Oral Melanoacanthoma: a Case Report of Diffuse Oral Pigmentation

Abstract

Oral melanoacanthoma (OM) is an uncommon, acquired benign pigmented lesion. Normally, OM exhibits diffuse pigmentation in the oral cavity, affecting black women in the fourth decade of their life. A 53 years-old white woman, who has been a smoker for approximately 1 year, presented in an intraoral examination, brownish macules in the lower lip, gingiva, and buccal mucosa. The diagnostic hypotheses were melanin pigmentation and Addison's disease. Laboratory exams showed normal levels of ACTH and cortisol. Incisional biopsy in a region of the gingiva was performed and a microscopic exam revealed parakeratinized stratified squamous epithelium, exhibiting acanthosis and spongiosis. Numerous dendritic cells, compatible with melanocytes, distributed in the granular, prickle cell, and basal layers exhibited brownish pigments in the cytoplasm, compatible with melanin. The propria lamina consisted of dense fibrous connective tissue with mild chronic inflammatory infiltrate. Melanocytes were positive for S-100 protein. The final diagnosis was OM. All macules were removed and, after 18 months of follow-up, had no relapse of lesions.