Microcystic adnexal carcinoma: a report of three cases.

Microcystic adnexal carcinoma is an uncommon adnexal neoplasm. It is highly aggressive locally and its importance lies in the fact that it can be easily confused with benign adnexal tumours, particularly desmoplastic trichoepithelioma, trichoadenoma and syringoma. We report three cases of microcystic adnexal carcinoma of the skin, all three being on the face: two on the lips and one on the left eyebrow. Clinically, the neoplasms were slow growing indurated nodules or plaques. Two of the cases displayed benign features on initial biopsy and their malignant potential could not be established at that stage. On subsequent review, the three neoplasms showed all the characteristic features of microcystic adnexal carcinoma as described by Goldstein et al. and the University of Virginia study. All three patients were treated by surgery in the form of wide excision. They behaved in a highly locally malignant manner with excisions being incomplete in two of the lesions, in spite of taking an adequate margin around the clinically assessable margins. The other recurred after three years in spite of a histologically proven complete excision. Two of the tumours showed infiltration into the underlying muscle with perineural spread. Wider excision in the next stage with frozen section control achieved good clearance and after a five year follow-up period all are symptom free. None of these tumours showed any evidence of distant spread.