Multicentric Castleman's disease developing during follow‐up of sarcoidosis

Pulmonary sarcoidosis is reported to have complication of lymphoproliferative disease such as malignant lymphoma, but the complication of multicentric Castleman's disease (MCD) is rarely reported. In our case of a 60‐year‐old woman, bilateral hilar lymphadenopathy was noted in her chest X‐ray. We performed a transbronchial lung biopsy. She was diagnosed as having pulmonary sarcoidosis (Stage II). The shadow on chest X‐ray disappeared without treatment. However, after 8 years, swelling of the mediastinal and abdominal lymph node, thickened bronchovascular bundle, and multiple nodular shadows were identified, and a thoracoscopic lung biopsy was performed. Based on the histopathological findings and elevated serum interleukin‐6 level (75.7 pg/mL), she was diagnosed with pulmonary sarcoidosis complicated by MCD. When a change in chest X‐ray findings are found during monitoring of pulmonary sarcoidosis, it is important to proceed with a thoracoscopic lung biopsy, because of the possibility of the rare complication of MCD.