A mass on the shin

A 55 year old white woman presented with a mass on her shin. It had been present for six months and had an exophytic growth pattern. She reported a history of psoriasis for the past 13 years, for which she had received ciclosporin, a T-lymphocyte immunosuppressant, intermittently for the first 12 years (3 mg/kg for six months each year), and secukinumab, a human monoclonal antibody against interleukin 17A (IL-17A) (300 mg every four weeks), for the past 12 months. She did not report increased sun exposure or use of a tanning bed.

Physical examination revealed a 5×4 cm growth, sparsely scattered with micro-haemorrhages and crusts (fig 1). Popliteal and …