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.
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.
They usually occur in the fetal/infantile and pediatric populations with most lesions presenting by the age of two. The estimated prevalence in the fetal population is 0.2-3%.
Patients in the infantile or pediatric population can present with pain, dyspnea, infection, hemorrhage, or respiratory compromise.
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.
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.
Associated anomalies can be common:
- aneuploidic anomalies: ~65% (range 50-80%) of cystic hygromas can be associated with an aneuploidic abnormality
- congenital cardiac anomalies
- 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
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.
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 outcome 9,10.
Commonly seen as a hypoattenuating ill-defined neck cystic mass.
Reported signal characteristics include:
- T1: predominantly low signal unless there are hemorrhagic components
- T2: predominantly high signal
- T1C+ (Gd): no enhancement on any component except occasional faint enhancement of rim
Treatment and prognosis
Management may be by surgical excision or by 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.
- development of non-immune hydrops fetalis: which often indicates a poorer prognosis
- respiratory obstruction from pharyngeal edema 11
Differential considerations on antenatal ultrasound include:
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- 14. Paul D. Losty, Alan W. Flake, Risto J. Rintala, John M. Hutson, Naomi lwai. Rickham's Neonatal Surgery. (2018) ISBN: 9781447147213