Objective To review experience in preoperative detection of islet cell tumors using multislice computed tomography （MSCT） and summarize various imaging features of functioning islet cell tumors on enhanced MSCT.Methods Seventy patients with clinical or pathological diagnosis of functioning pancreatic islet cell tumor between October 2003 and February 2007 were included in this retrospective study. Seventy-four enhanced MSCT scans in these patients were identified. All MSCT scans were interpreted by two experienced radiologists by consensus interpretation. Surgery and pathology reports were used to confirm the diagnosis

localization

and size of tumors.Results Totally

73 functioning islet cell tumors including 65 benign insulinomas

2 benign glucagonomas

3 malignant insulinomas

and 3 malignant glucagonomas were pathologically diagnosed. Tumors in only two cases were not found by MSCT. In 67 benign lesions

32 showed typical enhancement style

21 showed prolonged enhancement in portal venous phase

4 showed delayed enhancement

4 had iso-dense enhancement with normal pancreatic parenchyma

2 had no enhancement at all in arterial phase and portal venous phase

and 4 had inhomogeneous enhancement with necrosis or cyst-formation. Patchy or spotty calcifications were found in 3 of the 67 tumors. In 6 malignant islet cell tumors

vessel invasion （2/6） and bowel invasion （1/6） were seen. Different enhancement patterns were shown. All hepatic metastases showed hyper-enhancement during their arterial phase. ConclusionsPancreatic islet cell tumor may display a wide spectrum of presentations in MSCT. Tumors with unusual appearances often present as diagnostic challenges. Non-contrast and post-contrast multiphase scans are recommended for the localization of functioning islet cell tumors.