Retrosternal goiter (substernal/intrathoracic goiter) is extension of the cervical thyroid gland into the mediastinum. Retrosternal component is found in 5-20% of all goiters. Most commonly located in the anterior mediastinum but can extend to the posterior mediastinum (10-15%). Four times more common in women, typically diagnosed between ages 50-70. On CT, key diagnostic features are continuity with cervical thyroid, high native density (iodine content, 70-120 HU), prominent and heterogeneous enhancement, and tracheal deviation/compression. I-123 or Tc-99m pertechnetate scintigraphy confirms functional thyroid tissue. Develops on background of multinodular goiter; may be single nodule, dominant nodule, or diffuse enlargement. Surgery (thyroidectomy) is standard treatment — malignancy risk is reported as 3-20%.
Age Range
45-75
Peak Age
60
Gender
Female predominant
Prevalence
Uncommon
Retrosternal goiter usually develops on the background of multinodular goiter — chronic nodular hyperplasia and compensatory hypertrophy of the thyroid gland causes enlargement, and the gland descends through the thoracic inlet into the mediastinum under gravity. Continuity with cervical thyroid is always present — unlike ectopic mediastinal thyroid tissue, vascular supply in retrosternal goiter comes from cervical thyroid arteries (inferior thyroid artery branches). The high iodine content of thyroid tissue explains the high native density on CT (70-120 HU): the high atomic number of iodine atoms (Z=53) dramatically increases X-ray absorption through photoelectric effect — this high density clearly distinguishes thyroid tissue from surrounding soft tissue (30-50 HU) even on non-contrast CT. Prominent enhancement is due to the very rich vascular network of thyroid tissue — superior and inferior thyroid arteries form dense capillary networks and contrast distributes rapidly. Heterogeneous enhancement results from cystic degeneration, hemorrhage, calcification, and fibrotic areas in multinodular structure. Tracheal compression and deviation reflects the mass effect of the lesion. On scintigraphy, Tc-99m pertechnetate or I-123 is actively taken up by the sodium-iodide symporter (NIS) in thyroid tissue — this functional uptake definitively confirms thyroid tissue.
Uninterrupted continuity of the anterior mediastinal mass with the cervical thyroid gland + high native density (70-120 HU) — pathognomonic finding of retrosternal goiter. These two features together provide definitive differentiation from thymoma, lymphoma, and germ cell tumors.
Mass in the anterior mediastinum showing continuity with cervical thyroid, with high native density (70-120 HU). Normal thyroid tissue is significantly denser than muscle (30-50 HU). In multinodular structure, low-density cystic areas, calcifications, and hemorrhagic foci create heterogeneity.
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A mass showing continuity with the cervical thyroid, with high native density (...HU) and heterogeneous structure, is observed in the anterior mediastinum, consistent with retrosternal goiter.
Prominent and heterogeneous enhancement on contrast-enhanced CT — the rich vascular network of thyroid tissue shows intense contrast uptake. Cystic degeneration areas show no enhancement. Solid nodules show variable enhancement. Relationship with major vascular structures should be evaluated given the location near great arteries and veins.
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Prominent and heterogeneous enhancement is observed in the mass on contrast-enhanced series, consistent with thyroid tissue.
Displacement of trachea laterally and/or posteriorly (deviation) and luminal narrowing (compression) by the mass. In severe cases, tracheal diameter may narrow by more than 50%. In bilateral retrosternal extension, trachea may show 'scabbard' (saber-sheath) deformity. Esophageal compression may cause dysphagia.
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The trachea is deviated to the left/right by the mass and the lumen is narrowed to a minimum of ...mm.
Functional thyroid tissue uptake in the mediastinal mass on I-123 or Tc-99m pertechnetate scintigraphy — definitively confirms retrosternal extension. Cold nodules (areas without uptake) should be carefully evaluated for malignancy suspicion. Hot nodules indicate functional autonomous thyroid tissue.
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Radiopharmaceutical uptake is observed in the mediastinal mass on scintigraphy, confirming the diagnosis of retrosternal goiter with functional thyroid tissue.
Various calcification patterns in multinodular goiter: peripheral (eggshell) calcification in benign cystic nodules, coarse calcification in degenerative changes, and punctate microcalcifications raise malignancy suspicion. Multiple calcified nodules support multinodular structure.
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Various calcification patterns (peripheral/coarse/microcalcification) are observed within the mass, consistent with multinodular goiter.
On MRI, multinodular goiter shows heterogeneous signal: solid thyroid tissue intermediate T2 signal, colloidal cystic areas T2 hyperintense, hemorrhagic areas T1 hyperintense with variable T2 signal. MRI is superior in nodule characterization and evaluation of surrounding structure invasion with soft tissue contrast.
Report Sentence
The mass shows heterogeneous signal characteristics on MRI, consistent with multinodular goiter structure.
Criteria
Located in the anterior mediastinum, anterior to the trachea and posterior to the sternum (80-85% of cases). Shows inferior extension from the thyroid lower pole.
Distinct Features
Most common type. Usually removable via cervical approach. Risk of tracheal and SVC compression.
Criteria
Located in the posterior mediastinum, posterior to the trachea and lateral to the esophagus (10-15% of cases). Usually extends to the right because the aortic arch limits left-sided extension.
Distinct Features
Cervical approach may be insufficient, thoracotomy or sternotomy may be needed. Higher risk of recurrent laryngeal nerve injury. Esophageal compression may cause dysphagia.
Criteria
Independent mediastinal thyroid tissue without connection to cervical thyroid. Extremely rare (1%). Results from embryological migration anomaly.
Distinct Features
No continuity with cervical thyroid — most important distinguishing feature on CT. Vascular supply from mediastinal arteries. Confirmed by scintigraphy.
Distinguishing Feature
Thymoma shows no continuity with cervical thyroid, native density is lower than thyroid tissue (40-60 HU vs 70-120 HU), and shows homogeneous enhancement. Retrosternal goiter shows cervical continuity + high native density + heterogeneous enhancement.
Distinguishing Feature
Lymphoma shows low native density (30-50 HU), no continuity with cervical thyroid, and homogeneous moderate enhancement. Retrosternal goiter shows high native density (70-120 HU) and cervical continuity. B symptoms are common in lymphoma.
Distinguishing Feature
Teratoma is a heterogeneous mass containing fat density (-20 to -100 HU) + calcification + fluid — fat component is pathognomonic. Retrosternal goiter shows no fat density and shows continuity with cervical thyroid.
Distinguishing Feature
Multinodular goiter without retrosternal extension remains entirely cervical. Retrosternal goiter is the thoracic extension of the same disease — differentiation is based on location, pathology is the same.
Urgency
urgentManagement
surgicalBiopsy
Not NeededFollow-up
specialist-referralRetrosternal goiter requires surgical treatment (thyroidectomy) — cervical approach is sufficient in most cases (80-90%), posterior extension or large masses may require sternotomy/thoracotomy. Surgical indications: tracheal compression (stridor, dyspnea), esophageal compression (dysphagia), SVC syndrome, malignancy suspicion (cold nodule, rapid growth), and cosmetic. Malignancy risk is reported as 3-20% — FNA of retrosternal nodules may be difficult to access. Preoperative CT is critical for surgical planning: vascular anatomy (aberrant artery), tracheal deviation, posterior extension, and intrathoracic size are evaluated. Thyroid function tests (TSH, fT4) should be checked — hyperthyroidism must be treated before surgery (thyroid storm risk).
Surgical treatment (thyroidectomy) is performed for symptomatic retrosternal goiter. Dyspnea and stridor may develop due to tracheal compression. There is a risk of thyrotoxicosis after iodinated contrast administration (Jod-Basedow phenomenon). Tracheal diameter should be assessed preoperatively.