Tumor Characteristics, Subclinical Extent, and Time to Poor Outcomes for less Common Skin Cancers

BACKGROUND: The growth pattern and response to treatment of rare tumors are poorly understood. OBJECTIVE: To describe patient and tumor characteristics, including extent of subclinical spread and time to poor outcomes, for uncommon nonmelanoma skin cancer tumors. MATERIALS AND METHODS: PubMed and MEDLINE databases were searched for original reports of relevant tumors from January 1950 to November 2022. Review articles and reports of tumors that were previously reported or treated without margin clearance were excluded. RESULTS: Data from 347 reports were extracted. Most tumors were primary, on the head and neck, and in older individuals (except dermatofibrosarcoma protuberans). Subclinical tumor extent was greater than 3 for all types, with largest postoperative defect sizes for dermatofibrosarcoma protuberans and extramammary Paget disease. Poor outcomes occurred in greater than 20% of extramammary Paget disease and Merkel cell carcinoma cases and 10% of atypical fibroxanthoma cases. Mean times to poor outcomes ranged from 33 to 122 months, with atypical fibroxanthoma having the shortest times and sebaceous carcinoma the longest. CONCLUSION: The subclinical extent of rare tumors varies. Although disease-related mortality was rare, poor outcomes, defined to include also recurrence and metastasis, were more common. The information for time to poor outcomes may guide follow-up schedules.