A review of the evidence for Mohs micrographic surgery. Part 2: basal cell carcinoma.

Mohs micrographic surgery (MMS) is considered the gold-standard treatment for basal cell carcinoma (BCC) particularly for sites with a high-risk of incomplete excision such as the central face, for tumours with an aggressive growth pattern and consequent unpredictable subclinical extension and for recurrent tumours. However, the process is more time-consuming than for standard excision (SE), and the magnitude of benefit is uncertain. This article aims to provide a more complete picture of current evidence, including a review of cosmetic outcomes, tissue-sparing ability and cost-effectiveness of MMS. Although robust evidence is lacking, there is a large volume of observational data supporting a low recurrence rate after MMS. The risk of incomplete excision and higher recurrence rate of standard excision favours the use of MMS at high-risk sites. There is some low-certainty evidence that MMS results in a smaller defect size compared with SE, and that incomplete excision with SE results in larger defects. Larger defects may affect cosmetic outcome but there is no direct evidence that MMS improves cosmetic outcome compared with SE. There is conflicting evidence regarding the cost of MMS compared with SE, as some studies consider MMS less expensive than SE and others consider it more expensive, which may reflect the healthcare setting. A multicentre 10-year randomized controlled trial comparing MMS and SE in the treatment of high-risk BCC would be desirable, but is unlikely to be feasible or ethical. Collection of robust registry data capturing both MMS and SE outcomes would provide additional long-term outcomes.