Experience-based surgical approach to pancreatic mucinous cystic neoplasms with ovarian-type stroma.

The present study aimed to elucidate the clinicopathological characteristics of resected mucinous cystic neoplasm (MCN) with ovarian-type stroma and identify a surgical approach for MCN treatment, on the basis of Republic of Korean (Yonsei University College of Medicine, Seoul, South Korea) and Japanese (Nippon Medical School, Tokyo, Japan) bi-institutional collaboration. The present study retrospectively reviewed 55 MCNs with ovarian-type stroma using pathological re-examination. Clinicopathological features and preoperative clinical parameters were evaluated to predict malignant alterations in MCNs. The proportion of surgically treated MCNs has recently been increasing. All patients included in the present study were female, with a mean age of 47.9±13.3 years. Mural nodules were noted in 8 patients (14.5%) and the mean cyst size was 6.1±4.2 cm. A total of 9 patients (16.4%) were identified to exhibit non-invasive mucinous cystadenocarcinoma. The number of patients with small tumors (R2=-0.079, P=0.038) and asymptomatic pancreatic MCNs (P=0.022) was significantly increased (P<0.05), which resulted in the more frequent application of minimally invasive surgery (P<0.001). During the follow-up period (mean, 51.6 months; range, 1.1-242.8 months), no recurrence or tumor-associated mortality was identified. The presence of mural nodules (P=0.002) and a tumor size ≥4.5 cm (P=0.027) were identified as potential clinical parameters for predicting malignant transformation. The significance of mural nodules in predicting malignant transformation was increased in large MCNs (≥4.5 cm) of the pancreas compared with small MCNs (<4.5 cm) (P=0.002). Overall, non-invasive pancreatic MCNs are not aggressive, and minimally invasive pancreatectomy may be an effective approach for suitable patients.