Basosquamous carcinoma and metatypical basal cell carcinoma: a review of treatment with Mohs micrographic surgery

Abstract

Basosquamous carcinoma (BSC) and metatypical basal cell carcinoma (MBCC) are uncommon tumors poorly defined in the literature. Available studies suggest these tumors carry a greater risk of recurrence and metastases than basal cell carcinomas (BCCs) and, in some studies, squamous cell carcinomas. Formal treatment recommendations are not fully established. To analyze BSC and MBCC separately, evaluate whether they are distinct tumor subtypes, and analyze Mohs micrographic surgery (MMS) efficacy for BSC and MBCC. Retrospective review of medical records and histologic specimens was conducted for 293 patients with 303 biopsy-proven BSCs or MBCCs treated with MMS between 1996 and 2004. In total, 32 BSCs and 128 MBCCs were identified. Surgical and follow-up data were analyzed. Kaplan-Meier estimates of recurrence-free survival after MMS were 100% at one year for both tumor subtypes and were 100% for BSC and 93.8% for MBCC at 5 years. Initial mean sizes were 1.5 cm for BSC and 1.3 cm for MBCC. Approximately 7% represented recurrent tumors at surgery. Of six patients with recurrences, none had known metastatic disease. Limitations include retrospective design, analysis of only head and neck sites, and small sample sizes. BSC and MBCC showed no significant distinguishing characteristics to separate them into two BCC subtypes. Reported recurrence rates for BSC and MBCC are 12-45% with wide local excision; estimated recurrence rates are 4.1% with MMS. Our study showed recurrence-free survival of 95.1% at five years. Hence, MMS is effective in treating these BCC subtypes.