Misdiagnosed microcystic adnexal carcinoma on the lateral forehead and challenges in reconstruction of a large and bone-deep defect.

BACKGROUND

Microcystic adnexal carcinoma (MAC) is a rare cutaneous malignancy characterized by aggressive local infiltration, including a high propensity for perineural invasion. Histologically it can be easily confused with benign adnexal tumors, which often leads to inappropriate initial treatment. As a consequence delayed surgical excision often requires removal of large cutaneous masses which can be followed by challenges in reconstruction.

METHODS

We report the case of a challenging reconstruction of a large forehead defect by a modified AT flap with central Burow's triangle grafting and previous wound conditioning using hyaluronic acid after complete micrographic removal of MAC.

RESULTS

A 80-year-old healthy female presented with an almost six year history of an asymptomatic slowly progressing skin mass previously biopsied and diagnosed as benign syringoma five years in advance. Deep biopsies confirmed MAC. She underwent staged surgical excision with Tübingen torte technique with removal of the frontal periostium. A skin substitute of esterified hyaluronic acid was applied for three weeks to the bone-deep 6 × 7 cm defect leading to good granulation tissue above the bone. Final reconstruction was achieved by an AT flap combined with full thickness skin transplantation of the central dog ear. The cosmetic outcome was satisfactory, no recurrence was observed within 18 months follow-up.

CONCLUSIONS

We confirm the histological difficulties in the diagnosis of this tumor entity and the large extension of MAC due to delay in diagnosis and treatment. Deep tumor removal including the periostium might be necessary to achieve tumor free margins. Fast granulation tissue above the frontal bone might be achieved by applying hyaluronic acid products. The combination an AT flap with transplantation of the adjacent Burow's triangles gives optimal skin texture and color matching and seems to be a good option to close even large defects of the front especially for supra brow defects.