18F-FDG and 11C-MET positron emission tomography findings of cutaneous mast cell tumor in a dog

Abstract

A 12-year-old intact male Maltese dog presented with an inguinal mass. Histopathology revealed a grade III mast cell tumor. Computed tomography demonstrated pulmonary and inguinal nodules and masses. Chemotherapy was performed using a vinblastine/ prednisone protocol, and the inguinal mass disappeared 5 weeks later. Use of 2-deoxy-2-[18F]fluoro-D-glucose (18F-FDG) and L-[methyl- 11C]methionine (11C-MET)-positron emission tomography (PET) demonstrated hypermetabolic areas in the lungs and inguinal region one week after initial chemotherapy. The standardized uptake values of 18F-FDG were not different between lung and inguinal lesions; however, the inguinal lesion had a higher 11C-MET standardized uptake value than the lung lesions. The hypermetabolic area was still visible on the second 18F-FDG-PET scan despite the disappearance of the mass. This is the first report of 11C-MET-PET findings associated with a cutaneous mast cell tumor in a dog.