MRI is useful to suggest and exclude malignancy in mucinous cystic neoplasms of the pancreas.

OBJECTIVES: To evaluate the value of MRI in differentiating benign (b-MCN) and malignant (m-MCN) MCN. European guidelines suggest that certain mucinous cystic neoplasms (MCN) of the pancreas can be conservatively managed.

METHODS: A retrospective single-center study of consecutive patients with resected MCN. MRIs were independently reviewed by two readers blinded to the pathological results. The authors compared b-MCN (i.e., mucinous-cystadenoma comprising high-grade dysplasia (HGD)) and m-MCN (i.e., cystadenocarcinoma).

RESULTS: Sixty-three patients (62 women [98%]) with 63 MCN (6 m-MCN, 2 HGD) were included. m-MCN tumors had a tendency to be larger than b-MCN (median 86 [25-103] vs. 45 [17-130] mm, p = .055). The combination of signal heterogeneity on T2-weighted imaging, wall thickness ≥ 5 mm, the presence of mural nodules ≥ 9 mm, and enhancing septa had an area under the ROC curve of 0.97 (95% CI 0.91-1.00) for the diagnosis of m-MCN. A total of 24 (37%), 20 (32%), 10 (16%), 5 (8%), and 4 (6%) out of 63 MCNs showed 0, 1, 2, 3, and 4 of these features, respectively. The corresponding rate of m-MCN was 0%, 0%, 10%, 20%, and 100%, respectively, with a good-to-excellent inter-reader agreement. Patterns with a high NPV for m-MCN included an absence of enhancing septa or walls (NPV 97% and 100%, respectively), wall thickness < 3 mm (NPV 100%), and no mural nodules (NPV 100%).

CONCLUSIONS: A combination of 4 imaging features suggests malignant MCN on MRI. On the other hand, visualization of a thin non-enhancing wall with no mural nodules suggests benign MCN.

KEY POINTS: • A heterogenous signal on T2-weighted MRI, a ≥ 5-mm-thick wall, mural nodules ≥ 9 mm, and/or enhancing septa suggest malignant MCNs. • A thin non-enhancing wall with no mural nodules suggests benign MCNs. • MRI should be performed in the pre-therapeutic evaluation of MCN to help determine the therapeutic strategy in these patients.