Mediastinal Rosai-Dorfman Disease With Widespread Lesions: When Surgical Biopsy Is Needed

Rosai-Dorfman disease (RDD) is a rare benign disorder of the histiocytes, affecting lymph nodes in its classic form. Extranodal RDD is considered the uncommon subtype and potentially impairs all tissues and intrathoracic organs. In our report, a ¹⁸F-fluorodeoxyglucose positron emission tomography scan of a mediastinal mass infiltrating the lungs and of widespread lesions suggested the presence of a metastatic disease. Open thoracic biopsy was required for immunochemistry and histopathology. Mediastinal mass with lesions disseminated throughout the body is an unusual presentation of extranodal RDD that calls for a challenging differential diagnosis to rule out the suspicion of metastatic malignancy.