A cystic hygroma is a rare, fluid-filled sac resulting from a developmental issue during the formation of the lymphatic system. These growths are congenital, meaning they are present at birth, and they often appear as a soft bulge. The condition is essentially a collection of fluid caused by a localized problem in the body’s drainage system.
Understanding the Condition
A cystic hygroma is classified as a type of lymphangioma, a malformation of the lymphatic system. The lymphatic system transports lymph fluid throughout the body. A cystic hygroma forms when lymphatic vessels fail to properly connect to the venous system, causing fluid to accumulate in localized sacs.
These sacs are thin-walled and often multiloculated, containing multiple distinct compartments. While they can arise anywhere, approximately 75% of cystic hygromas are found in the head and neck region, with other common sites being the axilla, groin, and chest wall. They are categorized into macrocystic (large cysts) and microcystic (small cysts). Macrocystic lesions tend to respond more favorably to non-surgical treatments.
Underlying Causes
The precise etiology of cystic hygroma is often unknown. The condition is fundamentally a developmental error that occurs early in fetal growth, typically between the ninth and sixteenth week of pregnancy, when the lymph sacs are forming. The malformation arises from the failure of embryonic lymphatic tissue to establish communication with the venous drainage system.
There is a significant association between cystic hygromas and the presence of chromosomal abnormalities, which are found in approximately 35% to 50% of cases detected prenatally. Specific genetic conditions frequently linked to the finding include Turner Syndrome (45,X), Down Syndrome (Trisomy 21), and Trisomies 13 and 18. In cases where the fetus has a normal set of chromosomes, the condition is usually an isolated failure of lymphatic drainage or may be associated with non-chromosomal syndromes like Noonan syndrome.
Detection and Diagnosis
Diagnosis of a cystic hygroma frequently occurs during the prenatal period, often through routine obstetric ultrasounds. The finding is closely related to the nuchal translucency (NT) screening, a first-trimester ultrasound measurement of the fluid-filled space at the back of the fetus’s neck. A cystic hygroma appears as a larger, septated, fluid-filled structure, differentiating it from a simple increase in nuchal edema.
Once a cystic hygroma is identified, advanced imaging, such as detailed anatomy scans, confirms the size, location, and extent of the lesion. This assessment helps determine if the growth is impacting structures like the airway or surrounding blood vessels. Invasive testing, such as chorionic villus sampling (CVS) or amniocentesis, is typically offered to check for associated chromosomal conditions. Postnatal diagnosis is confirmed through physical examination, and imaging studies like MRI or CT scans are used to map the full extent of the malformation before treatment planning.
Medical Management and Treatment
The management plan for a cystic hygroma is highly individualized and is determined by the lesion’s size, location, and the presence of any symptoms, such as difficulty breathing. For very small, non-obstructive lesions, a period of expectant management, or watchful waiting, may be initially recommended. This approach acknowledges that some cystic hygromas can spontaneously shrink or resolve over time.
For lesions that are causing symptoms, growing rapidly, or are cosmetically concerning, intervention is necessary. Surgical excision remains a primary treatment option, particularly for well-defined and easily accessible growths. The goal of surgery is to achieve complete removal of the abnormal tissue to prevent recurrence, but the complexity of the procedure increases significantly if the hygroma is close to nerves or other vital structures.
A non-surgical alternative, sclerotherapy, involves injecting a sclerosing agent directly into the cyst to cause inflammation, leading to scarring and shrinkage. Agents commonly used include bleomycin and OK-432, which are effective in reducing the size of macrocystic lesions. Sclerotherapy is often favored for lesions difficult to access surgically or as a first-line treatment.
Outlook and Follow-Up Care
The long-term outlook for an individual diagnosed with a cystic hygroma varies significantly and depends on two major factors: the presence of associated chromosomal abnormalities and the size and location of the lesion. Fetuses with an abnormal karyotype, such as Turner Syndrome, have a poorer prognosis, often involving a high risk of other structural anomalies like heart defects. However, for those with a normal chromosome makeup and no other structural malformations, the chance of a healthy outcome is much higher.
Even after successful treatment, there is a risk of recurrence, estimated to be around 15% following surgical removal, particularly if residual tissue remains. Long-term monitoring by a multidisciplinary team, including pediatric surgeons and geneticists, is required throughout childhood. This follow-up ensures that recurrence is detected early and that potential long-term issues, such as those affecting the airway or cosmetic appearance, are addressed.