State of the art of Mohs surgery for rare cutaneous tumors in the Spanish Registry of Mohs Surgery (REGESMOHS).

BACKGROUND: The use of Mohs micrographic surgery (MMS) for rare cutaneous tumors is poorly defined. We aim to describe the demographics, tumor presentation and topography, surgery characteristics and complications of MMS for rare cutaneous tumors in a national registry. METHODS: Prospective cohort study of patients treated with MMS in Spain between July 2013 and June 2018. The inclusion criteria were patients with cutaneous tumors with final diagnosis different from basal cell carcinoma, squamous cell carcinoma, dermatofibrosarcoma protuberans, or any kind of melanoma. RESULTS: Five thousand and ninety patients were recorded in the registry, from which only 73 tumors (1.4%) fulfilled the inclusion criteria: atypical fibroxanthoma (18), microcystic adnexal carcinoma (10), extramammary Paget's disease (7), Merkel cell carcinoma (5), dermatofibroma (4), trichilemmal carcinoma (4), desmoplastic trichoepithelioma (4), sebaceous carcinoma (3), leiomyosarcoma (2), porocarcinoma (2), angiosarcoma (2), trichoblastoma (1), superficial acral fibromyxoma (1), and others (10). No intra-surgery morbidity was registered. Postsurgery complications appeared in six patients (9%) and were considered mild. Median follow-up time was 0.9 years during which three Merkel cell carcinomas, one angiosarcoma, one microcystic adnexal carcinoma, and four others recurred (12.3%). CONCLUSION: This national registry shows that rare cutaneous tumors represent a negligible part of the total MMS performed in our country with a low complication rate.

Differences of Mohs micrographic surgery in basal cell carcinoma versus squamous cell carcinoma.

BACKGROUND: The two main tumors treated with Mohs micrographic surgery (MMS) are basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). There are no studies analyzing whether MMS is different when treating these two types of tumors. OBJECTIVE: We aim to compare the characteristics of the patients, the tumors, and MMS, and first-year follow-up of MMS in BCC and SCC. METHODS: REGESMOHS is a prospective cohort study of patients treated with MMS. The participating centers are 19 Spanish hospitals where at least one MMS is performed per week. Data on characteristics of the patients, tumors, and surgery were recorded. The follow-up was done with two visits: the first visit within 1 month after surgery and the second one within the first year. RESULTS: From July 2013 to April 2017, a total of 2,669 patients who underwent MMS were included in the registry. Of them, 2,448 (93%) were diagnosed with BCC, and 181 (7%) were diagnosed with SCC. Patients with SCC were older than those with BCC (median age 73 years vs. 68 years) and presented immunosuppression more frequently. The tumor size was significantly larger in the SCC group. Regarding surgery, deeper invasion was more frequent in SCC, resulting in larger defects. Despite this, SCC did not require more stages to get clear margins or more time in the operating room. Incomplete Mohs was more frequent in the SCC group (6%) than in the BCC group (2%). The incidence of perioperative complications was higher when treating SCC. There were more relapses in the first-year follow-up in the SCC group. CONCLUSION: There are significant differences when comparing MMS in BCC and SCC. Knowledge of these differences can help to prepare the patient and plan the surgery, optimizing results.