Incidental neuroendocrine tumors of the pancreas: MDCT findings and features of malignancy.
OBJECTIVE
The objective of our study was to evaluate the MDCT features of incidentally detected neuroendocrine tumors (NETs) of the pancreas, identify features that can predict tumor biology or aggressiveness and long-term outcome, and determine the incidence of "nonbenign" behavior.


METHODS
In this retrospective study, 60 histologically verified pancreatic NETs incidentally detected with contrast-enhanced MDCT were included. Various MDCT features such as size, morphology, enhancement, and presence of calcifications were evaluated and were correlated with tumor biology on histopathology. The sensitivity, specificity, predictive values, and accuracy were calculated for MDCT features in predicting nonbenign biology and risk of recurrence.


RESULTS
A total of 32 of 60 (53%) NETs were nonbenign: most were large (mean, 29.1 mm) with a solid or complex pattern. NET size of 3 cm or larger yielded a positive predictive value of 61% for nonbenign tumors and 100% when calcification was present. In 12 patients with recurrence, 92% of NETs were nonbenign. The presence of calcification, local invasion, main pancreatic duct dilatation, vascular invasion, and lymph node enlargement along with angioinvasion and a Ki-67 index greater than 2% on histology were associated with a nonbenign diagnosis and a higher risk of recurrence.


CONCLUSIONS
Approximately 50% of incidental NETs show uncertain or malignant behavior. Solid tumors 3 cm or larger are commonly nonbenign; however, about 30% of tumors smaller than that size cutoff can be malignant. Nonbenign tumors and those with invasive features on MDCT have a higher incidence of recurrence.
Department of Radiology, University Hospital G. B. Rossi, University of Verona, Verona, Italy.
Anna
A
Gallotti
Rocio Perez
RP
Johnston
Pietro A
PA
Bonaffini
Thun
T
Ingkakul
Vikram
V
Deshpande
Carlos
C
Fernández-del Castillo
Dushyant V
DV
Sahani
D000328:Adult; D000368:Aged; D002114:Calcinosis / Q000000981:diagnostic imaging; D003287:Contrast Media; D005260:Female; D006801:Humans; D033162:Incidental Findings; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D018358:Neuroendocrine Tumors / Q000000981:diagnostic imaging* / Q000601:surgery; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery; D011237:Predictive Value of Tests; D011379:Prognosis; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
D003287:Contrast Media