Melanoacanthoma is an extremely rare, benign, epidermal tumor characterized histologically by keratinocytes and numerous large, richly dendritic melanocytes. The majority of lesions are found on the head, neck, or upper extremities.1-3 A melanoacanthoma occurring on the lip has rarely, if ever, been reported.
Report of a Case
An 18-year-old black woman had had asymptomatic, hyperpigmented lesions on her upper lip for several months. The patient stated that her health was otherwise excellent. She denied taking any medications.Two black-brown, slightly raised, well-circumscribed plaques measuring 5 to 6 mm were present on the oral mucosa of the upper lip (Fig 1). There were no other abnormally pigmented lesions on the skin or mucous membranes.Hematoxylin-eosin sections of a biopsy specimen showed profuse numbers of dendritic melanocytes scattered throughout all levels of the acanthotic epidermis. Fontana's stain confirmed the presence of melanin within the melanocytes (Fig 2 and 3).
Matsuoka LY, Glasser S, Barsky S. Melanoacanthoma of the Lip. Arch Dermatol. 1979;115(9):1116-1117. doi:10.1001/archderm.1979.04010090058027