Solitary nodular pulmonary amyloidosis mimicking primary lung cancer: A case report.

Nodular pulmonary amyloidosis is a rare, localized form of amyloid deposition in the lung and an uncommon cause of solitary pulmonary nodules. Its radiological features may closely mimic that of primary lung cancer if spiculation or fluorodeoxyglucose uptake is present, making preoperative diagnosis challenging. Here, we report the case of a woman in her 60s who was referred to our hospital after an abnormal opacity was detected by routine chest radiograph. Chest computed tomography revealed a 21 mm × 12 mm solid nodule with partial spiculation in the left lower lobe. Fluorodeoxyglucose positron emission tomography/computed tomography demonstrated mild uptake (maximum standardized uptake value; 2.5). Bronchoscopic biopsy results were inconclusive, and diagnostic video-assisted thoracoscopic left basal segmentectomy was performed because malignancy could not be excluded. Histopathological examination under polarized light microscopy demonstrated Congo red-positive amyloid deposition with apple-green birefringence, confirming nodular pulmonary amyloidosis. This case highlights that nodular pulmonary amyloidosis can mimic primary lung cancer on imaging and diagnostic surgical resection may provide definitive diagnosis and local treatment if bronchoscopic biopsy is inconclusive. Long-term follow-up is warranted, considering its reported association with lymphoproliferative disorders.