Cutaneous Melanoacanthoma

Melanoacanthoma is a rare, benign cutaneous neoplasm. The lesion is more common in older adults, with a median age of 65 and a male predominance. Cutaneous melanoacanthoma has an unclear etiology, though some argue the presentation is a heavily pigmented seborrheic keratosis variant. The initial presentation is typically a solitary, slow-growing black nodule on the head, neck, trunk, or extremities (see Cutaneous Melanoacanthoma on the Right Preauricular Cheek). Clinical examination, dermoscopy, and reflectance confocal microscopy of melanoacanthoma may be equivocal compared with malignant disease, so a biopsy with histopathologic evaluation is essential. Microscopic examination shows an epithelial lesion with hyperkeratosis, acanthosis, and papillomatosis. The epidermis has mixed melanocytes with large dendritic processes and keratinocytes. Further staining with Fontana-Masson, S100 protein, or Melan-A (ie, MART-1) may be required to pinpoint a diagnosis. Conservative excision of cutaneous melanoacanthoma is the treatment of choice since incomplete removal of the tumor can result in persistence and continued growth or recurrence of the lesion. Follow-up for patients with cutaneous melanoacanthoma should include evaluating any new or recurring lesions.  Melanoacanthoma, called oral melanoacanthoma, may be present in the mouth (or other mucosal epithelium) and is thought to be reactive without tumor-like progression. See the StatPearls companion resource, "Oral Melanoacanthoma," for more information. In contrast, the neoplasm can also occur on non-mucosal sites as a benign neoplasm and is designated as a cutaneous melanoacanthoma. Considerable debate exists if pigmented seborrheic keratosis and cutaneous melanoacanthoma are 2 distinct entities, but they are considered separate, given their unique clinical features and management. Melanoacanthoma is associated with other syndromes. Metachronous oral melanoacanthomas were found in patients with Laugier-Hunziker syndrome, and melanoacanthoma on the lower lip has been associated with plasma cell cheilitis and Langerhans cell hyperplasia of the lower lip.