[Sarcoidosis with right middle lobe atelectasis initially suspected of malignant lymphoma; report of a case].

60-year-old woman was admitted with an abnormal shadow on the chest roentgenogram. Computed tomography showed atelectasis of the right middle lobe and hilar and mediastinal lymphadenopathy. Bronchoscopic examination revealed an obstruction at the orifice of the right middle lobe bronchus and biopsy was performed. The biopsy suggested malignant lymphoma. A diagnosis of methotrexate-associated lymphoproliferative disorders was suspected because the patient was administered methotrexate to treat the rheumatoid arthritis. The video-assisted thoracoscopic surgery was performed. Histological examination showed no malignancy and sarcoidosis in the peribronchial lymph nodes. The compressed middle lobe bronchus by enlarged lymph nodes was consider to be the cause of the middle lobe atelectasis.