Mediastinal thymic cysts: a narrative review

Abstract

Background and Objective Mediastinal thymic cysts are a relatively rare pathology. With the expansion of eligible individuals screened with cross-sectional imaging for lung cancer, it is likely that there will be an increase in the number of individuals presenting with these cysts. Understanding this rare pathology will become more important when this incidental pathology is encountered. Methods Search of PubMed was undertaken using keywords “mediastinal”, “mediastinum”, “thymic”, “thymus”, “cyst”. Relevant literature was reviewed and selected for this comprehensive narrative review, including case reports, case series, and retrospective reviews. Key Content and Findings Thymic cysts in the mediastinum can be classified into two broad categories, congenital and inflammatory. Accurate diagnosis by imaging is challenging and the majority of patients are asymptomatic. Literature suggests that the majority of cysts are benign, however an unknown percentage may harbor neoplastic processes and over time can cause significant compressive symptoms. Definitive treatment and diagnosis is surgical, with overall excellent outcomes. The decision to pursue surgical treatment versus surveillance requires a shared decision making approach with patients. Conclusions Given the scarcity of available high quality evidence regarding the management of mediastinal thymic cysts, this review provides practitioners a broad knowledge base to guide patients to make informed decisions.

Benign lesions of the mediastinum

“…Mediastinal cysts are classified into unilocular or multilocular, and congenital or acquired. Most congenital cysts are unilocular, while inflammatory and neoplastic cysts tend to be multilocular 6 …”

“…Thymic cysts are most common in the anterior mediastinum, accounting for 1%–3% of all mediastinal masses 19 . Congenital cysts are rather unilocular, whereas inflammatory cysts that are thought to be derived from a dilatation of Hassall corpuscles tend to be multilocular 6 . Most patients are asymptomatic.…”

“…19 Congenital cysts are rather unilocular, whereas inflammatory cysts that are thought to be derived from a dilatation of Hassall corpuscles tend to be multilocular. 6 Most patients are asymptomatic. Microscopically, thymic tissue with Hassall corpuscles is the key finding.…”

“…Bronchogenic cysts and oesophageal duplication cysts are both developmental malformations arising from the foregut. 6,19 Bronchogenic cysts predominantly occur in the mediastinum, with common locations being carinal, paratracheal, and paraesophageal, although they may also be found intrapulmonary or hilar. Typically presenting as unilocular structures, these cysts are…”

“…Most congenital cysts are unilocular, while inflammatory and neoplastic cysts tend to be multilocular. 6…”