A scoop shave biopsy was performed, including at least a 1-mm margin of normal-looking skin. Pathology was consistent with melanoma in situ.
Melanoma in situ, also called Stage 0 melanoma, is defined by atypical melanocytes that have not begun to invade the dermis and, therefore, have a Breslow thickness of 0 mm. While invasive melanoma is responsible for the largest number of skin cancer deaths in the United States (estimated to be 7990 in 2023), melanoma in situ maintains a very high cure rate when treated appropriately.1
Dermoscopy can help differentiate melanoma from benign nevi or other benign skin lesions. In this case, dermoscopy revealed a fine pigment network at the periphery that indicated this lesion was made up of melanocytes. There were also atypical vascular markings (the milky red color) in the center. Taken together, these findings were strongly indicative of melanoma.
Standard of care for melanoma in situ is a wide local excision with a margin of 5 to 10 mm. Melanoma in situ does not require sentinel lymph node biopsy. However, a lymph node biopsy would have been necessary if the melanoma had been ≥ 1 mm in thickness or if it had been ≥ 0.8 mm in thickness with higher-risk features, such as an increased number of mitoses per high-power field on pathology. Mohs micrographic surgery (MMS) is emerging as an alternative method to wide local excision to treat melanoma in situ. However, it can only be done in specialized centers that can do rapid immunohistochemical staining on frozen sections. MMS is especially useful in cosmetically sensitive areas of the body and in areas where the true size of the melanoma in situ is unclear.
This patient subsequently underwent a wide local excision in the office with a margin of 6 mm. A sentinel lymph node biopsy was not performed. The patient will continue with skin surveillance consisting of full skin exams 3 to 4 times in the first year of diagnosis, then twice annually for Years 2 to 5. He will then come in for annual skin exams after that.
Photos and text for Photo Rounds Friday courtesy of Jonathan Karnes, MD (copyright retained). Dr. Karnes is the medical director of MDFMR Dermatology Services, Augusta, ME.