An irregular dark freckle-like lesion

Case presentation

Over an eight-month period, a 63-year-old man developed an irregular 1 cm diameter freckle-like lesion bounded asymmetrically by a white patch on his upper back (Figure 1). The surrounding skin had extensive freckling and evidence of chronic sun damage. Dermoscopy revealed a pigmented lesion with a markedly irregular pigment network in a coarse and broken pattern. In the centre of the lesion the network was replaced by a pale patch containing blue–black dots and thick blue–black pigment streaks. The network merged with the surrounding mottled sun-damaged skin (Figure 2). Excision biopsy showed an epidermis with confluent proliferation of hyperchromatic small melanocytes, singly and in nests, along the junctional zone (Figure 3). Fibrosis with scattered lymphocytes was evident in the underlying dermis.