Clinical significance of enhanced MRI in differentiating benign and malignant pancreatic neuroendocrine tumors

Abstract

Objective To determine the clinical value of contrast enhanced MRI in differentiating benign and malignant pancreatic endocrine tumors (PNETs). Methods MRI findings on 13 cases who were pathologically diagnosed as PNETs were retrospectively analyzed, including the tumor volume, border, MRI signal and adjacent organ involvement of Grade 1~3 tumors, and the sensitivity, specificity and accuracy of MRI for diagnosing PNETs were calculated. Results A total of 18 tumors were detected, including 12 benign (Grade 1) and 6 malignant (Grade 2~3) tumors. Eight Grade 1 tumors′(66.7%) maximal diameters were ≤2 cm, while 100%(6/6) Grade 2~3 tumors′ maximal diameters were ≥2 cm. All of Grade 1 tumors (100%) had clear boundary, while 50%(2/4) Grade 2 and 100%(2/2) Grade 3 tumors had unclear boundary. Ten Grade 1 tumors (83.3%) had intratumoral homogeneous signal, while 100%(6/6) Grade 2~3 tumors had heterogeneous intratumoral signal. Two Grade 3 tumors (100%) had organ infiltration and retroperitoneal lymph node metastasis. The sensitivity, specificity and accuracy of MRI for differentiating benign and malignant PNETs were 83.3%, 85.7% and 84.6%, respectively. Conclusions MRI had higher sensitivity, specificity and accuracy in differentiating benign and malignant PNETs, but it was still difficult to differentiate Grade 1 from Grade 2 tumors by MRI. Tumors size could not be considered to be a reliable indicator for differentiating benign and malignant PNETs. Key words: Pancreas; Neuroendocrine tumor; Magnetic resonance imaging; Diagnosis, differential