Excerpt from Cutaneous Melanoacanthoma

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Background

Melanoacanthoma is a term that Mishima and Pinkus¹ introduced in 1960 to describe a pigmented, benign proliferation of both keratinocytes and dendritic melanocytes. Prior to this designation, Bloch² described a similar lesion in 1927 that he called melanoepithelioma type I. Melanoepithelioma type II is an ordinary pigmented seborrheic keratosis.

Oral melanoacanthoma is a rare, reactive, mucosal lesion, which, similar to cutaneous melanoacanthoma, is associated with hyperplasia of spinous keratinocytes and melanocytes.³ Its most common intraoral sites are the buccal mucosa, lip, palate, and gingiva. The average age at presentation is 28 years, and it occurs mainly in blacks, with a strong female predilection.⁴ Oral melanoacanthoma is unrelated to seborrheic keratosis. Oral melanoacanthoma is most often seen as an enlarging flat or slightly raised area of hyperpigmentation on the buccal mucosa of adult black women. Strong homatropine methylbromide reactivity has been described, limiting its utility in distinguishing oral melanoacanthoma from malignant melanoma.

The eMedicine article Oral Melanoacanthoma may be of interest, as may the Medscape Dermatologic Surgery Resource Center.

Pathophysiology

Although melanoacanthoma can be found both on the skin and oral mucosa, the focus of this review is cutaneous melanoacanthoma. Although most authors consider cutaneous melanoacanthoma a benign tumor of melanocytes and keratinocytes, some have suggested it may be a reactive phenomenon induced by localized trauma.⁵

Frequency

United States

Cutaneous melanoacanthoma is generally regarded as rare. It was the primary diagnosis in 5 of 500,000 consecutive skin biopsy samples in one series from the United States.⁶

International

In their series of 189 consecutive seborrheic keratoses diagnosed among Spanish patients, Simon et al⁷ found that cutaneous melanoacanthoma represented 28% of all seborrheic keratoses.

Mortality/Morbidity

• Cutaneous melanoacanthoma is a benign neoplasm. Simple excision is curative.
• Morbidity is uncommon. However, a melanoacanthoma that extends from the upper eyelid to beyond the lower eyelid can obstruct the patient's vision. The authors have observed this complication.
• Melanoacanthomas may be as large as 10 cm in diameter and can therefore be unappealing to the patient.

Race

Cutaneous melanoacanthoma is described more frequently white patients than in others. However, the lesion is rare in all ethnic groups.

Sex

Cutaneous melanoacanthoma develops in males and females with the same frequency.

Age

Cutaneous melanoacanthoma develops in middle-aged and elderly people. Melanoacanthoma has been described in patients aged 46-81 years, with an average age of 55-65 years.^{6, 8}

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