Improved Detection of Minimal Residual Disease by 11C-Methionine PET/CT in a Young Patient with Unusual Extramedullary Presentation of Recurrent Multiple Myeloma

Extramedullary relapse of multiple myeloma (MM) is uncommon. A 40-year-old woman with history of MM underwent PET/CT using 11 C-methionine (C-MET) after the detection of a vulvar lesion on MRI, biopsy proven to be extramedullary relapse of MM. The vulvar lesion was negative at the 18F-FDG PET/CT but showed high uptake of C-MET; focal uptake of both 18F-FDG and C-MET was shown within the muscles of the left leg, histologically confirmed as extramedullary relapse of MM. 18F-FDG PET/CT performed after chemotherapy showed no uptake in both sites, whereas posttreatment C-MET PET/CT showed persistence of residual uptake within the vulvar lesion.