Oral Melanoacanthoma: A Report of Two Cases and a Review of the Literature

Oral melanoacanthoma (MA) is a rare, benign pigmented lesion that presents as a painless, rapidly growing, brown-black macular lesion that commonly affects the buccal mucosa in areas that are subject to chronic trauma/irritation.^1,2 MA is commonly seen in the third and fourth decades of life and primarily affects blacks with a strong female predilection.^3,4 Histopathologically, the lesions exhibit proliferation of keratinocytes and dendritic melanocytes.⁵ This report includes two cases of oral melanoacanthoma and a review of the literature.

Case 1: A 43-year-old black female presented with a slowly enlarging pigmented lesion on the right buccal mucosa. The patient did not recall any known trauma to the area or previous infection and reported that the lesion was painless but had a gradually increased in size. Oral examination revealed a 2.0 x 2.0 cm. brown macule on the right buccal mucosa. A punch biopsy was taken of the pigmented area. The tissue was placed in 10% formalin and submitted for microscopic examination. The tissue was stained with hematoxylin and eosin and exhibited acanthotic, stratified squamous epithelium with dendritic melanocytes dispersed throughout the epithelium consistent with a diagnosis of melanoacanthoma.

Case 2: A-35 year-old black female presented with a rapidly growing pigmented lesion on the left buccal mucosa. Two years prior to presentation the patient had noted a brown lesion on the buccal mucosa adjacent to a fractured tooth. The lesion remained unchanged and asymptomatic for approximately two years. One week prior to presentation, the patient noted that the lesion was enlarging, but remained painless. Oral examination revealed a 1.5 x 1.5 cm. brown macule surrounded by erythema on the left buccal mucosa adjacent to a fractured tooth. A punch biopsy was taken that included both the pigmented and erythematous areas. The tissue was placed in 10% formalin and submitted for microscopic examination. The tissue was stained with hematoxylin and eosin and exhibited similar histopathologic features to the previous case. Immunohistochemical staining with S-100 and Melan-A dramatically demonstrated the dendritic melanocytes.

Review of the literature revealed a total of 50 cases of oral melanoacanthoma. These lesions were reported in black females on the buccal mucosa with subsequent resolution. The cases here demonstrate similar clinical features and age at presentation to previously reported cases. The pathogenesis of oral MA remains unclear, however, most studies suggest this is a reactive process due to chronic irritation.² Oral MA may regress following biopsy and no surgical intervention is required due to its self-resolving quality.⁵

References:

1. Chandler K, Chaudhry Z, Kumar N, Barrett A, Porter S. Mela- noacanthoma: A rare cause of oral pigmentation. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 84:492-4, 1997
2. Fatahzadeh M, Sirois DA. Multiple intraoral melanoacanthomas: a case report with unusual findings. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 94(1):54, 2002
3. Fornatora ML, Reich RF, Haber S, Solomon F, Freedman PD: Oral melanoacanthoma – a report of 10 cases, review of the liter- ature, and immunohistochemical analysis for HMB-45 reac- tivity. Am J Dermatopathol 25:12-15, 2003
4. Kauzman A, Pavone M, Blanas N, Bradley G: Pigmented lesions of the oral cavity: Review, differential diagnosis and case presentations. J Can Dent Assoc 70:682-683, 2004
5. Neville BW, Damm DD, Allen CM, Chi AC: Oral and Maxillofacial Pathology, ed 4, Elsevier, Inc.