Cystic hygroma is a lymph angioma composed of multiloculated, thin-walled cysts. It is typically benign.

A rare congenital malformation, cystic hygroma occurs in approximately 1:12,000 births. Because the malformation is congenital, about 65% of the cases are obvious at birth, whereas the remainder manifest themselves within the first 2 years of life.

Cystic hygroma occurs as the result of a fetus’s failure during gestation to form venous drainage channels. The result is dilated and disorganized lymph channels. The largest of these lymph channels manifest as cystic hygromas. These cysts are most often found in the neck (approximately 75%) with about 20% being found in the axilla. The remaining 5% may be found virtually any place within the lymphatic system. Because of the proximity of the lymphatic system to the neurovascular bundles, these structures are often encompassed by the cystic hygroma.

The signs and symptoms vary, depending on the location of the lesion.