Fetal Neck Masses
· Cystic hygroma- Cystic hygromas are multiseptate cystic masses, often bilateral, located posterolaterally along the neck. The majority (75%) are associated with abnormal karyotypes, therefore a karyotyping procedure is appropriate. CH is associated with trisomies 21, 18 and 13 and several syndromes including Turner’s, Noonan’s, Roberts’, Cumming’s, Lowchock’s and lethal multiple pterygium. It has also been reported with achondrogenesis type II and teratogens such as alcohol, aminopterin and trimethadone. PH and hydrops are frequently associated. They tend to regress as pregnancy advances. In a karyotypically normal fetus with no associated US abnormalities the outcome is usually good.
· Psudomembrane- Described by Hertzberg et al, it is felt to be secondary specular reflection from the developing skin on the back of the neck in early pregnancy. This ‘artifact’ is difficult to differentiate from small CR. However, a pseudomembrane is usually seen in fetuses in a ‘neck up’ position, and is seldom multiseptate. It is thought that at least some of the CR detected at 9—15 weeks and which showed spontaneous resolution may be related to a ‘pseudomembrane’.
· Nuchal thickening- Nuchal skin thickening is measured on an axial plane which includes the cisterna magna and the cavum septum pellucidum. The nuchal skin is regarded as abnormally thick if the distance between the calvarium and the dorsal skin boundary is 6 mm or greater in the second trimester, and indicates the need for karyotyping. The anomaly accompanies various chromosomal aberrations, particularly trisomy 21, Escobar’s and Zellweger’s syndromes and Klippel—Feil sequence.
· Goitre- This may present as a solid bibbed mass with some echolucent areas. Its location will suggest its origin. Typical appearances and location will not cause confusion with teratomas. However, thyroid teratoma diagnosed as goitre has been described. Fetal goitre may decrease in size with maternal treatment. Causes of fetal goitre include maternal ingestion of iodides, maternal ingestion of anti- thyroid drugs, endemic iodine deficiency and autosomal recessive enzyme deficiency.
· Hemangioma- Hemangiomas can occasionally appear in the neck region. They usually have a mixed or solid appearance. Actual pulsations or flow helps to identify their origin. Duplex Doppler is a useful adjunct.
· Branchial cleft cyst- This represents an anterolateral neck mass, usually cystic and unibocular. There are usually no associated anomalies.
· Teratoma- This neck mass may be cystic, mixed or solid and may show continuous growth in utero. The masses are usually benign and present as a lobular complex appearance. Calcification is frequent. Associated anomalies include hemangiomas, branchial cysts and PH.
· Neuroblastoma- Neuroblastoma metastases to the subcutaneous tissues of the neck have been detected antenatally; these matastases should not be confused with a goitre because of the asymmetric placement.
· Encephalocele- This is usually an occipital mass but may be low enough to enter the differential diagnosis of a neck mass. Demonstration of a bony defect is necessary to make a diagnosis. Associated ventricular dilatation may be evident.
· Thyroglossal cyst- Thyrogbossal cyst is usually a unilocular mass which presents in the midline and, unlike a teratoma, has no solid elements.
· Sarcoma- Undifferentiated sarcoma has been detected antenatally. It presents as a solid unilateral neck mass with PH.
· Klipple-Trenaunay-Weber syndrome- A large multiloculated mass in the anterior neck has been reported in utero, associated with subcutaneous cystic lesion in an extremity.
· Cervical meningocele- This is associated with a spinal arch abnormality.
· Nuchal translucency- Measured from the cervical vertebrae to the skin surface, >3 mm at 10—16 weeks has an increased incidence of aneuploidy. Karyotyping should be considered.
