[A case of pulmonary hyalinizing granuloma with high-grade uptake on FDG-PET mimicking metastatic lung cancer].

A 28-year-old man was referred to Hakodate Municipal Hospital for examination of multiple pulmonary nodules detected on a medical check-up. His chest CT demonstrated well-defined multiple nodules with random distribution. 18-fluorodeoxyglucose positron emission tomography (FDG-PET) showed abnormal uptake in the pulmonary nodules and the hilar, mediastinal lymph node. No other accumulation was observed outside the thorax. Transbronchial lung biopsy did not yield a diagnosis. Based on the high accumulation on FDG-PET, we suspected a malignant tumor and performed right S4 wedge resection under video assisted thoracoscopy. Considering the histologocal and immunohistological findings, we diagnosed pulmonary hyalinizing granuloma. No treatment was given and subsequently stable disease was obtained on chest radiography. The follow-up FDG-PET showed standardized uptake value reduction. Pulmonary hyalinizing granuloma is infrequent and benign, but has been reported to possibly progress to lymphoproliferative disease. Consequently, FDG-PET is valuable to evaluate the activity of the disease itself and the possibility of transition.