Lung amyloid nodule detected by 99mTc-aprotinin scintigraphy

We present a case in which an amyloid lung nodule was diagnosed preoperatively by amyloid scintigraphy 99m Tc-aprotinin. A 65-year-old man complained of marked weight loss (9 kg) over a period of 6 months. An abnormal shadow in the middle field of the right lung was detected on chest X-ray, corresponding to a 16-mm nodule in the right middle lobe on thoracic computed tomography (CT). Total protein and immunoglobulin G levels were elevated to 8.3 and 2245 mg/dl, respectively, but other blood tests including several tumor marker levels and Cryptococcus antibodies were all within normal range. Fluorodeoxyglucose positron emission tomography showed no uptake by the lung nodule, so lung amyloidosis was considered as differential diagnosis. To avoid risk of bleeding on bronchoscopy, noninvasive amyloid scintigraphy using 99m Tc-aprotinin was first performed. A nodular, abnormal accumulation was observed in the right middle lung lobe. Diagnostic imaging strongly suggested amyloidosis, so video-assisted thoracic surgery was performed rather than bronchoscopy. Pathological samples showed positive staining with Congo red, and A-λ amyloidosis was diagnosed on the basis of immunostaining. Scintigraphy using 99m Tc-aprotinin offers a useful, noninvasive method for assessing lung amyloidosis.