The malformation contains large cyst-like cavities containing lymph, a watery fluid that circulates throughout the lymphatic system.

A lethal version[6] of this condition exists, known as Cowchock–Wapner–Kurtz syndrome, that, in addition to cystic hygroma, includes cleft palate and lymphedema, a condition of localized edema and tissue swelling caused by a compromised lymphatic system.

In addition, cystic hygromas can be found in other body parts, such as the arms, chest, legs, groin, and buttocks.

Detection of a cystic malformation may prompt further investigation, such as amniocentesis, to evaluate for genetic abnormalities in the fetus.

Lymphatic malformations may be discovered postnatally or in older children/adults, and most commonly present as a mass or as an incidental finding during medical imaging.

Verification of the diagnosis may require more testing, as multiple cystic masses can arise in children.

A thin needle may be used to reduce the volume of the cystic hygroma to prevent facial deformities and airway obstruction.

[10] Cystic hygromas that develop in the third trimester, after 30 weeks' gestation, or in the postnatal period are usually not associated with chromosome abnormalities.