MR imaging of non-functioning endocrine tumors of the pancreas

The purpose of this study was to clarify the MR imaging characteristics of patients with non-functioning endocrine tumors of the pancreas. Fourteen patients with these tumors underwent MR imaging. The signal characteristics of the tumor on T1-, T2-, and contrast-enhanced T1-weighted images were evaluated. The enhancement pattern of the tumor on dynamic study was also examined. The degree of stromal fibrosis was evaluated on the pathologic specimen, and was then classified as mild, moderate, or marked fibrosis. On T1-weighted images, the tumors were hypointense in 12 of 14 cases. The signals of the tumors on T2-weighted images were varied. The tumors were hypointense in 1 case, isointense in 2 cases, hyperintense in 6 cases, and very hyperintense in the other 5 cases. On contrast-enhanced T1-weighted images, the tumors were hyperintense in 8 cases and very hyperintense in 5 cases. On T2- and contrast-enhanced T1-weighted images, 4 of 5 malignant tumors were very hyperintense. Dynamic study revealed prolonged enhancement in 10 of 11 cases. Pathologic analysis revealed moderate or marked fibrosis in 10 of 14 cases, and prolonged enhancement was considered to be related stromal fibrosis. In conclusion, MR imaging findings of non-functioning endocrine tumors of the pancreas vary in relation to pathological variety. Prolonged enhancement of the tumor on dynamic study is considered to be one of the characteristic MR imaging findings that corresponds to stromal fibrosis of the tumor. (author)