Microcystic adnexal carcinoma: a case series treated with mohs micrographic surgery and identification of patients in whom paraffin sections may be preferable.

BACKGROUND: Microcystic adnexal carcinoma (MAC) is a rare cutaneous tumor characterized by aggressive local infiltration, including a high propensity for perineural invasion (PNI). OBJECTIVES: To report our experience in treating MAC using Mohs micrographic surgery (MMS) with frozen sections and to identify patients in whom that technique may have limitations. MATERIALS & METHODS: A review of records between 1992 and 2008. RESULTS: Nine patients with MAC were identified. All tumors were located on the face. PNI was noted in the diagnostic biopsies of two patients with periocular MAC, in both of whom tumor persisted after MMS. The mean duration of follow-up was 5.4 years. CONCLUSIONS: MMS with frozen sections is reliable for treating primary MAC in which PNI is not present on a diagnostic biopsy. Previous surgery and PNI were associated with greater risk of persistence in periocular MAC. In these patients, it may be appropriate to consider MMS with paraffin-embedded sections, possibly as a layer after apparent clearance on frozen sections. Further excision of orbital contents should be considered in periocular MAC that infiltrate the deep orbital fat or are noted to have PNI.