Neck masses

Fetal Neck Masses

Abnormalities of the fetal neck are uncommon and may not be apparent during the 18-20 week fetal anatomy scan. The most important abnormalities are cystic hygroma, neck neural tube defects (occipital encephalocele, cervical meningomyelocele) and neck tumors (teratoma). Rarely a fetal thyroid enlargement (goitre) may be detected. Information from the ultrasound on whether the mass is cystic or solid, its position and extent can help to establish the diagnosis. An accurate diagnosis is important as it influences management. Serial scans are performed to update findings as this may affect the prognosis as well as the mode of delivery.

The outcome, both in the short and long term will depend on the actual diagnosis.

Cystic Hygroma

This is a lymphatic abnormality which forms a cystic mass at the back of the fetal neck. It is often detected at the 11-14 week ultrasound (see section on Nuchal Translucency Ultrasound which usually accompanies the first part of blood prenatal screening). Cystic hygroma has a high incidence of chromosomal disease, heart abnormalities, syndromes such as Noonan syndrome and hydrops (fluid accumulation in the fetus). The most common chromosomal abnormality is Turner syndrome (45XO) which occurs in about 75% but a minority have trisomy 21 (Down syndrome) and trisomy 18 (Edwards syndrome).

Chromosome testing (see sections on Amniocentesis and Chorionic Villus Sampling) and fetal heart ultrasound (echocardiography) are recommended and management depends on the diagnosis. Cystic hygroma with hydrops has a very poor prognosis but without hydrops, they usually regress completely.

Neck Neural Tube Defects

Occipital encephalocele results from a skull defect and herniation of brain tissue through the defect. It occurs in between 1 in 5000-10000 pregnancies. There are associated abnormalities in the head. The outlook is generally poor and the majority of survivors have intellectual disability.

See also section on Myelomeningocele (Spina Bifida)

Neck Teratoma

These are rare tumors. The majority are benign but can be large and are associated with excessive amniotic fluid because of compression of the esophagus. On ultrasound assessment, the tumors are usually solid with cystic components and can produce hyperextension of the fetal neck. Urgent treatment is required at delivery so that an airway can be established to prevent respiratory distress.

Thyroid Enlargement / Goitre

Goitres can be associated with hypothyroidism (most common) or hyperthyroidism. Congenital hypothyroidism occurs in about 1 in 5000 live births and is usually caused by treatment with antithyroid drugs for maternal hyperthyroidism. The fetal thyroid is visibly enlarged on ultrasound. The prognosis depends on the cause and can be associated with excessive amniotic fluid from neck compression.

Special Pregnancy Program

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Fetal Medicine: 416-586-4800 x 7756
Fax: 416-586-3216

Maternal Medicine: 416-586-4800 x 7000
Fax: 416-586-5109

Main clinic hours: Monday to Friday, 8am to 4pm

Prenatal Diagnosis & Medical Genetics

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phone: 416-586-4800 x 4523
fax numbers:
416-586-4723 or 416-586-8384

Perinatal Mental Health

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Phone: 416-586-4800 x 8325
Fax: 416-586-8596