Tumefactive Pulmonary amyloidosis in an elderly male: A Diagnostic Dilemma

Abstract Introduction/Objective Tumefactive pulmonary amyloidosis is a rare variant of pulmonary amyloidosis characterized by the extracellular deposition of abnormal protein fibrils in the lung parenchyma, forming tumor-like masses called amyloidomas. Although most cases are clinically silent, it may present with findings that mimic a wide range of respiratory conditions (eg. primary or metastatic malignant nodules, granulomatous disease, multiple pulmonary hamartomas etc), thereby necessitating a comprehensive and broad-based approach to differential diagnosis. Methods/Case Report We present a case of an 88-year-old male with a history of smoking and multiple comorbidities. He presented with numerous bilateral pulmonary nodules identified on a CT scan, concerning for malignancy. A biopsy from a left upper lobe lesion revealed necrotic tissue and was non-diagnostic. A PET scan to assess for metastatic disease was unremarkable, and demonstrated mild hypermetabolic activity, confined to the lungs, with standardized uptake values (SUV) ranging from 4.3 to a maximum SUV of 8.9. A subsequent right lung biopsy was positive for amyloid, confirmed by Congo red staining. A Mass spectrometry analysis further identified the amyloid as AL type. Serum, and urine protein electrophoresis with immunofixation were negative for M protein and the serum free light chain assay was normal as well. Significantly, the bone marrow biopsy also yielded normal results, and the patient was diagnosed with a localized form of AL amyloidosis. Results (if a Case Study enter NA) NA Conclusion This case highlights how tumefactive pulmonary amyloidosis poses a diagnostic challenge due to its rarity and resemblance to malignancy on imaging. Careful histopathological examination, including immunohistochemical stains and amyloid typing, was pivotal in establishing the correct diagnosis and underscores the essential role of pathology and laboratory medicine in differentiating rare pulmonary conditions, along with the need for a multidisciplinary approach in complex diagnostic scenarios.