Advances in Imaging: In Utero Neck Masses

Congenital neck masses are now more often detected in utero due to high-resolution imaging available with ultrasound and fetal MRI. At our institution, all neck masses are measured to estimate overall volume using the formula for a prolate ellipse, which is the anterior-posterior diameter x width x length x 0.523. Color Doppler is performed in all cases to assess for the presence or absence of internal flow. When echogenic foci are detected, one should evaluate for acoustic shadowing with a narrow sector width. Color Doppler can also be done to assess for twinkle artifacts, which are typical of calcifications. Specific views are taken in both the transverse and longitudinal planes to evaluate the trachea and esophagus. Cine clips are performed to document active swallowing and other motions when present.

Sagittal image of a large cervical teratoma arising from the anterior compartment with mixed cystic and solid components as well as calcifications (arrows). Neck masses — which exclude masses arising from the scalp, mouth and nasal cavity — tend to arise from the anterior, posterior or lateral compartments of the neck. These masses histologically may represent teratomas, lymphatic malformations, hemangiomas, thymic cysts, branchial cleft cysts, cervical myelomeningocele, goiter, etc. Cervical teratomas arise in the anterior compartment and are most commonly mixed cystic and solid masses that can extend to involve surrounding structures. They are often large and can cause neck hyperextension with compression of the trachea and esophagus leading to complications such as polyhydramnios and nonimmune hydrops. Calcifications are common but not absolutely pathognomonic of teratomas.

High-resolution ultrasound and fetal MRI are both capable of characterizing these masses as well as defining their extent. Color Doppler is valuable for the detection of hyper-vascularity within the solid components of these masses. The cervical region is the most common site for teratomas after sacrococcygeal teratomas. Similarly, cervical teratoma should be readily differentiated from epignathus, which is a teratoma that arises from the nasopharyngeal region in which the mouth is virtually always open due to the mass effects of this teratoma.

Lymphatic malformations

3-D image of a cervical lymphangioma extending laterally onto the fetal face. Lymphatic malformations can occur anywhere in the body, but commonly occur in the anterior or posterior neck compartments. These masses are predominantly fluid filled and variable in size. They also often increase during the prenatal period. They tend to be large, infiltrative masses that can extend deep into the mediastinum, superficially onto the face and involve the posterior and lateral neck with displacement or compression of the ears.

The more complex anterior compartment lymphatic malformations can have a mixed appearance with solid and cystic elements as well as calcifications presumably from tissue necrosis. Alternatively, some lymphangiomas can appear almost purely cystic and unilocular. Typically, lymphatic malformations that occur in the posterior compartment have traditionally been referred to as cystic hygromas. They tend to be characteristically multilocular with innumerable thin septate and are relatively avascular on color Doppler. Various syndromes such as Turner syndrome or Noonan syndrome and aneuploidy, specifically trisomy 21, are associated with cystic hygroma.

Congenital hemangiomas

Congenital hemangiomas can occur in the cervical region, most often in the posterior compartment. Since these masses result from abnormal proliferation of vascular endothelial cells, they are generally solid in echotexture, sharply marginated and highly vascular on color Doppler imaging. Tiny echogenic foci can result from intravascular thrombi and arteriovenous shunting can cause non-immune hydrops. On fetal MRI, these masses exhibit intermediate signal on T1 and high signal on T2 sequences.

Image: Transverse image of a hypervascular congenital hemangioma arising from the posterior compartment of the neck, slightly deforming the calvarium (long arrow) and demonstrating the sharply marginated borders, solid echotexture and punctate echogenic foci (short arrow) likely representing intravascular thrombi.

Fetal goiter

Coronal image of a fetal thymic cyst (arrows) extending from the anterior mediastinum into the neck region. The cyst recurred twice following sclerotherapy and was then surgically resected. Fetal goiter is very rare and can be associated with hypothyroidism due to transplacental passage of maternal antithyroid medications. In maternal Graves’ disease, fetal goiter is secondary to transplacental passage of maternal thyroid stimulating IgG antibodies. On ultrasound and MRI, the thyroid appears diffusely enlarged and hypervascular on color Doppler. Rare, predominantly unilocular, purely cystic masses can occur in the neck region and these include thyroglossal duct cysts, branchial cleft cysts and thymic cysts that have extended from the anterior mediastinum into the neck region.

Differentiation of these various types of neck masses should be done as definitively as possible on prenatal scans so that the appropriate parental counseling is provided at the time of the patient’s initial evaluation.