Can Ahmet S., Nagalli Shivaraj
Ocean University Medical Center
Yuma Regional Medical Center
An enlarged thyroid gland is referred to as a goiter. The thyroid gland is surrounded by thin muscles, subcutaneous fat, and skin and experiences minimal resistance as it grows, typically expanding anteriorly or laterally. When enlarged, the thyroid gland is usually visible and easily palpable; however, detection may be complicated by body habitus. If the thyroid gland grows inferiorly, passing through the thoracic inlet into the thoracic cavity, or if ectopic thyroid tissue is present in the mediastinum, it is referred to as a "substernal goiter." According to the American Thyroid Association, clinical criteria define a substernal goiter as the presence of a retrosternal portion of the thyroid gland observed during a cervical examination without hyperextension. Substernal goiter is also known by various names, including retrosternal goiter, cervicomediastinal goiter, mediastinal goiter, aberrant goiter, mediastinal aberrant goiter, mobile goiter, plunging goiter, wandering goiter, spring goiter, retroclavicular goiter, and intrathoracic goiter. In addition, while various definitions of "substernal goiter" exist, this activity will adhere to the definition provided above. Substernal goiters are classified into primary and secondary mediastinal goiters. Primary mediastinal goiters originate from an ectopic location unrelated to the normal thyroid gland, while secondary mediastinal goiters descend from a primary cervical location. Secondary mediastinal goiters account for 98% of cases, with ectopic thyroid tissue in the chest causing de novo substernal goiter being rare, representing only 2% of all substernal goiters. Substernal goiter may involve one or both thyroid lobes and can cause tracheal deviation or compression and, less commonly, compression of the esophagus or venous structures. Tracheal compression has been reported in 35% to 73% of substernal goiters. Approximately 10% of substernal goiters are located in the posterior mediastinum, with 90% of these being right-sided due to anatomical constraints from the left-sided subclavian arteries and the aortic arch, which limit left-sided expansion. Some studies define substernal goiter as any portion of the thyroid gland that extends through the thoracic inlet, whereas others require that 50% or more of the thyroid be located below the thoracic inlet. This difference in definition contributes to the variability in results among studies. If the lower tip of the thyroid moves above the thoracic inlet when the patient extends their neck, the abnormality is considered positional and does not qualify as a substernal goiter.
甲状腺肿大被称为甲状腺肿。甲状腺被薄肌肉、皮下脂肪和皮肤所包围，在其生长过程中受到的阻力最小，通常向前或向侧面扩张。甲状腺肿大时通常可见且易于触摸到；然而，身体体型可能会使检测变得复杂。如果甲状腺向下生长，穿过胸廓入口进入胸腔，或者纵隔中存在异位甲状腺组织，则称为“胸骨后甲状腺肿”。根据美国甲状腺协会的定义，临床标准将胸骨后甲状腺肿定义为在颈部检查时无需过度伸展就能观察到甲状腺的胸骨后部分。胸骨后甲状腺肿还有各种不同的名称，包括胸骨后甲状腺肿、颈纵隔甲状腺肿、纵隔甲状腺肿、异位甲状腺肿、纵隔异位甲状腺肿、可移动甲状腺肿、坠入性甲状腺肿、游走性甲状腺肿、弹簧状甲状腺肿、锁骨后甲状腺肿和胸内甲状腺肿。此外，虽然存在“胸骨后甲状腺肿”的各种定义，但本活动将遵循上述定义。胸骨后甲状腺肿分为原发性和继发性纵隔甲状腺肿。原发性纵隔甲状腺肿起源于与正常甲状腺无关的异位位置，而继发性纵隔甲状腺肿则从原发性颈部位置向下延伸。继发性纵隔甲状腺肿占病例的98%，胸部异位甲状腺组织导致的原发性胸骨后甲状腺肿很少见，仅占所有胸骨后甲状腺肿的2%。胸骨后甲状腺肿可能累及一个或两个甲状腺叶，可导致气管移位或受压，较少见的是压迫食管或静脉结构。据报道，35%至73%的胸骨后甲状腺肿会出现气管受压。大约10%的胸骨后甲状腺肿位于后纵隔，其中90%位于右侧，这是由于左侧锁骨下动脉和主动脉弓的解剖限制，限制了左侧的扩展。一些研究将胸骨后甲状腺肿定义为甲状腺延伸穿过胸廓入口的任何部分，而另一些研究则要求甲状腺的50%或更多位于胸廓入口下方。这种定义上差异导致了各研究结果的差异。如果患者伸展颈部时甲状腺的下端移至胸廓入口上方，则该异常被认为是位置性的，不符合胸骨后甲状腺肿的标准。
