Retrotracheal Secondary Intrathoracic Goiter Presenting as Cervical Thyroid Nodules on Ultrasonography

Dear Editor:

Retrotracheal goiters are rarely diagnosed at the cervical level (i.e., above the plane of the thoracic inlet). Here we describe a patient with a cervical retrotracheal thyroid goiter with extension into the intrathoracic retrotracheal region whose initial ultrasonography (US) examination suggested a thyroid nodule on both the right and left side, each with retrotracheal extension. Computed tomography (CT) was required to define the true anatomical nature of what turned out to be one lesion.

An asymptomatic 35-year-old woman was referred to our department for thyroid US examination because her brother had been operated from papillary thyroid carcinoma 3 months earlier. On clinical examination the thyroid was palpable and without nodularity. The serum thyrotropin was normal. US showed normally structured thyroid lobes, but closer examination revealed that behind the lower halves of both lobes there were slightly hypoechogenic thyroid nodules, one on each side, that extended caudally for about 4 cm and also medially. The medial extension was interrupted by the tracheal shadow, so that the medial borders could not be identified. It seemed that the patient had two thyroid nodules with retrotracheal extension. US-guided fine-needle aspiration cytology of these nodules showed follicular thyroid structure with atypical thyrocytes in the left nodule. Tc-99m-pertechnetate scintigraphy displayed only the normal thyroid lobes. CT of the neck (see Supplementary Data, available online at www.liebertonline.com/thy) disclosed a single nodule originating from the thyroid, measuring 4.7 × 4.4 cm. It extended to behind the lower halves of both thyroid lobes as well as downward into the intrathoracic retrotracheal region, encircling, but not compressing, the trachea. To establish the diagnosis, and minimize the possibility of compression of the trachea in the future, surgery was performed through a left cervical incision. Intraoperative examination confirmed that the retrotracheal nodule originated from the thyroid. The histopathological diagnosis was adenomatous goiter without malignancy.

Retrotracheal goiters are usually located in the posterior mediastinum, descending posterior to trachea and the recurrent laryngeal nerve. They represent 10%–15% of secondary intrathoracic goiters; the rest are located anterolateral to trachea in the anterior mediastinum (1,2). Retrotracheal goiters usually result from downward displacement of cervical thyroid nodules, arising from the posterior aspects of the thyroid lobes and descending downward to lie in the most posterior aspect of the mediastinum, in front of the vertebral column (1). Their blood supply comes from thyroid arteries. As such, they are considered secondary intrathoracic goiters. In contradistinction, primary intrathoracic goiters arise from ectopic thyroid tissue in the mediastinum, have no connection with cervical thyroid, and receive the blood supply from intrathoracic arteries (1,3). Although an asymptomatic presentation is not uncommon in either secondary or primary intrathoracic goiters, most patients eventually display symptoms associated with compression of trachea, esophagus, or vascular structures.

The patient reported here is very unusual. We are aware of one similar report. This was a patient who had an incomplete encompassment of the cervical trachea by retrotracheal nodule (4). In this report the nodule was observed both by CT and scintigraphy.

Although US is generally very reliable in examining the anatomical location of thyroid tissue, our patient illustrates one of its limitations, which is the inability to extend the examination to behind the trachea. US was useful in our patient in guiding fine-needle aspiration, but in these types of patients CT is required to determine the nature and extent of lesions that appear to extend behind the trachea.