Mucinous cystic neoplasm of the pancreas: is surgical resection recommended for all surgically fit patients?

BACKGROUND: Surgical removal of mucinous cystic neoplasms (MCNs) is usually recommended because of the risk of malignancy. However, increased experience of MCNs suggests that the incidence of invasion is lower than had been thought. This study was designed to establish more reasonable surgical indications for MCN through re-assessment using strict pathologic diagnostic criteria.

METHODS: Ninety-four patients who underwent surgical removal of MCNs at Seoul National University Hospital from 1991 to 2012 were retrospectively analyzed. Pathologic results were re-evaluated by an experienced pathologist. Medical records and radiologic images were reviewed to determine factors predicting malignancy.

RESULTS: Of the 94 patients, 4 were found to have intraductal papillary mucinous neoplasms (IPMNs). Of the 90 MCNs, 60 (66.7%) were low-grade, 21 (23.3%) were intermediate-grade, and 5 (5.5%) were high-grade dysplasias; and 4 (4.4%) were invasive carcinoma. Mural nodules on CT scan (p = 0.005) and abnormal serum CA19-9 concentration (p = 0.029) were significant predictors of malignancy. All MCNs less than 3 cm in size with normal serum tumor markers were benign and all malignant MCNs had cyst fluid CA19-9 over 10,000 units/ml. The five year disease specific survival rates were 98.8% for all patients and 75.0% for those with invasive MCNs.

CONCLUSION: MCNs had a low prevalence of malignancy. Regardless of the histological grade, long-term outcome was excellent. Therefore, in the absence of specific symptoms, surgery may not be indicated for MCNs <3 cm without mural nodules or elevated serum tumor markers. Validation by a prospective study with very careful design is needed.