Multilocular mediastinal cyst with rim calcification: report of a case.

We report a case of a multilocular anterior mediastinal cyst with rim calcification and severe adhesion to the adjacent organs. We excised the cyst completely, with resection of the left phrenic nerve, pericardium, and left lung because of the severe adhesion. Histological examination revealed that the multilocular cystic walls were composed of fibrous connective tissue and calcifications, but the lining epithelial cells were absent because of dystrophic calcification resulting from chronic inflammation. On the basis of the location and pathological findings, we diagnosed a multilocular mediastinal cystic tumor; most likely a multilocular thymic cyst. It is important to distinguish a multilocular thymic cyst from a unilocular thymic cyst because a multilocular thymic cyst may recur postoperatively and coexist with a thymic epithelial tumor. Dense adhesion to the surrounding mediastinal structures may make removal difficult, especially if there is rim calcification.