A40-05 Pulmonary Amyloidosis Beyond the Interstitium: Nodular and Pleural Forms Mimicking Malignancy

Abstract Purpose Pulmonary amyloidosis is a rare manifestation of amyloid deposition within the thorax and can present with diverse radiologic and clinical findings that mimic malignancy or chronic infection. Recognition of these variants is crucial to avoid misdiagnosis and to guide appropriate systemic evaluation. We present three cases demonstrating nodular, cystic, and pleural patterns of biopsy-proven pulmonary amyloidosis, highlighting diagnostic challenges and multidisciplinary management strategies. Methods We retrospectively reviewed three male patients, aged 77-84 years, with histopathologic confirmation of pulmonary amyloidosis evaluated at our tertiary care center. Clinical data, radiologic features, histopathology, and systemic evaluation were analyzed. All diagnoses were confirmed by Congo red staining with apple-green birefringence under polarized light, and light-chain typing was performed when available. Results Case 1: An 84-year-old man undergoing surveillance for bilateral upper-lobe nodules developed multiple septated cystic lesions with soft-tissue irregularities in the right lower lobe. PET imaging showed a hypermetabolic cystic lesion concerning for malignancy. CT-guided biopsy revealed apple-green birefringence on Congo-red staining, confirming pulmonary amyloidosis. Liquid chromatography tandem mass spectrometry identified lambda (AL type) amyloid deposition. The patient had a 30-pack-year smoking history and occupational exposures as a Navy veteran and professional painter. Case 2: A 78-year-old man with known systemic amyloidosis involving kidneys, lungs, and heart, attributed to Agent Orange exposure, was admitted for progressive dyspnea. Imaging revealed recurrent bilateral pleural effusions refractory to diuretics. Serial thoracenteses showed pseudo-exudative fluid negative for infection or malignancy. Recurrent effusions were managed with planned PleurX catheter placement for long-term palliation. Case 3: A 77-year-old man with COPD and prior Agent Orange exposure demonstrated interval growth of a right lower-lobe nodule. Biopsy excluded malignancy but showed amorphous eosinophilic deposits consistent with amyloidosis. The patient was clinically stable on surveillance. Conclusion Pulmonary amyloidosis exhibits a broad radiologic and clinical spectrum, including nodular, cystic, and pleural forms. These cases underscore the importance of radiologic-pathologic correlation in distinguishing amyloidosis from malignancy, especially in patients with environmental or occupational exposures. Multidisciplinary evaluation with pathology, radiology, and hematology collaboration enables accurate diagnosis, prevents unnecessary interventions, and guides appropriate systemic work-up and longitudinal monitoring. This abstract is funded by: None