FETAL NECK MASSES

Fetal Neck Masses

Introduction
Cystic Teratoma
Lymphatic Malformation
EXIT procedure
ٗPrognosis

Introduction

The differential diagnoses of fetal neck masses include tumors, vascular malformations, and congenital cysts. Tumors include teratoma, hemangioma, Kaposiform hemangioendothelioma, and neuroblastoma. Vascular malformations include lymphatic and lymphaticovenous malformations. Congenital cysts include thymic, branchial, and duplication cysts. Teratomas and lymphatic malformations comprise more than 90% of all fetal neck masses.

Cystic Teratoma

Prenatal management

Ultrasound performed prenatally can shows a significant solid portion within the mass with possible calcifications, suggesting the diagnosis of a teratoma. The mass is also significantly larger, and polyhydramnios is seen.

A fetal magnetic resonance imaging (MRI) is indicated and will likely provide very useful information that may directly influence prenatal and postnatal management. In addition to assessing the contents of the mass (cystic versus solid versus mixed), the MRI may demonstrate the extent of vascularity, presence of tracheal compression, and presence of any other craniofacial anomalies mass. In addition, the MRI allows for calculation of lung volumes (Observed to expected Lung Volumes), which may predict the possibility of pulmonary hypoplasia

Prenatal complications include polyhydramnios due to esophageal compression and hydrops fetalis due to high output heart failure arising from vascular shunting within the tumor. Polyhydramnios is of special concern in this case since, in combination with the large volume of the mass, it may precipitate sudden early labor. This can be catastrophic since it may not allow for adequate control of the baby ’ s airway, leading to her demise. Frequent ultrasounds, twice weekly or even more frequently, will be required to adequately monitor the fetus and the mother.

Given the size of the mass and evidence of tracheal compression, the fetus is clearly at high risk of airway compromise after delivery. Therefore, an ex- utero intrapartum treatment (EXIT) procedure should be planned. The purpose of the EXIT procedure is to maintain the baby on placental circulation until the airway is secured. Otherwise, immediate asphyxia and death are likely to occur. The EXIT procedure involves the collaboration of an entire team that includes anesthesiologists, obstetricians, pediatric surgeons, neonatologists, and cardiologists. The procedure should therefore be planned and rehearsed well in advance so that all those participating are aware of the condition and progress of the mother and fetus and have clearly assigned roles.

Weekly amnioreductions and aspirations of the dominant cyst are carried out from 27 weeks of gestation onward, with the goal of minimizing esophageal compression and improving fetal swallowing. However, the procedure also carries a risk of inducing premature labor. Therefore, early delivery is indicated to avoid premature rupture of membranes and precipitous labor in this multiparous woman. Antenatal steroids should therefore be given to the mother in anticipation of premature delivery.

How is EXIT procedure performed?

Premature labor requires admission to the hospital for tocolysis at 32 weeks ofgestation, a few days before the planned EXIT procedure. A course of antenatalsteroids is administered. The EXIT procedure is carried out as planned. Afterdeep maternal anesthesia, the placenta is mapped and the uterus is opened with aspecially designed stapler. The fetal head and upper limbs are exposed while therest of the body and the cord remain in utero. A peripheral intravenous line isstarted, and supplemental anesthesia is given to the fetus. Fetal fiberoptictracheoscopy reveals complete tracheal collapse. An endotracheal tube isadvanced under direct vision to just above the carina, where a normal tracheallumen is seen. After successful intubation, the tube is secured with sutures andtape around the neck. The cord is clamped and the baby is“officially” born 40minutes after the head was first exposed. The very large teratoma has to be liftedoff the chest wall to facilitate mechanical ventilation. Resection should be immediately performed. There are no advantages to delayed resection in this case.

The baby is brought into an adjacent operating room and is stabilized by the neonatologists. Laboratory tests, including serum alpha fetoprotein (AFP), are sent. Tumor resection is started 3 hours after birth and proceeds cautiously. Take care of the larynx, pharynx and the carotid artery, internal jugular vein and the vagus nerve.

What histopathology is expected?

Histologic examination of the specimen demonstrates mature tissues derived from all three embryonic germ layers (endoderm, ectoderm, and mesoderm), including respiratory and gastrointestinal epithelium, pancreas, renal glomeruli, bone, cartilage, retina, choroid plexus, and mature glial tissue.

The histologic assessment of pediatric teratoma requires extensive sampling to detect possible malignancy and to ensure that the resection is complete, as these are the most important elements affecting outcome.

This case represents a cervical congenital teratoma. Although yolk sac tumor is the most frequently identified malignant component in congenital teratoma, it is still relatively rare in most sites. It is most frequently identified in congenital sacrococcygeal teratoma, occurring in 10% of cases. Immature neuroepithelial elements are commonly observed. Unlike adult ovarian teratomas, the presence or grade of immature tissue does not predict malignant behavior.

What complications can arise

Significant gastroesophageal reflux (which may require fundoplication before discharge)
vocal cord paralysis on the side of the lesion due to injury of vagus
Paresis of the left marginal mandibular branch of the facial nerve

Malignancy is rarely identified in fetal cervical masses and is not a source of mortality in these patients. Most giant cervical teratomas are benign. In addition to yolk sac tumor, which is the most common malignant element in fetal teratomas, neuroblastoma has also been identified in some neonatal cervical teratomas.

Lymphatic Malformation

The differentiation between increased nuchal translucency and large cystic masses of the neck is again important to emphasize. Nuchal translucency is defined as the presence of a unilocular collection of nuchal fluid in the occipital region, measuring 3 mm or more. It is typically seen in the late first or early second trimester. Sonolucency in the occipital soft tissues, consisting of two symmetrical cavities separated by a midline septum, has been referred to as cystic hygroma, a term which has been erroneously used for all lymphatic malformations of the neck.

Lymphatic malformations can rarely be completely excised. Recurrence rates and resulting deformities after excision are significant. Sclerosis should probably be considered first-line treatment. In patients without airway compromise, a period of observation is warranted as several reports of spontaneous regression have surfaced.

EXIT procedure

EXIT procedures require advanced multidisciplinary planning. Members of an EXIT team include maternal fetal medicine specialists, both pediatric and obstetrical anesthesiologists, pediatric surgeons and/or pediatric head and neck surgeons, and a pediatric cardiologist to continuously monitor cardiac output through a fetal echocardiogram. EXIT procedures should be carried out in centers with significant fetal and neonatal expertise.

Components include:

Its major components include pharmacologic uterine relaxation, accurate placental mapping by ultrasound, an efficient hysterotomy at least 5 cm away from the placental border performed using a special uterine stapler that decreases blood loss
maintaining the fetus partially within the uterine cavity, exposing only the relevant organs, fetal intravenous access in order to directly administer anesthetic agents, and direct monitoring of fetal cardiac function by echocardiography.
Uterine relaxation is induced using inhaled anesthetics, in addition to beta-adrenergic agonists if necessary.
A rapid flow fluid warmer helps maintain the uterine fluid volume and temperature.
If antegrade intubation of the trachea is not possible during an EXIT procedure, the trachea should be identified by dissection through the tumor and intubated retrograde.
A tracheostomy is not recommended, as it does not constitute a stable airway in these patients with massive cervical lesions, and it will also be within the field of dissection during tumor excision

Mortality after an EXIT procedure is frequently due to pulmonary hypoplasia, which may affect up to 30% of these fetuses.

From the maternal perspective, the EXIT procedure requires a general anesthetic during delivery, a longer delivery, and a potential for higher blood loss related to uterine relaxation.

The choice of an EXIT procedure for the treatment of a giant cervical mass has also been analyzed in several studies. Lymphatic malformations are less likely to result in esophageal and airway obstruction as they usually displace the upper aerodigestive tract, rather than compress it. The prenatal diagnosis of teratoma and the presence of polyhydramnios have therefore been found to predict the need for an EXIT procedure.

More recently, a tracheo-esophageal complex displacement index (TEDI) has been described. This index is calculated using MRI by adding the vertical and lateral distances between the tracheo-esophageal complex and the ventral border of the cervical spine. A TEDI greater than 12 mm was found to be predictive of significant airway compromise requiring an EXIT procedure.

Prognosis

The prognosis of lymphatic malformations identified during the second trimester is often confused with that of posterior nuchal translucency, also termed cystic hygroma, identified during the first trimester. Such occipital nuchal translucency/hygroma is known to be associated with chromosomal syndromes, including trisomy 21 and Turner ’ s syndrome, as well as genetic syndromes such as Noonan and Fryns. However, lymphatic malformations identified later in gestation are much less likely to have such associations. Nevertheless, an amniocentesis for karyotyping would be appropriate.

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