A 50-year-old healthy, asymptomatic white man developed an erythematous papule on the proximal aspect of his left forearm. The lesion grew progressively, and 1 year later, the patient underwent surgical excision. The following month, multiple satellite lesions appeared at the site of the previous excision, as well as on the patient's left hand and the distal aspect of the upper part of his left arm.
On physical examination, the patient was afebrile and had no adenopathy or hepatosplenomegaly. There were multiple erythematous, indurated papules surrounding the previous excision site on the left forearm. A few similar papules were also seen on the distal aspect of the left upper arm area (Figure 1) and on the dorsum of the left hand. A radiograph of the left forearm revealed an ill-defined, expansile lesion on the posterior cortex of the middle of the ulna, and a bone scan showed increased focal uptake within the left ulna. Magnetic resonance imaging demonstrated a 2 × 1-cm soft tissue mass (Figure 2, arrow) in the left antecubital fossa, interpreted as a possible aneurysm of the brachial artery. The mass was resected (Figure 3 and