Intrathoracic (
substernal) goiter, depending on definition, is seen in up to 45% of all patients operated for
goiter. It can either be primary (
ectopic thyroid tissue detached from a cervical thyroid mass), which is very rare (1%), or (more commonly) secondary, where a portion of the
goiter extends retrosternally. There is no consensus on diagnostic or therapeutic management, partly because many are asymptomatic. Classification involves functional characterization with serum TSH and morphological characterization with diagnostic imaging and cytology to rule out
malignancy, which is not more common than in cervical
goiters. Pulmonary function is often affected in asymptomatic individuals also. Therefore, but also because natural history is continuous growth and evolution from euthyroidism to
hyperthyroidism, most experts recommend
therapy. In primary as well as secondary
intrathoracic goiter, the
therapy of choice is total/near-total
thyroidectomy and subsequent
levothyroxine substitution. Data suggest that complications are only slightly more prevalent than in cervical
goiters. Although
levothyroxine is not recommended for
goiter shrinkage, there is increasing focus on radioactive
iodine as an alternative to surgery in secondary
intrathoracic goiters. Here it can reduce thyroid size by on average 40% after 1 yr and improve respiratory function and quality of life. Recent studies show that
recombinant human TSH, currently used off-label, can augment the radioiodine-related
goiter shrinkage by 30-50%. With currently used doses of
recombinant human TSH, the side effects, besides
hypothyroidism, are rare and mild. Future studies should also explore the use of radioiodine in primary
intrathoracic goiter and compare surgery and radioiodine, head to head.