Photo Rounds

Dark spot on back

A 44-year-old man went to see his family physician (FP) because he was concerned about a dark spot on his back that his wife said had been growing larger. He reported no symptoms related to the lesion. On physical exam, the lesion was 9 mm in diameter with asymmetry, variations in color, and an irregular border. A full-body skin exam did not demonstrate any other suspicious lesions.

What’s your diagnosis?


Dark spot on back

A biopsy revealed a compound dysplastic nevus (DN) with no signs of malignancy. There was only mild atypia (if severe atypia is reported, then the lesion often is treated as a melanoma in-situ).

The FP was initially concerned about melanoma, given the size, growth, and other characteristics of the lesion. He performed dermoscopy and noted an irregular network with multiple asymmetrically placed dots off the network. His differential diagnosis included melanoma, melanoma in-situ, and dysplastic nevus. After informed consent, he performed a saucerization (deep shave) with a DermaBlade, taking 2-mm margins of clinically normal skin, which revealed the DN. (See the Watch & Learn video on “Shave biopsy.”)

Dysplastic nevi (with mild to moderate atypia) are benign acquired melanocytic lesions of the skin. Most are compound nevi possessing a junctional and intradermal component. While dysplastic nevi are not premalignant lesions, they do have some (small) potential for malignant transformation and patients with multiple DN have an increased risk for melanoma. Cutting out all the DN does not change that risk of melanoma.

The FP explained that no further treatment was needed and offered yearly skin exams to monitor for melanoma.

Photos and text for Photo Rounds Friday courtesy of Richard P. Usatine, MD. This case was adapted from: Smith M. Epidermal nevus and nevus sebaceous. In: Usatine R, Smith M, Mayeaux EJ, et al. Color Atlas of Family Medicine. 2nd ed. New York, NY: McGraw-Hill; 2013:958-962

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