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Cystic hygroma

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"cystic hygroma" OR "cystic lymphangioma"

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cystic hygroma fetal ultrasound neck

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Cystic Hygroma

Definition

A cystic hygroma is a congenital thin-walled cyst containing lymphatic fluid, arising from failure of the primitive lymphatic tree to connect to the venous system — the blind lymphatic pouch dilates to form a macrocystic lymphatic malformation (also called cystic lymphangioma, lymphatic hamartoma, or hygroma cysticum). It is multiloculated, lined by endothelium, and most commonly involves the posterior neck/jugular lymphatic sacs.

Epidemiology & Pathogenesis

  • Incidence: 1:100 pregnancies in the first trimester; septated subtype in 1:285 pregnancies
  • Arises from failure of the jugular lymphatic sac to drain into the venous system → lymphatic obstruction → cystic dilation
  • Can occur anywhere along the lymphatic system: posterior neck (most common), axilla, mediastinum, groin, retroperitoneum

Clinical Features

Prenatal (most commonly detected):
  • Anechoic, fluid-filled posterior neck mass — septated or simple
  • A thick midline nuchal ligament band is characteristic (separating bilateral jugular sacs)
  • May engulf the fetal head cephalad, or extend caudad over the dorsum
  • Associated with fetal hydrops in severe cases
Postnatal:
  • Soft, translucent, cystic neck mass, often large
  • Can distort the airway — potentially life-threatening
  • Prone to sudden enlargement from intracystic hemorrhage or infection (becomes tender, tense, purple/yellow)

Associated Anomalies (Prenatal)

Structural anomalies in ~34% of first-trimester cases:
CategorySpecifics
Aneuploidy (50%)Turner syndrome (45,X) — 28.3%; Trisomy 18 — 19.4%; Trisomy 13 — 9%; Triploidy — 4.5%
Cardiac anomalies72.7% of structural abnormalities — hypoplastic left/right heart, TOF, VSD, complex defects; 4.3% major CHD in euploid fetuses
SyndromesNoonan syndrome, Roberts syndrome, Cornelia de Lange, others
OtherSkeletal abnormalities, fetal hydrops, IUFD

Imaging

Ultrasound (Key Diagnostic Features)

  • Anechoic, fluid-filled cavities in the posterior neck
  • Thick or thin internal septations
  • Thick midline nuchal ligament (Turner syndrome classic)
  • May be multiloculated
Septated cystic hygroma on transverse fetal ultrasound — anechoic cystic mass in posterior cervical region with internal septation dividing fluid into compartments
Large cystic hygroma with hydrops — septated nuchal cystic structure with diffuse fetal edema
Turner syndrome — bilateral cystic neck mass with thick midline nuchal ligament

MRI

Useful postnatally to define extent of lymphatic channels and airway relationship.

Differential Diagnosis

  • Thickened nuchal translucency (non-septated)
  • Neural tube defects (posterior encephalocele, cervical meningocele)
  • Cystic teratoma
  • Hemangioma
  • Thyroglossal duct cyst / branchial cleft cyst
  • Laryngocele
  • Fetal hydrops

Management

Antenatal

  1. Detailed fetal anatomy survey to identify associated anomalies
  2. Fetal echocardiogram (cardiac anomalies present in majority of structural abnormalities)
  3. Genetic testing — amniocentesis or CVS for karyotype/chromosomal microarray
  4. Serial ultrasounds for growth, hydrops, polyhydramnios from esophageal compression, progression
  5. Assess airway relationship for birth planning

Delivery

  • If large cystic neck mass compromises the airway: EXIT procedure (ex utero intrapartum treatment) — secures airway while uteroplacental circulation is maintained

Postnatal / Pediatric Surgical

  • Complete surgical excision with meticulous isolation and ligation of lymphatic branches; avoid blunt/electrocautery dissection (risk of recurrence/infection)
  • When complete excision is not feasible: sclerotherapy with bleomycin, doxycycline, or OK-432 (Picibanil, derived from Streptococcus pyogenes)
  • Sirolimus (mTOR inhibitor) is emerging as a pharmacologic option, particularly for cervicofacial disease

Prognosis

  • Highly variable — depends on karyotype, associated anomalies, and trimester at detection
  • In the presence of aneuploidy or hydrops: poor prognosis, high rate of IUFD
  • Euploid fetuses with isolated hygroma: better outcome but still significant risk of CHD
  • Spontaneous resolution can occur (particularly with small, non-septated lesions early in pregnancy)
  • A 2025 systematic review (PMID: 40389136) confirmed that perinatal outcomes are strongly stratified by chromosomal status and presence of hydrops
  • A 2025 review (PMID: 40190084) highlighted the genetic link between cystic hygroma, nuchal translucency, and congenital heart disease via cardiac lymphatic abnormalities
Sources: Creasy & Resnik's Maternal-Fetal Medicine (8e); Sabiston Textbook of Surgery; Dermatology 2-Volume Set (5e); Thompson & Thompson Genetics in Medicine (9e)
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