Conjunctival Pigmented Epithelioid Melanocytoma: A Clinicopathological Case Report

Pigmented epithelioid melanocytoma (PEM) is a rare, melanocytic skin and mucosal tumor with low-grade malignancy. It is a recently defined histopathological entity. It encompasses epithelioid blue nevus of the Carney complex, a familial lentiginosis and multiorgan neoplasia syndrome, and most tumors previously described as animal-type melanoma (ATM).^1- 2

Dick³ first described ATM in gray horses in 1832. The similarity between the equine and human skin variant was noticed later by Darier.⁴ In 2004, Zembowicz et al¹ observed the same features in 41 ATM and 11 epithelioid blue nevus specimens and proposed the term of PEM. Because of its unique demographic characteristics, clinical presentation, histological features, and intermediate malignant potential between a benign blue nevus and common melanoma, PEM was allocated into a separate nosological category of borderline melanocytic tumors.⁵ We present, to our knowledge, the first clinicopathological case report of conjunctival PEM, initially diagnosed as ATM.