Oral Melanoacanthoma Workup

Updated: Jun 26, 2018
  • Author: Talib Najjar, DMD, MDS, PhD; Chief Editor: Jeff Burgess, DDS, MSD  more...
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Workup

Procedures

The clinical features of cutaneous and mucosal lesions may mimic those of other pigmented lesions; therefore, definitive diagnosis is based on histologic examination. Incisional or excisional biopsy may be performed based on the size and the anatomic location of the lesion. Insulinlike growth factor 2 mRNA-binding protein-3 has been suggested to help histologically differentiate keratoacanthoma from squamous cell carcinoma. [23]

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Histologic Findings

Microscopic examination reveals a hyperplastic edematous stratified squamous epithelium with acanthosis and elongated widened rete ridges. [24] Increased melanin pigmentation is present in the basal layer (see image below). In addition, many proliferating dendritic melanocytes or clear cells extend upward into the prickle-cell layers (see image below).

Increased melanin pigmentation in the basal layer Increased melanin pigmentation in the basal layer of a melanoacanthoma (hematoxylin and eosin, original magnification X10).
Proliferating dendritic melanocytes in the prickle Proliferating dendritic melanocytes in the prickle-cell layers of a melanoacanthoma (hematoxylin and eosin, original magnification X40).

The clinical and histologic features of oral melanoacanthoma lesions can resemble those of melanoma in situ. [25] Usually, no evidence of cellular pleomorphism or abnormal mitotic activity is seen in oral melanoacanthomas, and this feature excludes malignancy.

In mucosal lesions, mixed chronic inflammatory cells and numerous melanin-laden macrophages densely infiltrate the stratum corneum. This inflammatory process may indicate the reactive rather than the neoplastic nature of the lesion. [26, 27]

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