How are melanocytomas (nevus of Ota) and benign hamartomas differentiated from oral malignant melanoma?

Updated: Jan 31, 2020
  • Author: Elizabeth Ann Bilodeau, DMD, MD, MSEd; Chief Editor: Jeff Burgess, DDS, MSD  more...
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Melanocytomas (nevus of Ota), benign hamartomas common in the optic disc and the uveal tract in the pigmented races, are deeply pigmented and, on rare occasion, have undergone malignant transformation. These lesions have been described in cutaneous areas (scalp) and the meninges, and, when in the spinal tract, are said to have a more aggressive course. Mucosal lesions have been described in the veterinary literature.  Pigmented epithelioid melanocytoma is a melanocytic neoplasm with a Carney complex (myxomas, mucocutaneous hyperpigmentation, endocrinopathy) association. The lesion is frequently deeply pigmented and occurs on skin and mucosal surfaces. While it can metastasize to lymph nodes, the long-term prognosis is favorable. [12]

Melanotic macules (see the image below) are common on the lip, but they are also found in the oral cavity. They can be extensive in Peutz-Jeghers syndrome and are perioral or intraoral. In Addisonian pigmentation and pigmentation caused by certain medications, the etiology involves the activity of melanocyte-stimulating hormone (MSH). Bronzing associated with adrenal insufficiency is diffuse and commonly uniform. When the adrenal cortex does not respond to pituitary-released corticotropin, the continued release depletes corticotropin. A precursor protein to corticotropin and MSH is released (pro-opiomelanocortin); this protein causes the increased pigmentation.

Clinical image of an irregularly shaped, tan-brown Clinical image of an irregularly shaped, tan-brown macule on the left hard palate in an edentulous patient. The histologic diagnosis was oral melanotic macule.

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