Cystic Neoplasms of the Pancreas

Cystic neoplasms of the pancreas are uncommon but confusing diagnostic problems that are being encountered with greater frequency. They account for fewer than 10% of all pancreatic malignancies, but up to 30% of pancreatic resections performed, and they encompass a spectrum of benign, premalignant (borderline) and malignant lesions. Although they are less common, it is important to distinguish cystic neoplasms from the far more prevalent entity of benign pseudocysts, which are usually associated with a clinical history and radiographic evidence of pancreatitis. Cystic neoplasms of the pancreas can be classified into four major categories.

Categories

Serous Cystadenoma, the most common classification, is a
distinctly benign lesion characterized by a glycogen-rich epithelial lining. However, due to large size, they are often symptomatic causing pain, fullness, or early satiety. Some even cause biliary obstruction with jaundice, and/or segmental pancreatitis. They are radiographically recognized by a microcystic “ground-glass” or “cluster-of-grapes” appearance. Alternatively, they may demonstrate a classic “central scar”. These, if asymptomatic, can be safely observed since its malignant counterpart :

Serous Cystadenocarcinoma is an exceedingly rare occurrence. Symptomatic lesions are best treated with surgical resection.

Mucinous Cystadenoma/Adenocarcinoma harbor malignancy 50% of the time following resection (30% invasive, 20% carcinoma in-situ). They typically affect middle-aged women and are usually seated within the body or tail of the gland. They are characterized pathologically by mucin secretion from an ovarian-type stromal epithelial lining that generally is not in communication with the ductal system. Radiographically, they appear as single or multiple septated macrocystic spaces. The presence of papillary growths or wall calcification portends overt malignancy. Once diagnosed, surgical resection is recommended given the high frequency of malignancy, and is usually curative.

Solid Pseudopapillary Tumor (Franz Tumor, Hamoudi Tumor) is a rare, but distinct, entity that is characterized by masses with both solid and cystic components. It is usually found in young (Avg. age = 40) females and children, often in the body/tail of the pancreas. These large tumors are local-regionally invasive, but rarely metastatic, and demonstrate a more indolent course than pancreatic adenocarcinoma for which it may be confused. When limited to the pancreas, surgical resection is highly curative.

Intraductal Papillary Mucinous Neoplasm (IPMN/IPMT) is a newly recognized but poorly characterized neoplastic process involving the pancreatic duct epithelium in a fashion analogous to the “adenoma-to-carcinoma” sequence of colorectal cancer. Although morphologically variable, tumors can be classified into main-branch and side-branch variants with the latter, thought by some, as having a better prognosis. The hallmark is pancreatic ductal dysplasia to various degrees, although carcinoma in situ and overt invasive adenocarcinoma are present in around 50% of these tumors - more frequently in main-branch disease. It is classically, but infrequently, identified as a “fish-mouthed”, mucin-secreting Ampulla of Vater on endoscopy in a patient with identified cystic ductal changes on imaging. Some IPMNs can be safely watched/monitored (Side-branch, < 2cm) but most require resection of the diseased portion of the pancreas. The presence of biliary obstruction usually portends malignancy.

Symptoms

Cystic neoplasms present in a variety of ways. Many, indeed, are asymptomatic and are first discovered incidentally during radiographic (CT, MRI, US) investigations of the chest, abdomen and pelvis for other conditions. This form of recognition appears to be increasing in frequency. Unexplained abdominal or back pain is the most common complaint. This is often vague, nagging and progressive in scope. Nonspecific fullness, bloating and early satiety are frequent complaints. Some lesions present in a similar fashion to pancreatic adenocarcinoma with obstructive jaundice due to impingement of the bile duct. This finding is highly suggestive of underlying malignancy within the cyst. Similarly, pancreatitis (both acute and recurrent) can be the heralding sign. Often this may manifest as LUQ and/or back pain as a result of segmental pancreatitis from distal pancreatic duct obstruction.

Diagnosis

Management options hinge upon accurate diagnosis. Usually mucinous versus non-mucinous lesions can be determined preoperatively based on high quality imaging, endoscopy, and/or endoscopic ultrasound (EUS) guided FNA biopsy.

Obviously it is imperative to rule out a pancreatic pseudocyst, and this largely can be correlated with a history, physical and imaging exam indicative of pancreatitis.

“Screening” radiographic techniques such as single phase CT or transabdominal US initially define that a cystic process is present in the pancreas. However, they are not powerful or specific enough to properly define the true nature of the cyst.

Either triple-phase helical CT or MRI is ideal for delineating finer detail including internal septations, papillary growths, heterogeneity, mural calcification, and connections with the main pancreatic duct or its side branches. Often these are complementary modalities.

The use of PET scanning for defining malignancy in these cysts shows promise, but is not widely accepted currently.

Cyst fluid evaluation is an important diagnostic adjunct and is easily performed via aspiration under EUS guidance. Contents can be sampled for cellularity, mucin, amylase, viscosity and tumor markers such as CEA and CA 19.9. An aspirate CEA level over 200 is highly suggestive of a mucinous lesion, but not necessarily malignancy.

Treatment

Surgical consultation is advised as most cystic neoplasms will require operative intervention for either definitive diagnosis or treatment. The decision to perform a pancreatic resection should be based on the suspicion of malignancy compared with the relative risk to the individual patient.

In some cases, such as asymptomatic patients with either serous cystadenoma or side-branch variant IPMN (< 2 cm), no intervention is required. However, serial clinical and radiographic followup is recommended. Asymptomatic equivocal lesions for which no intervention is planned must also be followed with vigilance. Changes in character, growth of the lesion, or development of symptoms during watchful observation indicate reasons for operative intervention.

In cases of mucinous lesions and most IPMNs, surgical resection is advised given their premalignant nature. In fact, many of these (up to 50%) will harbor carcinoma in situ or overt invasive malignancy at time of diagnosis.
Solid pseudopapillary tumor is a true malignancy that warrants surgical resection when diagnosed.

If resection is indicated, a variety of procedures are employed, dictated largely by anatomic position of the lesion within the gland. Head and Uncinate process-based tumors require Pancreaticoduodenectomy (Whipple’s resection). Body and tail lesions require distal pancreatectomy, with or without splenectomy. In selected cases, and only by highly trained specialists, this may be achieved in a minimally-invasive laparoscopic fashion. For some premalignant lesions in the body, a central pancreatic resection may be feasible or simple enucleation of the cyst may be possible. Total pancreatectomy may be necessary in those rare occasions when IPMN involves the whole gland.

Risks and Outcomes

Pancreatic resections remain significant interventions for any patient. Hospital stays range from ten to fourteen days in most instances. Morbidity rates range from 30 to 40%.

The most significant postoperative complication is pancreatic fistula, occurring around 25% of the time in skilled hands (for both head and tail resections). The primary risk factors for development of a fistula are glandular characteristics such as a soft texture and/or a small pancreatic duct diameter. Today, this problem is usually managed conservatively and rarely requires reoperation.

Operative risks may also arise from co-morbid conditions such as cardiac, pulmonary, or renal disease. The mortality rate in a good-risk patient undergoing elective operation is 2-5% for pancreaticduodenectomy and under 1% for distal pancreatectomy.

Other considerations include the potential development of postoperative diabetes and exocrine insufficiency. This is often the case following total pancreatectomy, where patients may develop brittle diabetes. Oral enzyme replacement pills are available to assist with digestive malabsorption.

If splenectomy is performed consensus has not generally been reached for post-splenectomy immunization in adults. In children polyvalent vaccination is given to immunize against the future development of infection by Streptococcus Pneumoniae, H influenzae, or Meningococci species. Adults should receive, at the very least, the pneumococcal vaccine. Some authors recommend that the adult receive all three vaccinations as well; however, there is no evidence that the addition of the other two vaccinations provide any additional benefit. Vaccination should be given either two weeks before or after splenectomy with the most recent evidence showing that two weeks after splenectomy is ideal.

Surgical resection is a definitive and complete procedure in most cases and long-term follow-up is rarely required. The exception is with IPMN where radiographic surveillance of the remnant pancreas is justified. Currently annual CT or MRI evaluation after resection is practiced, however precise guidelines for this sort of surveillance are not clearly defined in that the natural history of this process is still poorly defined. In those cases of IPMN, mucinous, or solid pseudopapillary tumors that harbor invasive malignancy, appropriate adjuvant chemo and/or radiation therapy may be justified. In these cases, oncologic outcomes (i.e. long-term survival) mirror those for any other invasive pancreatic adenocarcinoma.

Qualifications for performing surgery on the pancreas
The qualifications of a surgeon performing any operative procedure should be based on training (education), experience, and outcomes. At a minimum, surgeons who are certified or eligible for certification by the American Board of Surgery, the Royal College of Physicians and Surgeons of Canada, or their equivalent should perform pancreatic resections. In addition to the standard residency training, qualifications should be based on advanced training, experience, and outcomes. More favorable outcomes have been demonstrated in the hands of surgical specialists who practice in centers where a high volume of these procedures are performed each year.

Suggested Readings
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