Over the past four decades, the mortality of pancreatic resection has improved significantly at high-volume centers. As a result, the most common procedures performed for small neuroendocrine and cystic tumors of the pancreas are pancreatoduodenectomy and distal pancreatectomy. However, the short- and long-term morbidity of a major pancreatic resection remains high. Thus, debate continues as to whether small benign and premalignant lesions of the pancreas should be observed or resected. In comparison, enucleation is a low-risk procedure that preserves pancreatic parenchyma and function. Thus, pancreatic enucleation may be an underutilized procedure that should be considered for small, frequently asymptomatic, pancreatic lesions that, if observed, have the potential to grow and metastasize.

The most common pancreatic lesions that may be enucleated are small, functioning neuroendocrine tumors. The diagnosis of insulinoma, gastrinoma, vasoactive intestinal peptide producing tumor (VI Poma) and glucagonoma may be established with a careful history, physical examination (for the rash with glucagonoma) and appropriate laboratory studies. For nonfunctioning PNETs, a serum chromogranin A also may be elevated. For the remaining lesions where enucleation may be indicated, no serum markers are available (Table 9.1).

A pancreatic lesion that may result in enucleation is most often discovered on a computerized tomography (CT) of the abdomen (Fig. 9.2). This study may be performed for vague symptoms, usually pain, or for other reasons such as an evaluation for kidney stones. As concern increases for the over exposure to radiation with repeated CT scans, magnetic resonance imaging (MRI) also is detecting more small pancreatic lesions. Magnetic resonance cholangiopancreatography (MRCP) also may be more sensitive than CT at detecting small cystic pancreatic tumors. In addition to CT and MRI, percutaneous ultrasound (US) may detect small pancreatic lesions, but percutaneous US is not as sensitive as CT and MR.

Endoscopic ultrasound (EUS) with fine needle aspiration (FNA) for cytology, the presence of mucin, amylase, carcinoembryonic antigen (CEA) and chromogranin A (CGA) is being performed more frequently to decide whether to observe or to operate. However, the accuracy of CT, MRI or EUS, even with FNA, is at best 75% to 85% in establishing a correct diagnosis. All of these imaging modalities are able to accurately locate the lesion within the pancreas. However, MRCP may be the best at demonstrating the relationship between the lesion and the main pancreatic duct as well as the communicating duct in side-branch IPMNs (Fig. 9.1B).

The remainder of the preoperative preparation for pancreatic enucleation does not differ significantly from other pancreatic surgery. Evaluation of the patient’s general health, including cardiopulmonary, renal and hepatic function is indicated. However, the relative risk to life is significantly less for enucleation than for pancreatic resection. Data from the American College of Surgeons—National Surgical Quality Improvement Program suggest that the relative risk of mortality following enucleation is one-sixth that of distal pancreatectomy and one-tenth of pancreatoduodenectomy. Thus, the decision to operate in elderly patients with comorbidities may favor surgery if enucleation is the planned operation. Blood loss is less with enucleation than with resection, and the need for a blood transfusion is unlikely. Nevertheless, typing and cross matching blood is reasonable. Pancreatic enucleation is a “clean” operation so preoperative administration of a first generation cephalosporin is adequate antibiotic prophylaxis. As the operative time for enucleation is less than for resection antibiotic redosing intraoperatively usually is not necessary.

The first decision is whether to perform the operation minimally invasively or open. This choice will be based on surgeon expertise, patient preference and location of the lesion. For potentially malignant lesions, the first step is to examine the peritoneum and surface of the liver for metastases. If none are found, ultrasound of the liver also should be performed. Again, in the absence of metastatic disease, the next step is to widely expose the pancreas. In general, tumors and/or cysts that are anterior to the pancreas will be more amenable to enucleation. However, lesions that lie posteriorly in the head and/or uncinate can be enucleated but an extensive Kocher maneuver will be required. Once the lesion has been exposed, intraoperative ultrasound imaging is performed to further assess (a) involvement/relationship to the main pancreatic duct, (b) whether the lesion is cystic or solid, (c) if cystic, whether mural nodules are present, and (d) whether other pancreatic lesions are present. If concern exists that enucleation will result in injury to the main pancreatic duct or if a mural nodule is encountered, resection should be undertaken.

To proceed with enucleation of a deep lesion, the pancreatic parenchyma overlying the tumor or cyst should be carefully opened with small vessels being ligated with fine sutures or cauterized. However, most lesions that are amenable to enucleation are on or close to the surface of the pancreas. As a result, dissection is begun at the edges of the lesion and continues with care being taken to stay close to but not entering the tumor or cyst. For neuroendocrine tumors, staying in the correct plain between the pancreas and the tumor is usually straight forward (Fig. 9.3A). This goal may be somewhat more difficult for mucinous cystic neoplasms (Fig. 9.3B) and for side-branch IPMNs because the wall of the cyst may be quite thin.

When enucleating neuroendocrine tumors, mucinous cystic neoplasms, serous cystadenomas, solid pseudopapillary neoplasms and lymphangiomas, no direct connection exists between the lesion and the pancreatic ductal system. However, when enucleating side-branch intraductal papillary mucinous neoplasms, a goal is to identify and, when possible, ligate the communicating duct (Fig. 9.4). In general, frozen section is performed to (a) make a final diagnosis and (b) for cystic lesions, to be sure that no carcinoma in situ or invasive cancer is present. However, the likelihood of discovering cancer at this stage is extremely low as the presence of invasion will generally preclude enucleation. For neuroendocrine tumors, injection of 1 or 2 ml of methylene blue dye into the cavity to determine the location of sentinel node(s) may be appropriate.