Pancreatic mucinous cystic neoplasm defined by ovarian stroma: demographics, clinical features, and prevalence of cancer.

Background & Aims: Pancreatic mucin-producing cystic neoplasms are classified into 2 distinct entities: mucinous cystic neoplasm (MCN) and intraductal papillary mucinous neoplasm (IPMN). In previous studies, MCN often has been defined loosely and has not always been distinguished clearly from IPMN. Our aims were to determine the demographics, clinical features, and prevalence of invasive cancer in MCN defined by the presence of characteristic ovarian stroma.

Methods: By using the presence of ovarian stroma as a requisite criterion for diagnosis of MCN, a single pathologist, unaware of clinical information, identified 56 MCNs from 243 mucin-producing neoplasms resected at Mayo Clinic between 1986 and 2003. Medical records of the MCN patients were reviewed to obtain clinical and demographic data.

Results: Patients with MCN were almost exclusively (98%) women; we identified 1 man with a neoplasm containing ovarian stroma. The mean (+/-SD) age at resection was 48 +/- 15 years (84% < 60 y). Abdominal pain was the most common presenting symptom; 16% were asymptomatic. Most MCN (93%) were in the pancreatic body/tail region. Their median size was 5 cm (61% > or =5 cm). Histologically, 50 (89%) were adenomas, 2 (4%) had carcinoma-in-situ, and 4 (7%) had invasive cancer. None of the 22 MCNs <5 cm in size had invasive cancer. No patient with noninvasive disease had a recurrence after resection.

Conclusions: MCN defined by ovarian stroma has a distinct demographic and clinical profile and a low prevalence of invasive cancer. These observations suggest that ovarian stroma should be used as the defining criterion for diagnosing MCN.