Clavicular overgrowth in association with cystic hygroma.

Cystic hygroma is a rare congenital abnormality of the lymphatic system of the neck which is now considered to form part of a spectrum of lymphangiomatous malformations. Lytic bone lesions are described in systemic lymphangiomatosis and bony overgrowth (hemihypertrophy) in association with angiomatous malformations of the limbs. Two infants with ipsilateral clavicular overgrowth adjacent to cystic hygromas are reported. This association has not been recorded previously; the possible etiology is discussed.