A cystic hygroma is an abnormal growth that usually appears on a babys neck or head. It consists of one or more cysts and tends to grow larger over time. The disorder usually develops while the fetus is still in the uterus, but can also appear after birth.Also known as cystic lymphangioma and macrocystic lymphatic malformation, the growth is often a congenital lymphatic lesion of many small cavities (multiloculated) that can arise anywhere, but is classically found in the left posterior triangle of the neck and armpits. The malformation contains large cyst-like cavities containing lymph, a watery fluid that circulates throughout the lymphatic system. Microscopically, cystic hygroma consists of multiple locules filled with lymph. Deep locules are quite big, but they decrease in size towards the surface. Cystic hygromas are benign, but can be disfiguring. It is a condition which usually affects children; very rarely it can be present in adulthood.Currently, the medical field prefers to use the term lymphatic malformation, because the term cystic hygroma means water tumor. Lymphatic malformation is more commonly used now because it is a sponge-like collection of abnormal growth that contains clear lymphatic fluid. The fluid collects within the cysts or channels, usually in the soft tissue. Cystic hygromas occur when the lymphatic vessels that make up the lymphatic system are not formed properly. The two types of lymphatic malformations are macrocystic  (large cysts) and microcystic (small cysts) lymphatic malformations.
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. Imaging, such as ultrasound or MRI, may provide more information as to the size and extent of the lesion. Treatment
A baby with a prenatally diagnosed cystic hygroma should be delivered in a major medical center equipped to deal with neonatal complications, such as a neonatal intensive care unit. An obstetrician usually decides the method of delivery. If the cystic hygroma is large, a cesarean section may be performed. After birth, infants with a persistent cystic hygroma must be monitored for airway obstruction. A thin needle may be used to reduce the volume of the cystic hygroma to prevent facial deformities and airway obstruction. Close observation of the baby by a neonatologist after birth is recommended. If resolution of the cystic hygroma does not occur before birth, a pediatric surgeon should be consulted.Cystic hygromas that develop in the third trimester, after 30 weeks gestation, or in the postnatal period are usually not associated with chromosome abnormalities. A chance exists of recurrence after surgical removal of the cystic hygroma.