Will MAC be back?

Background: Microcystic adnexal carcinoma (MAC) was first described as a specific entity in 1982 by Goldstein et al. MAC is a very aggressive tumour, displaying locally invasive tendencies with perineural invasion. For this reason previous studies have suggested that Mohs micrographic surgery is a superior technique in establishing clear margins of excision. However, there is no evidence to suggest that standard local excision is less effective in achieving tumour clearance or a more favourable outcome. Methods: All patients with MAC were identified from the pathology database. All patients who had undergone local excision were reviewed and included in the study. Histopathology was reviewed by dermatopathologists. Results: We reviewed the outcome of 17 patients treated with local excision. Eleven were female and six were male with a mean age of 70 years, and a mean follow up of 30 months. Two patients in this series experienced recurrence after standard local excision. The mean lateral and depth margins were 7.69 mm (range 0.2-21) and 4.66 mm (range 1-14.5), respectively. Recurrence occurred in two out of three patients who had lateral clearance margins of less than 4 mm. These two patients had evidence of perineural invasion on histopathology. Conclusion: In the present study, standard local excision is shown to be effective in tumour clearance for MAC with no recurrences provided there are lateral margins of at least 4 mm. However, a longer period of follow up is required because of the very aggressive locally invasive nature of the tumour.