Signet ring gallbladder carcinoma is a rare aggressive variant of mucinous adenocarcinoma with poor prognosis. Positron emission tomography /computed tomography (PET/CT) with Fluor18deoxyglucose (F18-FDG) is a useful tool in the staging of gallbladder cancer. We report a 68 years old man with a surgically resected acute cholecystitis, whose biopsy was positive for signet ring cell gallbladder carcinoma. During surgery, locoregional lymph nodes, liver or peritoneal involvement were not detected. A PET/CT was performed for staging, finding multiple hypermetabolic lytic bone lesions. Percutaneous biopsy of a pelvis bone lesion, confirmed a metastasis of the tumor. In this case, the staging with PET/CT allowed the diagnosis of unsuspected bone metastases and was a useful tool for deciding the best site of biopsy for histologic confirmation.Signet ring gallbladder carcinoma is a rare aggressive variant of mucinous adenocarcinoma with poor prognosis. Positron emission tomography /computed tomography (PET/CT) with Fluor18deoxyglucose (F18-FDG) is a useful tool in the staging of gallbladder cancer. We report a 68 years old man with a surgically resected acute cholecystitis, whose biopsy was positive for signet ring cell gallbladder carcinoma. During surgery, locoregional lymph nodes, liver or peritoneal involvement were not detected. A PET/CT was performed for staging, finding multiple hypermetabolic lytic bone lesions. Percutaneous biopsy of a pelvis bone lesion, confirmed a metastasis of the tumor. In this case, the staging with PET/CT allowed the diagnosis of unsuspected bone metastases and was a useful tool for deciding the best site of biopsy for histologic confirmation.