Abstract
Background Rosai-Dorfman disease is a histiocytic lesion that affects lung rarely. Case presentation We present a 52-year-old female diagnosed with right intrabronchial mass invading the bronchial wall and the extrabronchial tissues with lymphadenopathy. Multiple bronchoscopic biopsies were not diagnostic. Pneumonectomy was performed and postoperative histology revealed marked mucin impaction and bronchial dilatation. The pulmonary tissue showed areas of hemorrhage and chronic inflammation. The mass exhibited an excessive number of lymphocytes, plasma cells, and numerous histiocytes engulfing them (lymphocytophagocytosis). These histiocytes were S100 protein and CD68 positive. These features are consistent with Rosai-Dorfman disease. Conclusion Rosai-Dorfman Disease with pulmonary affection can be misdiagnosed as malignancy. Careful histological examination of the specimen for emperipolesis or lymphocytophagocytosis together with S100 protein and CD68 positivity are the clue for proper diagnosis.