Cystic Hygroma

Cystic hygromas are varying sized cystic abnormalities of the lymphatic system occurring in perhaps 1 in 10,000 births. The word is derived from the Greek meaning moist or watery tumor and can occur equally in boys and girls. Approximately 50 or 60 percent are present at birth and about 80-90 percent appear or are detected before the end of the second year of life.

Embryology: Their cause is related to lymph channel development of the lymphatic system and may be due to poor communication with developing veins, which result in isolated sacs or little blind ends. These sacs slowly enlarge (filled with fluid) and may seem to infiltrate into surrounding tissues or push other tissues aside.

Figure 1. Characteristic large neck cystic hygroma present since birth in 3-month-old boy

Cystic hygromas present generally as a multicystic mass with thin walls, and being fragile they may have areas of bleeding or accumulation of blood within them. They usually reside in close association with large veins and known lymphatic ducts in the neck, axillary area, groin area, or may infiltrate any areas of the skin along the trunk, extremities, or inside the chest or abdomen (Figure 1).

They present as soft, discrete, and nontender swellings that are often compressible. Cysts within the mass vary from a very small size of a few millimeters to one of several centimeters. In some cases the hygroma may involve two or more areas by direct extension and seem to occur on the left side of the neck twice as often as the right, possibly related to the development of a large lymphatic structure in the chest which empties into the left internal jugular vein (Figure 2).

Figure 2. Axillary cystic hygroma extending beneath the collar bone from a smaller cystic lesion in the neck.

Most are noted shortly after birth and seem to gradually enlarge as they fill. They may expand as a result of bleeding into them or infection, in which case they may become tender or hurt and the overlying skin will have an inflamed or red appearance. It is common for a bluish color to appear under the skin, even though the liquid is clear, and the color of ginger-ale. In the neck the cysts can extend downward into the chest and on rare occasion may produce breathing difficulty because of pressure on the airway or difficulty with swallowing with resultant failure of the child to grow because of his or her inability to eat without discomfort.

Infection in a cystic hygroma may cause rapid enlargement and pain and respond slowly to antibiotic therapy. When this occurs, there is some scarring in the cystic hygroma, as well as the tissue adjacent to it, which may complicate surgical therapy. Although usually recognizable by physical examination alone, sometimes the use of imaging studies, such as ultrasonography and computed tomography (CAT scan), are helpful in distinguishing cystic hygromas from solid masses.

TREATMENT
Cystic hygromas rarely go away on their own. Aspiration by puncturing with a needle is usually followed by prompt reaccumulation of fluid or development of infection. Injection of chemical agents to cause shrinkage is effective in certain hygromas where there are large cysts, but is not as effective when there are very small cysts. This is not without potential complications, and as yet there is no universal agent available that is totally safe.

When infection occurs, it is necessary for the child to be treated with antibiotics, yet definitive treatment may rest in surgical removal once the infection is controlled. Most pediatric surgeons defer surgery until approximately six months of age if the rate of enlargement does not exceed general body growth. Complete removal is challenging and reoccurrence may be 5 or 10 percent, even in favorable cases. Although all efforts are made to remove remnants of the cyst, because it is non-cancerous no major nerves or other important structures should be removed when removing the cysts.