Animal-type melanoma: report of five cases with sentinel node biopsy and fluorescence in-situ hybridization analysis.

Animal-type melanoma (ATM) is a rare tumor, characterized histologically by a predominantly dermal proliferation of heavily pigmented epithelioid and spindle dendritic melanocytes. Five patients with ATM, who had undergone sentinel node biopsy, were studied: three male and two female, between 4 and 62 years of age (mean, 28.0). Lesion size ranged from 4 to 18 mm and thickness from 0.7 to 5.1 mm. Nodal deposits were found in three patients. Of the patients with positive sentinel nodes, the first showed a minimal nodal involvement in one node, the second multiple deposits in one node, and the third multiple deposits in one sentinel node and a single deposit in another; this last patient also had additional tumor deposits in a nonsentinel regional node. Fluorescence in-situ hybridization tumor analysis proved negative in all cases. All patients are alive and free of disease at 36-95-month follow-up (mean, 53 months). Results showed ATM as a neoplasm characterized by a somewhat high rate of lymph node involvement but relatively low rate of visceral metastases and mortality, appearing as a low-grade malignant tumor.