Histopathological and immunophenotypical characterization of a combined melanoma and mucoepidermoid carcinoma in a dog

The present paper reports the fi rst case of a canine high-grade (low differentiated) mucoepidermoid carcinoma, in which malignant proliferation of melanocytes has been detected. The tumoral mass was located in the lower neck, pressing against the 7th cervical vertebral body in an aged dog of mixed breed. No macroscopic signs of skin or oral melanoma or carcinoma were detected elsewhere. The microscopic examination showed close intermingling of the two components. Melanocytic proliferation rarely occurs accompanied by the colonization of nonmelanocytic tumors, and the cause of such proliferation remains unclear. In human pathology, several reports of pigmented mucoepidermoid carcinomas have been described, and in all cases the proliferation of the melanocytic component was considered as hyperplastic, and no sign of malignant proliferation was detected. However, neither in human nor in veterinary pathology has a case of intermingled melanoma and mucoepidermoid carcinoma been described.El presente trabajo describe el primer caso de un carcinoma mucoepidermoide canino pobremente diferenciado en el que se ha observado una proliferación maligna de melanocitos. La masa tumoral se localizó a nivel del 7º cuerpo vertebral en perro de raza mestiza. No se detectaron otros signos macroscópicos de carcinoma y/o melanoma oral o epitelial. El examen microscópico reveló la proliferación conjunta de ambas subpoblaciones. La proliferación y colonización de melanocitos en tumores de origen no melánico es rara y no se conoce la causa. En Patología humana, se han descrito casos de carcinomas mucoepidermoides pigmentados, pero en todos los casos se consideró la proliferación melanocítica como hiperplasia, no observándose en ningún caso signos de neoplasia. No existen en Patología humana ni veterinaria ningún caso descrito de carcinoma mucoepidermoide concomitante con un melanoma maligno, siendo éste el primer caso descrito