Recurrence of sarcoidosis accompanied by lung cancer after drug‐induced pulmonary sarcoidosis with lung injury

Abstract Sarcoidosis is a multisystemic granulomatous disease that is frequently localized in the lungs and lymph nodes. We herein report a case of pulmonary sarcoidosis secondary to shin'iseihaito administration. During remission with 5 mg prednisolone/day of maintenance treatment, chest computed tomography revealed a mass in the left lower lobe with re‐enlarged bilateral hilar/mediastinal lymph nodes. Transbronchial lung biopsy of the mass and endobronchial ultrasound‐guided transbronchial needle aspiration of mediastinal lymph nodes revealed adenocarcinoma and noncaseating granulomas, respectively. Based on these findings, the patient was diagnosed with sarcoidosis recurrence associated with lung cancer without cancer metastasis. We present the case of sarcoidosis recurrence associated with lung cancer after drug‐induced pulmonary sarcoidosis with lung injury. To our knowledge, this is the first report of sarcoidosis triggered by drug administration and lung cancer. Histological diagnosis of mediastinal lymphadenopathy with lung cancer is essential for differentiating metastasis from sarcoidosis.