Pigmented epithelioid melanocytoma - A case report.

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.

Melanoma dérmico hiperpigmentado de bajo grado de malignidad (melanoma de tipo animal): reporte de cuatro casos / Hyperpigmented dermal melanoma of low-grade of malignancy (animal-type melanoma): report of four cases

El melanoma animal o hiperpigmentado es un subtipo infrecuente de melanoma con células melanocíticas epitelioideas y fusadas muy pigmentadas. Esta entidad sería similar al llamado “melanoma de tipo equino”, una forma de melanoma de bajo grado de malignidad que afecta a los caballos grises. Se reportan cuatro casos, tres hombres y una mujer, cuyas edades variaron de 22 a 84 años; el estudio histopatológico confirmó melanoma dérmico hiperpigmentado; dos casos mostraron ganglio centinela positivo y un caso evolucionó con metástasis múltiples. Tres casos están en control o tratamiento sin evidencias de recidiva o metástasis. El melanoma animal es considerado un subtipo de melanoma de conducta poco agresiva y de mejor pronóstico, pese a su tendencia a las metástasis ganglionares. Los casos presentados mostraron una conducta menos agresiva que la esperada para el espesor de Breslow y estadio clínico en estos casos. Se requieren más estudios para poder identificar variables que permitan predecir el comportamiento biológico y así protocolizar el tratamiento de esta entidad, considerada por algunos como diferente del melanoma.

Animal type or hyperpigmented melanoma is an infrequent subtype of melanoma with heavily pigmented epithelioid and spindle melanocytes. This entity is similar to the so-called “equine-type melanoma”, an indolent variant of melanoma affecting gray horses. We report four cases, three males and one female, whose ages varied from 22 to 84 years; the histopathological study confirmed the diagnosis of hyperpigmented dermal melanoma; two cases showed positive sentinel lymph nodes and one case evolved with multiple metastases. Three cases are in control or under therapy without evidence of recurrences and/or metastases. Animal-type melanoma is considered a subtype of melanoma with indolent behavior and better prognosis, despite its tendence to develop lymph node metastases. The present cases showed a less aggressive behavior than expected for the Breslow’s thickness and clinical stage. More studies are needed to identify variables to predict its behavior and propose therapy protocols for this tumor, considered by some authors a different type of melanoma.

Melanoma de tipo animal / Animal-type melanoma

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 term‘pigmented epithelioid melanocitoma’ seems much more suitable.