Benign Cystic Mediastinal Lesions

Benign mediastinal cysts are uncommon lesions overall but comprise the third most frequent group of masses in the mediastinum (10-15%). In general, these cysts can be divided into two categories: those that are congenital and those that are acquired. Congenital cysts are the result of abnormal development during embryogenesis, while acquired ones are associated with inflammatory or degenerative processes. Unless the cysts reach a large size and compress adjacent structures, they usually remain asymptomatic and are often only discovered upon imaging investigations for other conditions. Benign mediastinal cysts need to be distinguished from tumors showing cystic changes which is a common phenomenon among mediastinal neoplasms, particularly among thymic epithelial tumors, germ cell tumors, and lymphomas. Therefore, the nature of a cystic mediastinal lesion is generally not evident from clinical and radiological investigations alone and definitive diagnosis usually requires surgical resection. In this context, detailed macroscopic examination and sufficient sampling becomes an important parameter in the pathologic processing of such cases.