RESUMEN
Pigmented epithelioid melanocytoma (PEM) is a borderline melanocytic neoplasms or a low-grade melanoma which is rare. It affects all age groups. The prognosis is relatively good compared to conventional malignant melanoma. We presented here a case of 3 years old Saudi girl presented with an asymptomatic brown-black lesion on her left forearm. At clinical examination,the lesion had a diameter of 0.6 cm, appeared round, exophytic, and intensely pigmented with well-defined edges and bluish reflections. All features strongly suggested nodular melanoma and the lesion was excised and histopathology showed asymmetrical growth of heavily pigmented atypical epithelioid and spindle cells. A pigmented epithelioid melanocytoma, so-called animal-type melanoma, was diagnosed. The depth of invasion was classified as Clark level IV, with maximum thickness of 3 mm.
RESUMEN
Lo que se ha dado en llamar melanoma de tipo animal es un tumor aún no bien determinado ni clasificado. Tiene similitudes clínicas e histopatológicas con el melanoma que se observa en los caballos de pelaje tordillo: un infiltrado alarmante, denso y extenso, de células que ocupan toda la dermis y aún el celular subcutáneo, acompañado sin embargo de un pronóstico benigno y larga sobrevida. El nombre propuesto por Zembowicz et ál., melanocitoma epitelioide pigmentado, parece más adecuado para esta rara variante de melanoma.
Animal-type melanoma is a rare distinct variant of melanoma, charac-terized by a dense proliferation of epithelioid and spindle-shaped mela-nocytes occupying the dermis and the hypodermis, and resembles theheavily pigmented melanomas as seen in grey horses. Only a limitednumber of cases have been reported and, as such, the clinical character-istics of this melanoma variant are incompletely understood. Despite thehigh mean thickness of the tumors, reports indicate a less aggressive behavior and a better outcome of this tumor when compared with conven-tional melanoma, but the underlying pathways related to this particularoutcome are still unknown. As proposed by Zembowicz et ál., the termpigmented epithelioid melanocitoma seems much more suitable.