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The pathology report confirmed the benign nature of this congenital melanocytic nevus (CMN). CMNs are hamartomatous lesions that form when collections of melanocytes (normal pigment cells) congregate in one location. These cells migrate during the embryonal stage of development—but some never make it to their final destination.

While CMNs are almost always benign, the history of change in this case made excision compelling. Given the lesion’s likely extension well under the surface of the skin, a shave removal would not suffice—and would leave a noticeable scar.

Despite their low potential for malignancy, CMNs—like any lesion removed from the body—must be sent for pathologic examination. The general rule is: the larger the congenital lesion, the greater the malignant potential.

Remember, too, that not all skin cancers are melanomas. Virtually any cell in the skin (sweat glands, neural tissue, sebaceous glands, smooth muscle, and even hair follicles) can undergo malignant transformation, so microscopic examination is mandatory for all removed lesions, except tiny tags or warts.

Interestingly, CMNs are more common on patients with lighter skin. However, besides the case patient, there were also several family members reporting a history of similar lesions. They were all thrilled with the patient’s cosmetic outcome—and more so with the benign report.


  • Congenital melanocytic nevi (CMNs) are collections of melanocytes in one area.
  • CMNs have little malignant potential, but morphology (eg, color, shape, symptoms) or size may dictate the need for removal or biopsy.
  • Deep shave or excision are the best options for removal; patient age, lesion location, potential for scarring, and surgical ability of the provider influence choice.
  • Since melanocytes can end up in other extracutaneous locations, primary melanomas can develop almost anywhere—including the lungs, the gut, or even the eyes.

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