A tender violaceous nodule on the shoulder

A 65-year-old man presented with a 5-year history of a small painful lesion on the left shoulder, with worsening pain during the preceding month prompting medical review. On examination, there was a well-circumscribed reddish–violaceous dome-shaped nodule on the left shoulder, measuring approximately 0.5 × 0.4 cm. The lesion was focally tender on palpation, with no scale, ulceration or bleeding. Polarised dermoscopy demonstrated purplish-red, structureless lacuna-like areas with adjacent pale whitish structureless zones.