Ectopic Thyroid in the Anterior Mediastinum Resected Through a Video-Assisted Transcervical Approach: Case Report
Introduction
The most frequent tumors in the anterior mediastinum are thymomas/thymic
lesions (40%), lymphomas (25%), and germ cell tumors (20%). Substernal or
retrosternal goiters/ectopic thyroid comprise 15% of anterior mediastinal
masses (1).
Ectopic thyroid is a rare entity with an estimated prevalence of 1:100,000-300,000
(2) and 1:4,000-8,000 in patients with thyroid diseases (2). Ectopic thyroid
tissue (ETT) can coexist with an orthotopic thyroid, although in the majority
of the cases it is the sole existing thyroid tissue (1). Lingual thyroid is the
most frequent type, corresponding to 47% to 90% of the reported cases (3, 4).
ETT in the mediastinum comprises 1% of all cases (3, 5). In autopsy series, its
incidence is reported to be 7% to 10% (5). Thullier and colleagues, in 2012,
mentioned that only 7 cases had been described in the literature during the previous
30 years (4).
Surgical approaches used for resection of mediastinal ETT are median
sternotomy, posterolateral thoracotomy, video thoracoscopy, robotic surgery, and
transcervical and subxiphoid approaches. Localization in the mediastinum and
size are important features to decide the surgical approach.
Herein, the authors report a case of an ectopic thyroid in the anterior
mediastinum—initially judged to be a small thymoma—that was resected through a
video-assisted transcervical approach.
Case Report
A 58-year-old woman sought medical treatment because of abdominal pain.
Previously, she had been diagnosed with colonic diverticular disease. At the
emergency department, an abdominal computed tomography (CT) was performed and
no abdominal abnormality was seen. A 6 mm pulmonary nodule was detected in the
left inferior lobe and a follow-up chest CT revealed an anterior mediastinum density
below the level of the aortic arch, measuring 24 x 12 mm and showing high
contrast enhancement (Figure 1). Lymphadenopathy, thymoma, ectopic thyroid, and
parathyroid adenoma were the diagnostic hypotheses in the radiology department.
The patient was aware of bearing a nontoxic multinodular goiter and had sought
consultation with two head and neck surgeons. Thyroid hormones levels were in
the normal range (TSH: 1.29 mcUI/ml, normal range: 0.4-4.3 mcUI/ml; free T4: 1.0
ng/dl, normal range: 0.7-1.9 ng/dl). Thyroid ultrasound with Doppler showed a
multinodular goiter with no signs of malignancy. One nodule in the right lobe
underwent fine needle aspiration and was benign (Class II, Bethesda). Thyroid
surgery was not considered by the two consulting surgeons at that time.
The patient reported muscle weakness, but myasthenia gravis was not present. Anti-acetylcholine receptor antibody detection was negative (0.23 nmmol/L; reference: negative < 0.45 nmol/L, positive > 0.45 nmol/L). Electroneuromyography was also negative for myasthenia gravis. Thyroid scintigraphy was not performed, as the patient had undergone CT scan with iodine contrast and nuclear imaging could not be done for at least four weeks. In addition, the main consideration was a small thymoma, and surgery for diagnosis and treatment had been decided.
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