An irregular pigmented lesion on the back

Case presentation

A 52-year-old man had an irregular, 7 mm diameter, pigmented lesion of unknown duration on his mid back. Dermoscopy revealed an asymmetrical, irregularly pigmented lesion that had an accentuated peripheral pigment network with a broken pattern. Irregular pale pigment dots were present within the lesion. The dark pigmented network merged with irregular, light tan, reticulated patches in the surrounding skin. Skin biopsy demonstrated confluent proliferation of atypical melanocytes along the junctional zone and single melanocytes within the epidermis. The upper dermis showed lymphocytic inflammation and melanin pigment.