Nodular Pulmonary Amyloidosis Preceding Gastric Mucosa-associated Lymphoid Tissue Lymphoma, Initially Suspected to Be Lung Cancer.

Nodular pulmonary amyloidosis, a subtype of pulmonary amyloidosis, is a unique disease that can mimic lung cancer on radiographic imaging and is related to lymphoproliferative disorders. In this report, we describe a case of a 76-year-old male who presented with a solitary nodule in his left lower lung lobe on computed tomography that increased from 6 mm to 13 mm in diameter over 40 months. Lung cancer was suspected; however, transbronchial lung biopsy revealed deposition of an eosinophilic and homogeneous amorphous substance, which showed apple-green birefringence under polarized light after Congo red staining, and immunohistochemistry analysis returned positive results for immunoglobulin lambda light-chain. Upper gastrointestinal endoscopy revealed a gastric mucosa-associated lymphoid tissue (MALT) lymphoma. These findings indicated that this was a case of nodular pulmonary amyloidosis that preceded a diagnosis of MALT lymphoma.