A melanocytic cuckoo

A 32-year-old man presented with a pigmented lesion on the left dorsal foot for as long as he could remember. Having observed a gradual change in peripheral color over many years, it had become more raised and occasionally itchy in the preceding year. There was no personal or family history of cutaneous malignancy. Clinical examination found a 10-mm × 10-mm symmetrical square plaque with a peripheral tan-colored area surrounding central blue-black pigmentation (Fig 1).