Anaplasic melanoma in equine of hair tissue with metastase in bone and muscle

Abstract

Melanomas are cutaneous neoplasms, originating in melanocytes. These neoplasms are referred to as melanocytic lesions, and are classified as melanocytic nevus, anaplastic melanoma and dermal melanoma. In equines, they are more frequent in animals of tordilha coat. The objective of this study was to report a case of anaplastic melanoma in a tordilha fur horse referred to the Regional Diagnostic Laboratory of the Veterinary School of the Federal University of Pelotas. In the external examination of the cadaver, blackened, solid masses, multilobulated in the ventral region of the tail, perineum and upper lip were observed. At necropsy, there were masses with the same characteristics in lymph nodes, muscles of the hind limbs and in the condyle of the occipital bone. Histologically it was observed in all tissues, proliferation of cells with rounded nuclei, and abundant cytoplasm, containing large amount of melanin granules. Mitoses were frequent and there was marked cellular pleomorphism. Based on macroscopic and microscopic findings, anaplastic melanoma was diagnosed.