Endosonography and elastography in the diagnosis of pancreatic neuroendocrine tumors

Summary: Introduction: The group of neuroendocrine tumors derived from pancreatic cells is called pancreatic neuroendocrine tumors (PNETs). The combination of EUS and elastography (EG) expands diagnostic and imaging capabilities. Aim: The aim of our work was to determine the representative images of B-mode for PNET, evaluation of a typical EG image of PNETs, use of strain ratio (SR) and “strain histogram” (SH) in differential diagnosis of PNETs, determination of SR and SH cut off value for PNETs and comparison of standardized measurements with literature. Methods: Patients examined at the Internal Gastroenterology Clinic were included in the cohort. A total of 31 patients were examined. The group included 25 patients (8 men, 17 women). The mean age in group was 52.76 years (14–74). Non-invasive examination by endoscopic ultrasonography was performed on all patients. After locating the lesion by ultrasound, the first recording was made after freezing the image in B-mode and performing size measurement. Subsequently, a Strain elastography measurement was performed. In the monitored group we recorded an average size of 12.75 mm. Results: The characteristics of the image in B-mode were as follows for PNETs 68% hypoechogenic, 12% hyperechogenic, 12% isoechogenic and 8% mixed echogenicity. 80% of PNETs in B-mode were sharply demarcated and 20% with blurred borders. The accuracy of the value assignment typical of pancreatic malignancies using elastography was 96% for PNET in 5-degree classification system and 88% for a 4-degree classification, for SR cut off >3.2 with a sensitivity of 80% and SH cut off <50 100%. Discussion: Given the average tumor sizes observed in our study, EUS provides high sensitivity in PNET diagnostics and allows diagnostics at a time when minimally invasive removal is still possible. In addition to the typical picture of hypoechogenicity and the less frequently described pictures of hyperechogenicity and isoechogenicity for PNET, we also observed mixed echogenicity. The elastographic qualitative strain image evaluated by the four- and five- -degree classification proved to be reliable in distinguishing PNET from benign tumors. In quantitative elastography, the values of SR are between malignant and benign deposits of the pancreas, one of the reasons for such values may be the diversity of this group of diseases with different mitotic activity – grade of the tumor. Conclusion: Consistency of the results published by us, shows the applicability of this method in deciding on a definitive diagnosis if tumor histology is not and cannot be available. Key words: neuroendocrine tumor – pancreas – ultrasonography – elastography