotic melanomas, 19% were melanocytomas and 9.5% were amelanotic melanomas. Ki-67 expression was elevated in amelanotic melanomas, indicating aggressive tumor behavior. We detected lymphocytes T and B through CD3 and CD20 markers, respectively, and found that 86.7% of the melanotic melanomas were positive for CD3, whereas 73.3% were negative for CD20. TIL showed a strong association with malignant tumors, as well as a correlation with other pre-established prognostic factors, such as necrosis, ulceration, and nuclear atypia. TIL need to be further investigated to verify its inclusion as a prognostic factor for canine melanomas