A 10-week-old boy presented with a nodule on his left knee that had been noted at birth. The nodule, which was initally approximately 1 cm in diameter, had rapidly enlarged, reddened, and developed prominent telangiectasias. There was no history of trauma, and the patient's medical history and family history were unremarkable.
Physical examination revealed a 3-cm indurated nodule with central erythema and telangiectasias on the lateral aspect of the left knee (Figure 1). Joint mobility was normal. An excisional biopsy specimen was obtained (Figure 2 and Figure 3).