Mohs micrographic surgery is a highly effective technique for the removal of some skin cancers. The technique is founded on the idea of excision with minimal margins (sparing normal tissue) and immediate histologic examination of horizontal frozen sections of the specimen while the patient waits. By doing this, a Mohs surgeon is able to examine the margins. If residual tumor is present, subsequent excisions are performed until it is completely removed. In cases of aggressive tumors, recurrent tumors, or in which the lesions are present in high-risk anatomic locations (H-zone of the face) or functionally important areas (e.g., digits, genitals), the preferred treatment is Mohs micrographic surgery.