Solitary Pulmonary Hyalinizing Granuloma Combined with Primary Lung Adenocarcinoma: Case Report

Pulmonary hyalinizing granuloma (PHG) is an extremely rare benign mass-forming fibrosclerotic lesion of the lung with unknown etiology. Although PHG mimics malignancies in clinical and radiological examinations, concurrence with primary lung carcinoma has never been reported. A 67-year-old asymptomatic man was presented with a pulmonary nodule incidentally detected during follow-up for retroperitoneal fibrosis. Chest CT confirmed a 1.5-cm solitary subpleural nodule in the upper left lung without lymphadenopathy. Fluorodeoxyglucose positron emission tomography (FDG-PET) indicated low uptake of FDG (maximum standardized uptake value, 3.0) in the same site, and the patient underwent wedge resection with suspected primary lung cancer. Intraoperative frozen section biopsy of the lesion revealed histopathological features of PHG without malignancy, and no additional surgical treatments were considered necessary; the operation was completed at this point. However, postoperative thorough examination of permanent sections from the resected specimen revealed a concurrent adenocarcinoma component, sized 0.6 cm, which was forming a composite tumor with PHG; the patient subsequently underwent a second surgery including a completion left upper lobectomy and regional lymph node dissection. The rarity of disease and the unknown etiological connection between PHG and co-existing carcinomas may cause a diagnostic pitfall and obscure clinical treatment strategies for patients. Diagnosis of PHG in small biopsy samples should be made with caution, especially when diagnosed by intraoperative consultation (frozen section) aimed to exclude malignancies.