Mucinous nevus with fat: an unusual case report and literature review.

Mucinous nevus is a rare entity classified as either cutaneous mucinosis or connective tissue nevi. Clinically, multiple papules or plaques develop at birth or in early adulthood and grow to form verrucous or nevoid feature with a unilateral or often zosteriform distribution on the trunk. Histopathologically, it is characterized by mucin deposits localized in the papillary dermis, clearly distinguishing this entity from other types of cutaneous mucinosis. A 18-year-old male presented with multiple, skin-colored, pinhead to pea-sized, grouped, flat tapped, soft papules on the back. This skin lesion was found accidentally 3 years ago with no symptom. Histologic findings revealed an acanthotic epidermis with thin elongated rete ridges and orthohyperkeratosis. In papillary dermis, fine collagen fibers were interspersed in an abundant ground substance that stained positively with Alcian blue at pH2.5. Herein the authors describe an unusual case of mucinous nevus and review the relevant literature.