Cystic hygroma

Cystic hygroma (CH) refers to a type of congenital lymphangioma 

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%. 

Patients in the infantile or paediatric population can present with pain, dyspnoea, infection, haemorrhage 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 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

Associations

Associated anomalies can be common.

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. 

Antenatal ultrasound

On antenatal 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 poorer fetal outcome 9-10.

CT

Commonly seen as a hypo-attenuating ill defined cystic mass.

MRI

Reported signal characteristics include:

  • T1: predominantly low signal unless there are haemorrhagic components
  • T2: predominantly high signal 
  • T1C+ (Gd): no enhancement on any component except occasional faint enhancement of rim

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 very small 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

Differential considerations on antenatal ultrasound include:

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Article Information

rID: 1190
Section: Pathology
Synonyms or Alternate Spellings:
  • Hygroma colli
  • Cystic hygroma
  • Cystic hygromas
  • Cystic hygromata

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