High prevalence of estrogen and progesterone receptor expression in mediastinal cysts situated in the posterior mediastinum.

BACKGROUND To identify and estimate the prevalence of mediastinal cysts lined by the epithelium expressing steroid receptors. METHODS We retrieved 19 mediastinal cysts from our pathology files from 1996 to 2004, and examined estrogen receptor (ER) and progesterone receptor (PR) expressions in the cysts. RESULTS Three paravertebral cysts, all in women, one bronchogenic cyst in a woman, nine thymic cysts, and six pericardial cysts were found in the pathology files. Paravertebral cysts were situated in the posterior mediastinum and were attached either to the left or the right of the vertebral column. All cysts were radiologically diagnosed before surgery as neurogenic tumors. They were excised by video-assisted thoracoscopic surgery. The epithelial lining of the cyst in all three cases was strongly positive for both ER and PR. A thymic cyst in one woman was weakly positive only for the ER. In all other cases, the lining was entirely negative for both ER and PR. CONCLUSIONS Posterior mediastinal paravertebral cysts characteristically express ER and PR. They should be recognized as a distinct type of mediastinal cyst because they are biologically different from bronchogenic cysts, seem not to be infrequent, and sometimes are misdiagnosed as a neurogenic tumor.