18F-FDG PET scanning in pulmonary amyloidosis

(18)F-FDG PET plays an important role in the evaluation of patients with lung malignancies but can lead to false-positive and false-negative results. Very little is known about (18)F-FDG PET scanning in amyloidosis.

A computer-assisted search of medical records was conducted to identify subjects with pulmonary amyloidosis (confirmed by biopsy) who were seen at the Mayo Clinic during a 15-y period between January 1, 1997, and December 31, 2011, and had a PET scan available for current review.

Eighteen patients were diagnosed to have amyloidosis by lung biopsy (15 surgical, 2 transthoracic needle, and 1 bronchoscopic). The mean age of the patients was 64.8 y (range, 32-80 y). Seventeen patients had primary amyloidosis, including 5 with Sjögren syndrome, 1 with rheumatoid arthritis, and 1 with multiple myeloma. The most common abnormal findings on the chest CT scan were pulmonary nodules (n = 14), followed by cysts (n = 6) and reticular opacities (n = 4). Eight patients had positive (18)F-FDG PET results (intrathoracic (18)F-FDG uptake), including 4 patients with coexisting mucosa-associated lymphoid tissue lymphoma (maximal standardized uptake value [SUVmax] range, 3.1-6.7) and 1 patient with a pleural plasmacytoma (SUVmax, 7.2); the remaining 3 patients had amyloid only (SUVmax range, 2.1-3.2). Ten patients with negative PET results included 3 additional patients with mucosa-associated lymphoid tissue lymphoma.

Positive (18)F-FDG PET results, especially with an SUVmax of more than 3, in patients with pulmonary amyloidosis should raise suspicion about associated lymphoma or plasmacytoma, but negative PET results do not exclude the presence of such neoplasms.