A 60-year-old man with history of left nephrectomy for clear cell renal cancer (stage I) and resected colorectal adenocarcinoma (stage II) presented with a pulmonary mass lesion in the left upper lobe on surveillance imaging. Transaxial CT (B) revealed a 2.9 cm slightly lobulated lesion in the inferior lingular segment of the left upper lobe overlying the left oblique fissure. 18-F FDG PET/CT images (A, C, D) demonstrated moderate to marked FDG avidity (SUVmax 6.4) in this lesion.\nHistopathology of CT-guided core needle biopsy showed tumour cells with relatively uniform nuclear and clear cell cytoplasm with positive staining for PAX8 and renal cell antigen, consistent with metastatic renal cell carcinoma. The patient underwent wedge resection of the left upper lobe metastasis with clear excisional margins.\n6 months later, follow-up imaging with 18-F FDG PET/CT and diagnostic CT was performed. Transaxial CT (B) demonstrated a slowly enlarging subcentimeter 9mm pulmonary nodule in the right upper lobe. Maximum intensity projection, transaxial fused PET/CT and transaxial PET (A, C, D) images demonstrated moderate FDG avidity (SUVmax 4.6 on current PET, SUVmax 2.4 on previous PET (not shown)) in this lesion. No other suspicious FDG avid focus was detected. Given the proven pulmonary metastatic disease from renal cell cancer, further small volume oligometastatic disease was suspected. Reliable needle biopsy of the lesion was considered difficult due its small size and deep location. The patient subsequently underwent segmental resection of this sub centimeter pulmonary nodule.\nHistopathology of the second pulmonary nodule demonstrated no evidence of malignancy. Instead, there was amorphous hyaline acellular amyloid-like material associated with a rim of multinucleated inflammatory cells (). The chronic inflammatory cells comprised mainly of mature plasma cells with smaller numbers of lymphocytes. Crystal violet stain was positive, and the Congo red stain demonstrated focal birefringence, confirming nodular pulmonary amyloidosis. The patient continues to be under observation for further tumour recurrence.
A 64-year-old male with a history of CKD Stage 3 with 330 mg/day of proteinuria (eGFR by 4-variable MDRD of 52 mL/min/1.73 m2 with a baseline serum creatinine of 1.7 mg/dL), monoclonal gammopathy with elevated kappa light chains on urine protein electrophoresis, and anemia of chronic disease presented over multiple hospitalizations with complaints of peripheral neuropathy, orthostatic hypotension, and unintentional weight loss. The initial investigation included normal levels of vitamin B-12, folate, heavy metals, and was negative for myelin associated glycoprotein antibodies and lyme antibodies. A bone marrow biopsy was completed to rule out progression to multiple myeloma and demonstrated normocellular bone marrow, no clonal plasma cell populations, and an eosinophilic deposit negative for Congo red stain. A 4 mm osteosclerotic lesion was biopsied and demonstrated similar deposits. An abdominal fat-pad biopsy was also negative for Congo red stain. An echocardiogram demonstrated nonspecific findings suggestive of amyloidosis including concentric left and right ventricle hypertrophy, diastolic dysfunction, biatrial enlargement, and tricuspid and mitral valve regurgitation. A renal biopsy was postponed due to concern for a bleeding diathesis as he developed severe right flank ecchymosis after a short coughing bout and subsequently severe thrombocytopenia. A bone marrow biopsy was repeated and amorphous material was suggestive of amyloid deposits but again negative for Congo red stain by two separate pathology laboratories. The patient subsequently developed nonnephrotic range proteinuria of 2.2 gm g/day and acute kidney injury. The acute kidney injury progressed to dialysis-dependent renal failure. During creation of an arteriovenous fistula for dialysis, a segment of the radial artery and brachial vein were submitted for testing and were also negative for Congo red stain. A renal biopsy was performed and was positive for Congo red stain with characteristic apple-green birefringence in the amyloid deposits involving the glomeruli, vessels, and interstitium (). Immunofluorescent histology confirmed kappa light chain deposition and electron microscopy demonstrated amyloid deposits characterized by relatively straight, nonbranching, randomly arranged fibrils. Following the completion of the renal biopsy, a final analysis of the second bone marrow biopsy by a third facility recognized as a center of excellence confirmed the presence of AL- (kappa-) type amyloid by liquid chromatography tandem mass spectrometry of peptides microdissected from the bone marrow specimen. The patient was referred to an outside facility for treatment where he received melphalan and dexamethasone. He did not have an adequate hematologic response to therapy and died eight months after AL-amyloidosis was confirmed by renal biopsy.