Isolated thymic Rosai-Dorfman disease with mediastinal bronchogenic cyst: a case report

Rosai-Dorfman disease (RDD) is a unique histiocytic proliferative disorder that occurs primarily in lymph nodes or extranodal sites. Isolated mediastinal thymic RDD is rare. Furthermore, the combination of this disease entity with mediastinal bronchogenic cyst is an even rarer phenomenon. A 45-year-old woman presented with two mediastinal masses that was detected using chest radiography. The patient underwent thoracoscopic surgery for the removal of the mediastinal masses. One lesion was diagnosed as thymic RDD. Histologically, a granulomatous lesion characterized with infiltration of lymphocytes, plasma cells, and histiocytes with lymphocytes engulfed in their cytoplasm was indentified. The other was diagnosed as primary mediastinal bronchogenic cyst. To the best of our knowledge, this is the first description of a thymic RDD and a bronchogenic cyst occurring simultaneously in the mediastinum. We discuss the clinical, pathologic findings as well as differential diagnoses.