Spread of Goiters outside the thyroid bed - A review of 190 cases and an analysis of the incidence of the various extensions

Objectives: To analyze the distribution of thyroid goiters into the mediastinum and/or behind or along the sides of the pharynx, and to review the anatomy of the spaces in the neck that explains these extensions. Methods: We used a 28-month period, to retrospectively identify 190 cases of neck goiters that underwent computed tomographic imaging. The maximal size of a normal thyroid gland and the limits of the normal thyroid bed were defined on the basis of established anatomic measurements. Standard definitions of the mediastinum and its compartments were also used. Each case was reviewed by 3 radiologists, and extension of the thyroid gland into the mediastinum or cranially behind or along the sides of the pharynx was noted. All cases were correlated with clinical observations. Results: Of the 190 goiters, 106 (55.8%) were confined to the thyroid bed, 70 (36.8%) extended into the mediastinum, and 14 (7.4%) extended behind or along the sides of the pharynx. All 70 cases that extended into the mediastinum involved the anterior mediastinum, and 5 (7.1%) of these extended into the posterior mediastinum. Conclusions: Goiterous extension outside of the thyroid bed occurred in 84 (44.2%) of cases. Although extension cranially behind the pharynx is uncommon, the physician should be aware of this diagnosis and the fascial anatomy that explains its occurrence. All of the goiters that were in the posterior mediastinum also had a component in the anterior mediastinum.