Gallbladder metastasis from malignant melanoma: diagnosis with FDG PET/CT

Melanoma with metastasis to the gallbladder is sometimes seen on autopsy but is rarely seen in living patients, in part because it is often asymptomatic. A 67-year-old man with a history of malignant melanoma in situ underwent an F-18 FDG PET/CT scan, which showed a gallbladder focus (SUV 16.9). Four months later, on the repeat FDG PET/CT scan, a new lesion in the gallbladder was noted. Laparoscopic cholecystectomy was done and histopathologic findings were consistent with gallbladder metastasis of melanoma. PET/CT detects metastasis at unusual sites accurately and is helpful in correct staging and management of patients with melanoma.