Cosimo Sperti, Claudio Pasquali, Andrea Ferronato, Domenico Decet, Franca Chierichetti, Guido Liessi, Sergio Pedrazzoli, Clinica Chirurgica IV, Padova, Italy, Dept. of Nuclear Medicine, Ospedale Civi, Castelfranco Veneto, Italy, Dept. of Radiology, Ospedale Civile, Castelfranco Veneto, Italy

The preoperative differential diagnosis of pancreatic cystic lesions remains difficult. The most important problem is to identify malignant or premalignant lesions that require resection. We previously reported that 18-FDG PET was useful to discriminate malignant from benign cystic lesions in 56 patients (Ann Surg 2001; 134:675-80). Aim of this study was to confirm the reliability of 18-FDG PET in distinguishing benign from malignant cystic lesions in a large cohort of patients. Materials and Methods. From February 2000 to June 2003 further 50 patients with suspected cystic neoplasms (n=33) or intraductal papillary mucinous tumors (IPMT n=17) were prospectively investigated with 18-FDG PET, abdominal computed tomography (CT), serum CA 19-9 assay, and, in some instances, with magnetic resonance imaging. The validation of diagnosis was based on pathologic findings after surgery (n=33), percutaneous biopsy (n=3), and according to follow-up in 14 patients (follow-up range from 1 to 3 years). The 18-FDG PET was analyzed visually and semi quantitatively using the standard uptake value (SUV). Positivity was assumed when a focal uptake occurred with a SUV of at least 2.5. The accuracy of 18-FDG PET and CT was determined for differential diagnosis between benign and malignant cystic lesions. Results. Seventeen patients had malignant tumors; 16 patients (94%) showed 18-FDG uptake with a standard uptake value ranging from 2.5 to 7.0, including two patients with carcinoma in situ. Eleven patients (65%) were correctly identified as having malignancy by computed tomography. Thirty patients had benign tumors: two patients showed increased 18- FDG uptake of 2.6 and 3.0 (a partially intrasplenic pseudocyst and a pancreatic localization of Tangier's disease, respectively). Four patients with benign cystic tumors showed CT findings of malignancy. Sensitivity, specificity, positive and negative predictive values, and efficiency for 18-FDG PET and CT scanning in detecting malignant tumors were 94%, 94%, 89%, 97%, 94%, and 65%, 88%, 73%, 83%, and 80%, respectively. Conclusions: 18-FDG PET is accurate in identifyng malignant pancreatic cystic lesionss and should be routinely used in combination with CT in the preoperative evaluation of patients with cystic lesions of the pancreas.