To highlight learning points in management of a lesion initially diagnosed as a keratoacanthoma (KA)

A 42 year-old man was referred from dermatology for a KA in his lateral left brow. The lesion was 22 mm diameter, symmetrical and keratin-plugged. It had appeared 8 weeks ago and the patient reported it was starting to regress. The lesion was excised with 4mm margins, processed conventionally, and reconstructed using a rotational temple flap

Histology showed a squamous cell carcinoma with perineural invasion (PNI) and a very narrow deep margin. Re-excision was deemed necessary and he then required 3 stages of Mohs’ micrographic surgery to achieve clearance. This was largely for lateral rather than deep tumour extension which was completely undetected by the conventional excision margin result. He finally required extensive reconstruction including a bridged segment of a paramedian forehead flap divided after several weeks, and he has since had adjuvant radiotherapy.

Keratoacanthoma is a spontaneously involuting variant of SCC but is typically a lesion of the elderly: be wary of the diagnosis in younger patients and manage accordingly, due to the risk of PNI.
Where skin is short, a bridged segment of a paramedian forehead flap is ideal for lateral brow reconstruction.