Cystic Pancreatic Endocrine Neoplasms: A Distinct Tumor Type?

Background: Cystic pancreatic endocrine neoplasms (CPENs) are considered rare, and their behavior is thought to be similar to that of solid pancreatic endocrine neoplasms (PENs). This study aims to describe the characteristics of CPENs in a large patient cohort. Study Design: We performed a retrospective review of 170 patients who underwent resections for PENs at Massachusetts General Hospital from 1977 to 2006. Twenty-nine patients (51% men, mean age 53) with CPENs were compared with 141 patients with solid PENs. Differences in clinical presentation, pathologic and radiographic features, and survival were described. Results: CPENs comprised 17% of all PENs (29 of 170) and 5.4% of all resected cystic pancreatic neoplasms(29 of 535). Ten (34%) were purely cystic and 19 (66%) were partially cystic. Compared with solid PENs, CPENs were larger (49 mm versus 23.5 mm, p < 0.05), more likely symptomatic (73% versus 45%, p < 0.05), and more likely nonfunctional (80% versus 50%, p < 0.05). They expressed synaptophysin (100%), chromogranin (82%), and cytokeratin (CK)-19 (24%). Multiple endocrine neoplasia type 1 (MEN-1) was 3.5 times more common in CPENs than in solid tumors (21% versus 6%, p < 0.05). No significant difference was found in location, propensity for metastasis, invasion, or 5-year survival (87% versus 77%, p = 0.38). Conclusions: This series, the largest report of CPENs in the literature, shows that CPENs are more common than previously thought, so they should be included in the differential of the cystic lesions of the pancreas. CPENs are larger and more likely to be symptomatic then solid PENs. They are also more likely to be associated with MEN-1 and to be nonfunctional, suggesting they may be a distinct tumor type.