Pathology of the Fetal Neck

Fetal neck is the site of important pathological changes, related to genetic, cardiovascular, lymphatic, endocrine systems. Among the main neck pathology are fetal hygroma, goiter, teratoma/sarcoma, hemangioma/lymphangioma. Posterior anomalies of the fetal neural tube, such as occipital myelomeningocele or iniencephaly may also be included in this area. Fetal hygroma is the main pathology, probably related to abnormal development of the lymphatic drainage system. There is a large spectrum of the disease, from enlarged nuchal translucency to generalized edema. Enlarged nuchal translucency is often associated with aneuploidy, particularly trisomy 21 and Turner syndrome (monosomy X). However, the pathophysiology is different for the two aneuploidies. On the diagnostic side, cystic hygromas consist of large single or multilocular fluid-filled cavities, which are usually easily identified during first trimester ultrasound examination. About one-third of euploid fetuses with first trimester septated cystic hygromas have major structural anomalies. In contrast, structural anomalies are detected in only 4 to 10% of euploid fetuses with enlarged nuchal translucency. Enlargement of fetal thyroid gland is accompanied by increased or decreased level of thyroid hormones (hyper or hypothyroidism), but the thyroid function may also be normal. The physiopathology of fetal and neonatal goiter is complex. Causes of fetal goiter include inborn errors of thyroid hormone production, transplacental passage of maternal antibodies, maternal ingestion of antithyroid drugs and other goitrogens, thyroid tumors. Detection of the fetal goiter is facilitated by the associated maternal history, present in most of the cases. By definition, goiter means enlargement of the thyroid gland above the 95th centile of the normal range. Reliable and objective data about fetal thyroid function involves an invasive testing. Teratomas are large mixed tumors arising from the neck region. Teratomas are cystic, semicystic or solid tumors. They develop from all three germ cell layers. Cervical teratomas are detected antenatally in most cases, as they are large size tumors. Hemangiomas and lymphangiomas are tumors derived from the endothelial tissue of blood vessels or lymphatic vessels. They may develop anywhere in the body, but in the antenatal life and the first years they show a predisposition for the head, neck and axillar area. Regarding the occipital encephalocele and iniencephaly, even though they represent major anomalies that affect he cervical and cephalic area, from a developmental point of view they are part of the neural tube defects spectrum and should be considered as such especially from a prognosis point of view.