This lesion on her knee had been present for 5 years, reported a 22- year-old woman. It was not related to any trauma; its size had not changed, but occasionally it became darker or lighter. Excisional biopsy revealed lymphangioma circumscriptum—a benign, hamartomatous malformation of dilated lymph channels that may be filled with clear fluid because of communication with deeper lymphatics or, as in this case, serosanguinous fluid. Treatment (excisional biopsy) is indicated primarily for diagnosis, cosmetic reasons, and relief of patient anxiety, writes Dr Robert P. Blereau of Morgan City, La, but it also prevents leakage of fluid and infection. The deep communicating lymphatic cistern must also be excised, otherwise lesions likely will recur.