Sarcoid-like reaction mimics progression of disease after induction chemotherapy for lung cancer.

The use of 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) for staging nonsmall cell lung cancer is widely recognized, whereas the value of fluorodeoxyglucose-positron emission tomography imaging in the evaluation of response to induction chemotherapy is still controversial. We describe a case of a 57-year-old man who had a sarcoid-like reaction develop during induction chemotherapy for a pathologically proven N2 lung cancer. Re-evaluation of the nodal status using fluorodeoxyglucose-positron emission tomography showed false-positive accumulation in the mediastinal and hilar lymph nodes, which led us to suspect lung cancer progression after induction chemotherapy.