Melanoma subtleties

National report - The presence of background atypical junctional melanocytic hyperplasia may sometimes make it difficult for the Mohs surgeon to assess clear and exact margins during Mohs micrographic surgery for melanoma in situ arising on the sun-damaged skin of the head and neck.

It is crucial for the Mohs surgeon to be able to distinguish the subtle features of melanoma in situ from melanocytic hyperplasia arising on sun-damaged skin. Authors James O. Barlow, M.D., in private practice in Peoria, Ariz., John C. Maize Sr., M.D., in private practice in Charleston, S.C. and Pearon G. Lang, Jr., M.D., of the Medical University of South Carolina studied and further dissected the intricate differences of the density and distribution patterns of melanocytes adjacent to melanoma and non-melanoma skin cancers. They were attempting to elucidate the similar and sometimes parallel histological picture seen in skin cancers and sun damaged skin, ultimately assisting the Mohs surgeon in being more precise in tumor extirpation.

The research was conducted at the Medical University of South Carolina, and Dr. Barlow presented the findings at the American College of Mohs Micrographic Surgery and Cutaneous Oncology meeting.

"We found there is a significantly increased density of melanocytes adjacent to melanomas compared to basal and squamous cell carcinomas (BCC and SCC), corroborating previous observations of melanocytic hyperplasia surrounding melanomas."

Study configuration

All samples were stained with H&E and sectioned vertically with a thickness of 6 microns.

The Fitzpatrick skin type of the patients included type I (16.7 percent), type II (50 percent) and type III (33.3 percent).

All of the original primary tumors had clear margins. Dr. Barlow says that there were higher melanocyte densities (per 1 mm of epidermis) in the skin specimens adjacent to the melanomas (p<0.001), and that this was consistent with previous observations of melanocyte hyperplasia surrounding melanomas. Contiguous melanocytes were the most common architectural feature seen among the skin biopsies (17.1 percent of patients), and it was more commonly seen in those specimens that also had a higher melanocyte density (p<0.001). No more than four contiguous melanocytes were encountered in these samples.

Atypical melanocytes were seen in 4.6 percent of patients. This was more commonly seen in those specimens that demonstrated a higher melanocyte density (p<0.001). Also, no mitotic figures were encountered in these specimens. Follicular extension of melanocytes was observed in 6.3 percent of the patients, and again, this was more commonly seen in the skin specimens with higher melanocyte density (p<0.001).

Nested and pagetoid melanocytes were also noted, but were rare. Dr. Barlow notes that because of this rarity, a nested or pagetoid melanocyte or pagetoid melanocytes should raise one's suspicion for melanoma in situ.

"Because some of the features of melanoma in situ can be seen adjacent to non-melanoma skin cancers in sun-damaged skin, use caution when applying conventional criteria for the diagnosis of melanoma in situ on sun-damaged skin." Dr. Barlow says.