A cystic hygroma occurs as the baby grows in the womb. It forms from pieces of material that carry fluid and white blood cells. This material is called embryonic lymphatic tissue.

After birth, a cystic hygroma most often looks like a soft bulge under the skin. The cyst may not be found at birth. It typically grows as the child grows. Sometimes it is not noticed until the child is older.

A common symptom is a neck growth. It may be found at birth, or discovered later in an infant after an upper respiratory tract infection (such as a cold).

Sometimes, a cystic hygroma is seen using a pregnancy ultrasound when the baby is still in the womb. This can mean that the baby has a chromosomal problem or other birth defects.

The following tests may be done:

• Chest x-ray
• Ultrasound
• CT scan
• MRI scan

If the condition is detected during a pregnancy ultrasound, other ultrasound tests or amniocentesis may be recommended.

Treatment involves removing all of the abnormal tissue. However, cystic hygromas can often grow, making it impossible to remove all of the tissue.

Other treatments have been tried with only limited success. These include:

• Chemotherapy medicines
• Injection of sclerosing medicines into the cystic hygroma
• Radiation therapy
• Steroids

The outlook is good if surgery can totally remove the abnormal tissue. In cases where complete removal is not possible, the cystic hygroma commonly returns.

The long-term outcome may also depend on what other chromosomal abnormalities or birth defects, if any, are present.

Complications may include:

• Bleeding
• Damage to structures in the neck caused by surgery
• Infection
• Return of the cystic hygroma

If you notice a lump in your neck or your child's neck, contact your health care provider.

Lymphangioma; Lymphatic malformation

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Kelly M, Tower RL, Camitta BM. Abnormalities of lymphatic vessels. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 516.

Marcdante KJ, Kliegman RM, Schuh AM. Lower airway, parenchymal, and pulmonary vascular diseases. In: Marcdante KJ, Kliegman RM, Schuh AM, eds. Nelson Essentials of Pediatrics. 9th ed. Philadelphia, PA: Elsevier; 2023:chap 136.

Richards DS. Obstetric ultrasound: imaging, dating, growth, and anomaly. In: Landon MB, Galan HL, Jauniaux ERM, et al, eds. Gabbe's Obstetrics: Normal and Problem Pregnancies. 8th ed. Philadelphia, PA: Elsevier; 2021:chap 9.

Updated by: Josef Shargorodsky, MD, MPH, Johns Hopkins University School of Medicine, Baltimore, MD. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.