An unusual cause of a pigmented lesion

A 65-year-old man presented with a 6-year history of a lesion on his left shin, which had rapidly doubled in size over a period of 6 months. On physical examination, a large, pigmented nodule, 10 · 14 mm in size, was seen on the patient’s shin (Fig. 1a). It was not tender, and was doughy in consistency. Using dermatoscopy, an asymmetrical bluish-grey pigmented area was seen in the centre, while white to whitish-grey pigmented streaks were seen on the periphery of the lesion (Fig 1b). Laterally, there were few faint dotted blood vessels. The lesion was excised under local anaesthesia.