Cystic hygroma

Cystic hygroma, also known as cystic or nuchal lymphangioma, refers to the congenital macrocystic lymphatic malformations that most commonly occur in the cervicofacial regions, particularly at the posterior cervical triangle in infants.

Terminology

While these lesions are commonly known as cystic hygromas or cystic lymphangiomas, the most up-to-date terminology from ISSVA refers to them as macrocystic lymphatic malformations ¹⁴.

Epidemiology 

They usually occur in the fetal/infantile and paediatric populations with most lesions presenting by the age of two. The estimated prevalence in the fetal population is 0.2-3%. 

Associations

Associated anomalies can be common:

• aneuploidic: ~65% (range 50-80%) of cystic hygromas can be associated with an aneuploidic abnormality

  • Turner syndrome: most common aneuploidic association

  • Down syndrome (trisomy 21): second most common aneuploidic association

  • Patau syndrome (trisomy 13)

  • Edwards syndrome (trisomy 18)

  • triploidy ¹¹

• non-aneuploidic

  • congenital cardiac anomalies   

    • aortic coarctation: most common cardiovascular anomaly

    • hypoplastic left heart syndrome

  • pentalogy of Cantrell ⁸

  • Apert syndrome

  • Cornelia de Lange syndrome

  • fetal alcohol syndrome

  • Fryns syndrome ¹¹

  • lethal multiple pterygium syndrome

  • limb hypertrophy

  • Noonan syndrome

  • Pena Shokeir syndrome ¹¹

Clinical presentation

Patients in the infantile or paediatric population can present with pain, dyspnoea, infection, haemorrhage, or respiratory compromise. It is usually found in the posterior triangle of the neck ¹⁵. It can also be found in the axilla. It is compressible and transilluminable.

Pathology

They are thought to arise from delayed development/maldevelopment/failure of the lymphatic system to communicate with the venous system of the neck. Like other lymphangiomas, they are endothelial-lined cavernous lymphatic spaces.

Microscopically, they are comprised of endothelium-lined cystic spaces with scanty stroma. They can vary significantly in size. Lymphatic vascular malformations may be mixed with other forms of vascular malformation, including capillary or venous. 

Location

They occur most commonly in the neck, which is then also termed "nuchal cystic hygroma" (occurs in ~80% of cases) ⁷ and axilla, with only 10% of cases extending to the mediastinum ^2,3 and only 1% confined to the chest ¹. 

Radiographic features

They are usually well-circumscribed and are of fluid density. Cystic hygromas may also have an infiltrative appearance and may be uni or multilocular. The density can also be variable with a combination of fluid, soft-tissue density and fat. 

Ultrasound

On prenatal ultrasound, they may present as a nuchal cyst and may show septations +/- evidence of fetal anasarca/hydrops fetalis. The presence of septations may indicate a poorer outcome. Greater volumes (>75 mm³ according to one study ⁹) are thought to correlate with increased karyotypic abnormality and more unfortunate fetal outcomes ^9,10.

Compared to nuchal translucency, It has a higher risk for aneuploidy (5-fold), cardiac anomalies (12-fold) and fetal demise (6-fold) ¹³.

CT

Commonly seen as a hypoattenuating ill-defined neck cystic mass.

MRI

Reported signal characteristics include:

• T1: predominantly low signal unless there are haemorrhagic components

• T2: predominantly high signal 

• T1 C+ (Gd): no enhancement on any component except occasional faint enhancement of rim

Treatment and prognosis

Management may be by surgical excision and surgical drainage to limit recurrent lymphatic collection.

Injection with OK-432, a preparation containing Streptococcus pyogenes antigens, which induces an inflammatory response and subsequent obliteration of the abnormal cavities.

Most fetuses with cystic hygromas have a poor prognosis although it may improve in utero on its own in a tiny proportion of cases. Spontaneous remission does not necessarily exclude an abnormal karyotype.

Complications

• development of non-immune hydrops fetalis: which often indicates a poorer prognosis

• respiratory obstruction from pharyngeal oedema ¹¹

History and etymology

The first description of cystic hygroma was made by Eugenius Redenbacher, a German physician, in 1828 ¹⁵. The term hygroma, however, was first used by the German surgeon, Adolph Wernher (1809-1883), although he believed the lesion to be neoplastic in nature and unrelated to developmental abnormality ¹⁵. 

The term "hygroma" is derived from the Greek "hygros", meaning moist, as well as "oma", meaning tumour ¹⁶. 

Differential diagnosis

Differential considerations on antenatal ultrasound include:

• cervical teratoma

• occipital encephalocele

• cervical meningocele

See also

• paediatric mediastinal masses

• cystic hygroma vs occipital meningocele