Chronic Pancreatitis, Pancreatic Cysts, and Pancreatic Neoplasms: Chronic Pancreatitis and Cysts: Naming the Cyst

0:00Welcome to Board Pearls. This is episode four of five of the Chronic Pancreatitis, Pancreatic Cysts, and Pancreatic Neoplasms chapter, in the Pancreatic and Biliary Disease module. This episode is the pancreatic cyst, from naming it to deciding whether it comes out. The first patient is a woman with a cyst found on a scan for kidney stones, and her case shows what to establish first about any cyst, the five types and who gets each, what carcinoembryonic antigen, glucose, and amylase in the fluid each show, how CEA and amylase combine to name the cyst, and what cytology, KRAS, GNAS, and the string sign add. A young woman with a part-solid mass shows the cyst that's cured by resection. The second patient is a man with a branch-duct intraductal papillary mucinous neoplasm, followed over years, and his case shows how often to image and with what, the worrisome features that send a patient to endoscopic ultrasound, the high-risk stigmata that send a patient to a surgeon, how fast growth has to be, and when surveillance can stop.

1:04Here's the first patient. A forty-eight-year-old woman had a computed tomography, CT, scan for kidney stones that showed a four-centimeter cyst in the tail of her pancreas with thin internal septations. She's never had pancreatitis and doesn't drink. Her main pancreatic duct is normal, and on magnetic resonance cholangiopancreatography, MRCP, the cyst doesn't connect with it. She feels well.

1:30She has an incidental pancreatic cyst, and the first thing to establish is whether it's mucinous, because mucin is what carries cancer risk. Pancreatic cysts appear on two to fourteen percent of cross-sectional abdominal scans, rising to more than a quarter of people over eighty, and most are asymptomatic and found incidentally. Mucinous epithelium, in intraductal papillary mucinous neoplasm, IPMN, and mucinous cystic neoplasm, MCN, harbors progressive dysplasia, with risk that scales with size and main-duct involvement. Serous cystadenomas, true cysts, and retention cysts have negligible malignant potential. So mucinous cysts get surveillance or resection, and non-mucinous ones usually get nothing.

2:16Her features are read against five types, distinguished on cross-sectional imaging plus endoscopic ultrasound, EUS, and the most common is the one defined by the duct. IPMN is the most common neoplastic cyst, typically in patients over sixty, in men and women equally, and duct communication is pathognomonic for it. Branch-duct IPMN looks like a cluster of grapes, with a main duct under five millimeters and the lowest malignancy rate. Main-duct IPMN has a main duct over five millimeters and a fishmouth ampulla at endoscopy from extruded mucin, with malignancy in thirty to seventy percent at resection. Mixed-type IPMN combines the two.

2:56The other mucinous cyst is defined by who gets it and where. MCN occurs in women in more than ninety-five percent of cases, aged forty to sixty, in the pancreatic body or tail. It's often septated and doesn't communicate with the main duct, it has ovarian-type stroma on pathology, and its malignancy rate is ten to seventeen percent. Once EUS-guided aspiration confirms it, resection is recommended in a fit patient, because that risk is substantial.

3:25The non-mucinous types look different and behave differently. Serous cystadenoma arises from centroacinar cells, seventy-five percent in women aged fifty to seventy, anywhere in the pancreas, with a microcystic honeycomb appearance, a pathognomonic central scar in about twenty percent, and malignancy under one percent. It needs no resection or surveillance unless it causes symptoms. Multiple serous cystadenomas occur in von Hippel-Lindau syndrome, because the VHL gene drives the centroacinar phenotype. A pseudocyst is recognized by a history of pancreatitis. Her age, sex, septated tail cyst, and lack of duct communication point to MCN, but imaging can't confirm mucin.

4:06Her fluid supplies what imaging can't, starting with mucin. A cyst fluid carcinoembryonic antigen, CEA, above one hundred ninety-two nanograms per milliliter favors a mucinous cyst, with a sensitivity of about seventy-three percent and a specificity of eighty-four, because mucinous epithelium secretes CEA. A CEA below five has eighty-five percent specificity for excluding one. Fluid glucose below fifty milligrams per deciliter is more sensitive, over ninety percent in pooled data, because mucinous epithelium consumes glucose, while non-mucinous fluid keeps the glucose that diffuses in from serum. Fluid amylase answers a different question, duct communication. Amylase above two hundred fifty units per liter supports communication with the duct, meaning IPMN or pseudocyst, and amylase below two hundred fifty has ninety-eight percent specificity for excluding a pseudocyst. Her EUS aspirate shows a CEA of five hundred forty, a glucose of twenty-two, and an amylase of sixty: mucinous, without duct communication.

5:10Her two answers combine into a simple two-by-two, with mucin from CEA and glucose on one side and duct communication from amylase on the other. High CEA with high amylase is IPMN. High CEA with low amylase is MCN. Low CEA with high amylase is a pseudocyst. Low CEA with low amylase is a serous cystadenoma. Hers is MCN, matching her imaging and her demographics; when fluid and imaging disagree, they're reconciled before anyone acts. An amylase of four thousand with the same CEA would have meant IPMN and a second look at the MRCP for a missed communication. A CEA of three with an amylase of forty would have meant a serous cystadenoma, needing nothing unless it caused symptoms.

5:57Because CEA alone can mislead, other fluid tests are used to confirm mucin. Cytology has a sensitivity of only about sixty-three percent but a high specificity, because shed mucinous cells are sparse in viscous fluid, so positive cytology matters and negative cytology rules nothing out. KRAS supports a mucinous cyst, with a sensitivity of forty-five to sixty-five percent and a specificity of ninety-six to one hundred percent. GNAS, found in forty to sixty-five percent of IPMNs, points to IPMN rather than MCN, because its activating pathway is specific to IPMN. The string sign, fluid that pulls to more than a centimeter or holds for more than a second, supports mucin with ninety-five percent specificity, because mucin is more viscous than serous fluid. Through-the-needle biopsy adds accuracy at expert centers, as chapter twenty-nine covers. Her string sign is positive, KRAS is detected, and GNAS isn't, which confirms MCN, so she's referred for resection.

7:01The fifth type is recognized by age and by its solid component. A twenty-six-year-old woman with vague upper abdominal discomfort has a five-centimeter, well-circumscribed, part-solid, part-cystic mass in her pancreatic head. Her EUS cytology shows branching, finger-like papillary projections with nuclear beta-catenin staining, reflecting CTNNB1 mutations. She has a solid pseudopapillary epithelial neoplasm, which is rare, more than eighty percent in women aged twenty to forty, with a malignancy rate of eight to twenty percent but an indolent course. Resection is curative, and she's referred for it. Cystic neuroendocrine tumors and cystic degeneration of adenocarcinoma can also present as cysts, as episode five covers.

7:47The second patient has the most common neoplastic cyst, and his question is surveillance rather than resection. A sixty-four-year-old man had a CT for diverticulitis that showed a sixteen-millimeter cyst in his pancreatic head, communicating with a side branch on MRCP, with a three-millimeter main duct, no nodule, and a thin wall. He has no jaundice, diabetes, or pancreatitis, and he's fit and active.

8:11A cyst communicating with a side branch with a normal main duct is a branch-duct IPMN, and without worrisome features, it's watched. Magnetic resonance imaging, MRI, with MRCP is preferred over CT, because it shows the duct communication that defines IPMN without radiation over a lifetime of imaging, with CT or EUS reserved for patients who can't have MRI. The interval is set by size. A cyst under one centimeter is imaged every six months for a year and then every one to two years. One to two centimeters is imaged yearly for two years and then every two years. Two to three centimeters is imaged every six to twelve months. Over three centimeters is already a worrisome feature and gets EUS plus MRI every three to six months, with consideration of surgical referral. Guideline bodies set the schedule slightly differently, and the Kyoto twenty twenty-four guideline is the current international reference. His sixteen-millimeter cyst gets yearly MRI for two years.

9:13What he's watched for are the worrisome features, defined by the Fukuoka twenty seventeen consensus and the Kyoto twenty twenty-four guidelines. They are a cyst of three centimeters or more, an enhancing mural nodule under five millimeters, thickened enhancing walls, a main duct of five to nine point nine millimeters, an abrupt change in main duct caliber with downstream atrophy, suggesting main-duct involvement, lymphadenopathy, a raised carbohydrate antigen 19-9, growth of two point five millimeters or more a year, new or recent diabetes, and acute pancreatitis. Kyoto revised the older growth threshold of five millimeters over two years to a rate of two point five millimeters a year.

9:53His cyst grows, and its rate of growth is what crosses the line. It reaches seventeen and then twenty millimeters, about two millimeters a year, below the threshold, but at twenty millimeters his interval shortens to six to twelve months. Nine months later it's twenty-four millimeters, faster than two point five millimeters a year, which is a worrisome feature. His tumor marker, nodes, glucose, wall, and duct caliber are otherwise unremarkable.

10:18His worrisome feature triggers EUS with fine-needle aspiration, not surgery, because worrisome features mark intermediate risk, where more data refine the decision. EUS gives higher resolution of nodules, separates a true enhancing nodule from a mucin globule that can look similar on MRI, detects subtle main-duct involvement, and provides fluid for biochemistry and molecular testing. His EUS shows a three-millimeter enhancing mural nodule, a three-millimeter main duct, and cytology without atypia, so he has two worrisome features, rapid growth and a small nodule. He's fit, and he's referred to a pancreatic surgeon to weigh resection against closer surveillance.

11:00Surgery is mandatory only with a high-risk stigma, because those correlate with a substantial probability of high-grade dysplasia or invasive cancer. The four high-risk stigmata are obstructive jaundice with a cystic lesion in the head, which implies invasive growth into the bile duct; an enhancing mural nodule of five millimeters or more, or a solid component; a main duct of ten millimeters or more; and suspicious or positive cytology. With a high-risk stigma, referral to surgery is immediate in a fit patient, without a confirmatory EUS aspiration, because the indication is already established. A seven-millimeter enhancing nodule on his MRI, or jaundice with a bilirubin of five from his head cyst, would each have sent him straight to surgery. A cyst in the tail couldn't produce the jaundice stigma.

11:47His surveillance also has an end point, set by whether he'd ever have surgery. Surveillance continues indefinitely in fit patients, because the malignancy risk doesn't plateau over ten years of follow-up. It stops when the patient would no longer have surgery, or when life expectancy is under ten years, the American Gastroenterological Association threshold, which Kyoto also accepts, because imaging that can't lead to an operation only generates anxiety and incidental findings. An eighty-five-year-old woman with severe heart failure and oxygen-dependent lung disease, an eleven-millimeter branch-duct IPMN without worrisome features, and a cardiologist who says she wouldn't survive resection isn't surveyed at all.

12:28Some patients continue regardless of the cyst, because the rest of the gland is at risk. Younger patients, those with familial or genetic risk, and those whose surveillance is also screening for a ductal adenocarcinoma arising elsewhere in the pancreas continue, because that field-effect risk persists even when the cyst itself is stable. If he had two first-degree relatives with pancreatic cancer, he'd continue regardless of his cyst's stability. Hereditary surveillance is covered in chapter thirty-six.

12:56Here are the traps the boards set in cyst diagnosis. Every cyst is classified as mucinous or not before anything else is decided. Duct communication is the defining feature of IPMN. A confirmed MCN in a fit patient is resected, not surveyed. An asymptomatic serous cystadenoma is neither resected nor surveyed. Glucose is more sensitive than CEA for a mucinous cyst. A cyst with an amylase below two hundred fifty is almost never a pseudocyst. Negative cytology doesn't exclude anything. GNAS points to IPMN. And a young woman with a solid and cystic mass may have a solid pseudopapillary neoplasm.

13:35For IPMN, the traps are these. Years of surveillance are done with MRI, not CT. The interval shortens as a cyst grows. Growth is judged by the current rate of two point five millimeters a year. A worrisome feature goes to EUS first, while a high-risk stigma goes straight to surgery. A mucin globule isn't a nodule. A patient who would never have surgery isn't surveyed. And surveillance continues in younger patients and those with familial risk.

14:05So, start to finish. First ask whether a cyst is mucinous. IPMN connects with the duct, MCN is a middle-aged woman's body or tail cyst with ovarian stroma, resected when she's fit, serous cystadenoma is honeycomb with a central scar and needs nothing unless symptomatic, a solid pseudopapillary neoplasm is a young woman's solid and cystic mass cured by resection, and a pseudocyst follows pancreatitis. A CEA over one hundred ninety-two or a glucose under fifty means mucin, an amylase over two hundred fifty means duct communication, and together they name the cyst. KRAS and the string sign support mucin, GNAS points to IPMN, and cytology is specific but insensitive.

14:49Survey branch-duct IPMN with MRI at intervals set by size. Worrisome features go to EUS with aspiration, and high-risk stigmata go straight to surgery in fit patients. Stop when the patient could no longer have surgery, and continue in younger patients and those with familial risk.

15:07Episode five is pancreatic adenocarcinoma and pancreatic neuroendocrine tumors.

15:14For the full chapter, the practice vignettes, and the topic-tagged question bank, head to board pearls dot com. You'll find the rest of the series on Apple Podcasts, Spotify, or wherever you listen to podcasts. That brings us to the end of episode four of five of chapter twenty-six, and I'll see you in the next one.