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Introduction: Given the increased use of cross-sectional radiologic imaging in recent years, cystic lesions of the pancreas are now being diagnosed with greater frequency. The majority of these lesions are premalignant cystic neoplasms of the pancreas, such as intraductal papillary mucinous neoplasms (IPMNs) and mucinous cystic neoplasms (MCNs). While pseudocysts account for most of the remainder, there are a number of rare, benign cystic lesions of the pancreas that can mimic neoplastic cysts. The objective of this study was to review a single institution’s experience with these benign cystic lesions of the pancreas.
Methods: We conducted a retrospective analysis of all patients who underwent surgical resection for pancreatic lesions from 2005-2011 at our institution. Out of a total of 947 pancreatic resections, we isolated those cases performed for benign cystic disease and then examined the clinicopathological data on these patients.
Results: Thirteen patients (1.5%) out of a total of 170 pancreatic operations performed for cystic disease were found to have non-neoplastic cystic lesions of the pancreas (9 distal pancreatectomies, 4 pylorus-preserving pancreaticoduodenectomies). Preoperative imaging revealed primary lesions in all patients, 6 of which were found incidentally. Preoperative clinical and imaging studies suggested that 11 lesions were consistent with mucinous neoplasms and 2 with pancreatic adenocarcinoma. However, postoperative pathology revealed 5 patients with ductal retention cysts, 4 squamoid cysts, 1 mucinous non-neoplastic cyst, 1 congenital ciliated foregut cyst, 1 endometrial cyst, and 1 lymphoepithelial cyst. Two patients had complications postoperatively, 1 pancreatic fistula and 1 superior mesenteric vein thrombosis, both of which resolved with conservative management. All patients remain disease free with median follow up of 2 years post resection.
Conclusions: While pseudocysts tend to reflect inflammation and necrosis of the pancreas, there exist rare non-neoplastic cystic lesions that may not be associated with any underlying disease process. In our institutional experience, these lesions are often indistinguishable from premalignant cystic neoplasms of the pancreas preoperatively despite advances in diagnostic imaging and endoscopic ultrasound fluid analysis. Although it is possible to safely perform pancreatic resection in these patients, it is unnecessary if the patient is asymptomatic. It is important to recognize the existence of these entities to aid in avoiding surgical resection when not clinically indicated.

Table 1:Clinicopathological Data of 13 Patients With Non-neoplastic Cystic Lesions of the Pancreas

Patient	Age	Sex	Pre-op Symptoms	Pre-op Imaging	EUS Results	Procedure	Pathology
1	78	F	Abdominal Pain	CT	Not Performed	PPPD	Squamoid Cyst
2	66	M	None	CT, MRI	Not Performed	DPS w/ partial Left Hepatectomy	Squamoid Cyst, Hepatocellular Carcinoma
3	80	F	None	CT, MRI	Not Performed	DPS w/ partial Right Hepatectomy	Ductal Retention Cyst, Cholangiocarcinoma
4	49	F	None	CT	Epithelial Cells	DP	Ductal Retention Cyst
5	56	F	Pancreatitis	CT	No cells obtained	DPS	Ductal Retention Cyst
6	37	M	Pancreatitis	CT	Epithelial Cells	PPPD	Squamoid Cyst
7	65	M	None	CT, MRI	Mucin	DPS	Congenital Ciliated Foregut Cyst
8	32	F	Abdominal Pain	CT	Amylase, Elevated CEA	DPS	Endometrial Cyst
9	72	F	None	CT	Not Performed	Laproscopic DP	Squamoid Cyst
10	77	F	Abdominal Pain	MRI	Atypical	PPPD	Ductal Retention Cyst
11	52	F	Nausea	CT	Mucin	PPPD	Mucinous Non-neoplastic Cyst
12	46	F	Pancreatitis	CT	Not Performed	DPS	Ductal Retention Cyst
13	69	M	None	CT, MRI	Not Performed	DPS	Lymphoepithelial cyst

PPPD, Pylorus- preserving Pancreaticoduodenectomy; DPS, Distal Pancreatectomy & Splenectomy; DP, Spleen-preserving Distal Pancreatectomy