Mucinous cystic neoplasms of the pancreas: definition of preoperative imaging criteria for high-risk lesions

Background/aim: Pancreatic mucinous cystic neoplasms (MCN) are premalignant lesions whose natural history is poorly known. Whether the dysplasia grade might be determined with precision by preoperative clinical and imaging criteria is not known. We aimed to determine if CT scan data might be useful to predict the grade of dysplasia in a series of 60 histologically proven MCN.

Methods: All consecutive patients who were operated on with pathological confirmation of MCN were included. Careful CT scan evaluation was reviewed without knowledge of pathological results. Imaging and pathological results were correlated.

Results: Sixty patients (59 females) were included. Low- and intermediate-grade dysplasias were identified in 47 and 3 patients (benign MCN), respectively, and high-grade dysplasia and invasive carcinoma in 7 and 3 patients (malignant MCN), respectively. Patients with benign lesions were significantly younger. None of the studied clinical data were statistically different to distinguish benign and malignant MCN, except age (42 vs. 48 years, p < 0.05). Only maximal diameter and mural nodules on CT scan were significantly more frequent in the malignant group. No malignant MCN had a maximal diameter <40 mm. At a 40-mm threshold, the sensitivity and specificity of the maximal diameter to diagnose malignant MCN were 100 and 54%, respectively. Mural nodules seen on CT scan were confirmed in all cases but one upon pathological examination of the surgical specimen. The sensitivity and specificity of the presence of a mural nodule seen on CT scan for the diagnosis of a malignant lesion were 100 and 98%, respectively.

Conclusion: Preoperative CT scan detection of a mural nodule within a cystic pancreatic neoplasm suggestive of MCN strongly suggests malignancy. A diameter <40 mm is associated with no risk of malignancy.