A saccular lesion

Case presentation

A 74-year-old woman noted the sudden appearance of a dark papule on her right knee (Figure 1). Dermoscopy revealed a mosaic of closely set, small, dark red saccules surrounded by larger blue–black and red saccules that were obscured by a milky veil. The lesion had smooth, rounded borders and lacked a visible pigment network (Figure 2). Skin biopsy demonstrated a series of vessels with fresh or organised thrombi, along with a smooth lining of endothelial cells (Figure 3).