Sarcoidosis development during induction chemotherapy for lung cancer mimicked progressive disease

We report a rare case of sarcoidosis that developed during induction chemotherapy for primary lung cancer, mimicking progressive disease. A 63-year-old man had an abnormal shadow in the right upper lung, and a bronchoscopic examination revealed a squamous cell carcinoma. Swelling of a pretracheal lymph node was also noted. Thus, we gave induction chemotherapy consisting of paclitaxel (days 1, 8) + carboplatin (days 1, 8) for two cycles under clinical staging of T2N2M0. After induction chemotherapy, (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) showed positive accumulation of FDG in mediastinal and bilateral hilar lymph nodes that had been negative in a previous FDG-PET examination, which led us to suspect disease progression. Transbronchial lymph node biopsy results showed sarcoid granulomas in the specimens. Following complete resection of the lung cancer, sarcoid granulomas were revealed in both nonneoplastic lung tissue and lymph nodes, which resulted in a diagnosis of lung cancer accompanied with sarcoidosis.