Anterior mediastinal masses and thymic cysts

Abstract

Cystic lesions of the anterior mediastinum in children suggest a well-known group of benign lesions that are comparatively frequent. Thymic cysts (TCs) are mostly positioned in the anterior mediastinum and some patients in the neck. Benign TCs classified as congenital intra-thoracic mesothelial cysts are commonly asymptomatic and have slight clinical significance. Multilocular TC, which can mimic another anterior mediastinal cystic tumor and is seen in adults, is more clinically important. It is a sporadic mediastinal lesion thought to arise in the course of acquired inflammation. Congenital mediastinal cysts represent 3%-6% of all mediastinal tumors and 10%-18% of radiologically reported mediastinal masses. Mediastinal TCs are uncommon and it is hard to know their true incidence. About 60% of cases with mediastinal TCs are asymptomatic, and the remainder of patients complains of nonspecific symptoms (e.g., chest pain, dyspnea, or cough). The literature suggests that most cysts are benign, but an indefinite percentage may have a neoplastic process and result in significant compressive symptoms over time. Clinical symptoms of TCs vary depending on the location. In addition, frequent symptoms at the appearance of enlarged benign thymic and mediastinal cysts generally contain compressive symptoms (e.g., respiratory distress, thymic pain, and symptoms related to Horner syndrome, hoarseness, dysphonia, dyspnea, orthopnea, wheezing, and fever). Many TCs have cystic density and a neat border and are simple to diagnose with radiological imaging. However, some TCs are hard to identify before surgery and may be misidentified as thymomas depending on their site and computed tomography results. Excision by thoracotomy, median sternotomy, or video-assisted techniques is essential for conclusive diagnosis, management, and abolition of relapse of anterior mediastinal masses and TCs. Histopathologic examination may be required after surgery. Considering the extent of the mass and the preliminary inability to make a definitive diagnosis, en bloc excision of the cyst was thought to be preferred to circumvent likely complications (e.g., perforation, spillage of the contents, or incomplete excision).

Keywords: Mediastinal mass; Thymic cyst; Malignant tumor; Cysts; Thymoma; Computer tomography

Core Tip: Since thymic cysts may show malignant transformation, they pose a diagnostic challenge requiring only surgical excision and histologic examination. Because of cystic changes that mask tumoral features, extensive sampling is necessary to avoid missing a malignancy.