A mottled blue–grey lesion

Case presentation

Over a six-month period, a 73-year-old man noticed that a longstanding tan-coloured lesion on the posterior aspect of his left calf had changed in colour (Figure 1). The lesion measured 1.5 cm in diameter. Under dermoscopy, it had a mottled blue–grey colour, with a patchy pale veil. There were pigmented dots and globules but no well-developed pigment network (Figure 2). Skin biopsy revealed an irregular epidermis with underlying superficial lymphocytic inflammation and melanin pigment. There was no melanocytic proliferation or nests present within the junctional zone (Figure 3).