A fast-growing skin lesion in a dialysis patient

One year after kidney transplantation, a 70-year-old man returned to haemodialysis. Induction had consisted in basiliximab, mycophenolate, prednisone and cyclosporine, the latter was switched to tacrolimus after 9 months. Because of rejection under reduced immunosuppression, the graft was removed 6 months after returning to haemodialysis and immunosuppression was completely stopped. Twelve months later, a large skin tumour grew close to the arteriovenous fistula within 4 weeks (Figure 1). A surgical excision was undertaken. Macroscopy showed a spindled skin specimen with a centrally located domeshaped nodule. On histological examination, the tumour presented with crateriform architecture and centrally located papillary proliferation within a keratin plug consistent with the diagnosis of a keratoacanthoma (Figures 2 and 3). Keratoacanthomas are benign skin tumors developing from epidermal and hair follicle keratinocytes. Even after histological examination, keratoacanthomas are hard to