Detection of nodular pulmonary amyloid by PET positive scan--deception for lung cancer.

Amyloidosis results from proteins being deposited as insoluble β-pleated sheets and disrupting organ function. Each precursor protein induces a separate spectrum of organ involvement, and different disease manifestations within the lung. Although autopsy findings often demonstrate amyloid deposits in various compartments of the lung, few are manifested pathologically. Amyloid lung nodules with positron emission tomography (PET) uptake are rare. We describe a rare case where PET uptake was detected in a pulmonary amyloid nodule. To our knowledge there are six previously reported cases in the English literature. This review also focuses on amyloid derived from immunoglobulin light-chain protein (AL disease), which most frequently involves the lung in both systemic and localized forms of the disease. Manifestations of AL-related lung disease range from nodules identified on incidental chest films to diffuse alveolar and septal deposition mimicking malignancy and or diffuse alveolar damage.