Smallest cystic tumor, measuring 5 mm, was identified as an invasive adenocarcinoma among multiple intraductal papillary-mucinous tumors

We encountered a case of four cysts of intraductal papillary-mucinous tumor in the pancreas, a 25-mm diameter tumor, a 20-mm tumor, and a 10-mm tumor in the pancreatic body and tail, and a 5-mm diameter tumor in the uncinatus process, and the smallest diameter intraductal papillary-mucinous tumor (5 mm) was regarded as an invasive papillary adenocarcinoma, while the other three intraductal papillary-mucinous tumors were adenomas. A 63-year-old asymptomatic male was indicated of the presence of multiple pancreatic tumors by computed tomography during a physical examination. Endoscopic retrograde cholangiopancreatography revealed three cysts (25 mm, 20 mm, 10 mm diameter tumor) in the pancreatic body and tail, and one cyst 5 mm) in the uncinatus process. Cytologic examination of the pancreatic juice determined them as Class V. Based on a diagnosis of malignant intraductal papillary-mucinous tumors, he underwent distal pancreatectomy with removal of the uncinatus process. Pathologically, three cysts in the body and tail of the pancreas were found to be adenomas, but the 5-mm cyst in the uncinatus process was found to be an invasive intraductal papillary-mucinous tumor. The interstitium had been invaded by cancer, and the uncinatus process was the cancer positive surgical margin, and cystological examination of the pancreatic juice through repeated endoscopic retrograde cholangiopancreatography resulted in a class V, so the patient underwent a total pancreatectomy. When diagnosing intraductal papillary-mucinous tumor(s), there is the possibility of incorrectly differentiating between benignancy and malignancy when the diagnosis is based on cyst diameter, as is conventional.     

Immunohistochemical study of genetic alterations in intraductal and invasive ductal tumors of the pancreas.

BACKGROUND/AIMS: Multiple genetic alterations are involved in the development of pancreatic neoplasm. Here we investigated the incidence of p53, ras, bcl-2 and c-erbB-2 gene alterations in intraductal papillary-mucinous tumors and invasive ductal adenocarcinoma of the pancreas by immunohistochemical method to identify and analyze their relationship in terms of these genetic alterations. METHODOLOGY: Fifty-four pancreatic lesions, including 18 benign (hyperplasia (3) and intraductal papillary adenoma (15)), and 16 malignant (carcinoma in situ (2) and intraductal papillary adenocarcinoma (14)) cases of intraductal papillary-mucinous tumor; and 20 cases of invasive ductal adenocarcinoma, were immunostained by avidin-biotin peroxidase conjugate method. RESULTS: p53 and rasp21 expressions were significantly greater in malignant intraductal (P < 0.01, P < 0.05) and invasive ductal (P < 0.01, P < 0.01) tumors than in benign intraductal papillary-mucinous tumors; while bcl-2 and c-erbB-2 expressions were significantly greater in invasive ductal adenocarcinoma than both benign (P < 0.01, P < 0.05) and malignant (P < 0.05, P < 0.05) intraductal papillary-mucinous tumors. CONCLUSIONS: Different groups of genetic alterations are involved in different phases of pancreatic tumorigenesis. p53 and ras gene alterations occur at an early stage during the development of intraductal papillary-mucinous tumor, while additional alterations of bcl-2 and c-erbB-2 occur during the development of invasive ductal adenocarcinoma of the pancreas.     

The role of pancreatoscopy in the preoperative evaluation of intraductal papillary mucinous tumor of the pancreas

BACKGROUND: Intraductal papillary mucinous tumor of the pancreas is a rare neoplasm managed by operative resection of the affected segment of the pancreas. GOALS: To evaluate the role of peroral pancreatoscopy in the diagnosis and preoperative localization of the affected region of the pancreatic duct and to undertake the appropriate operation for each patient. STUDY: Five patients with suspected intraductal papillary mucinous tumor of the pancreas were studied using endoscopic retrograde cholangiopancreatography, computed tomography of the abdomen, endoscopic ultrasonography, and peroral pancreatoscopy. The findings from these studies were compared, and operative resection was performed in each patient based on pancreatoscopic findings. RESULTS: Of the five patients with suspected intraductal papillary mucinous tumor, only four had histologically confirmed tumor, and the remaining one patient had a retention cyst of the pancreas. Pancreatoscopy correctly identified all four patients with the tumor while excluding the diagnosis of papillary tumor in one. CONCLUSION: Peroral pancreatoscopy is valuable in the preoperative evaluation of intraductal papillary mucinous tumor of the pancreas, especially in the localization of such tumor.     

Pancreatoscopy: An update

Per-oral pancreatoscopy(POPS) is an endoscopic procedure to visualize the main pancreatic duct. POPS specifically has the advantage of direct visualization of the pancreatic duct, allowing tissue acquisition and directed therapies such as stones lithotripsy. The aim of this review is to analyze and summarize the literature around pancreatoscopy. Pancreatoscopy consists of the classic technique of the mother-baby method in which a mini-endoscope is passed through the accessory channel of the therapeutic duodenoscope. Pancreatoscopy has two primary indications for diagnostic purpose. First, it is used for visualization and histological diagnosis of intraductal papillary mucinous neoplasms. In these cases, POPS is very useful to assess the extent of malignancy and for the study of the intraductal papillary mucinous neoplasm in order to guide the surgery resection margins. Second, it is used to determine pancreatic duct strictures,particularly important in cases of chronic pancreatitis, which is associated with both benign and malignant strictures. Therefore POPS allows differentiation between benign and malignant disease and allows mapping the extent of the tumor prior to surgical resection. Also tissue sampling is possible, but it can be technically difficult because of the limited maneuverability of the biopsy forceps in the pancreatic ducts. Pancreatoscopy can also be used for therapeutic purposes, such as pancreatoscopy-guided lithotripsy in chronic painful pancreatitis with pancreatic duct stones. The available data for the moment suggests that, in selected patients, pancreatoscopy has an important and promising role to play in the diagnosis of indeterminate pancreatic duct strictures and the mapping of main pancreatic duct intraductal papillary mucinous neoplasms. However, further studies are necessary to elucidate and validate the pancreatoscopy role in the therapeutic algorithm of chronic pancreatitis.     

PERORAL PANCREATOSCOPY: CURRENT STATUS AND FUTURE EXPECTATIONS USING NARROW BAND IMAGING

Peroral pancreatoscopy (POPS) under duodenoscopic assistance provide direct visual assessment of the pancreatic duct, tissue sampling, and therapeutic interventions. Sometimes, pancreatoscopy can confirm accurate diagnosis, such as differential diagnosis of filling defects between intraductal tumors and stones. However, it is often difficult to differentiate malignant from benign strictures solely on pancreatoscopy. It is currently considered that intraductal papillary mucinous neoplasm (IPMN) is the most suitable indication of POPS. POPS has several problems: image resolution, fragility and maneuverability. Concerning image resolution, the quality has been improved with the development of a video pancreatoscope. Moreover, the recently developed endoscopic optical technology of narrow band imaging (NBI) is now available to video pancreatoscopy. This will allow direct visual assessment. Although currently POPS has several problems, further improvement will assist POPS to become a useful modality in combination with NBI.     

Electronic pancreatoscopy for the diagnosis of pancreatic diseases

OBJECTIVES: Diagnostic pancreatoscopy was performed in 56 patients using the newly developed peroral electronic pancreatoscope (PEPS). The diagnostic value of the PEPS for pancreatic diseases was evaluated. METHODS: The PEPS (external diameter = 2.1 mm, bidirectional tip deflection) was developed with a minute 50,000-pixel interline charge-coupled device. Pancreatoscopy was performed by means of an endoscopic retrograde approach without sphincterotomy. The cases examined were normal (three), chronic pancreatitis (32), pancreatic cancer (eight), and intraductal papillary mucinous tumors (13). RESULTS: Of the 56 cases, 42 (75%) were adequately seen. In normal cases, fine capillary vessels were clearly visualized on the smooth whitish-pink mucosa. Findings in chronic pancreatitis included protein plugs, calcified stones, rough whitish mucosa, scar formation, edema, erythema, and indistinct capillary appearance. All the stenoses of chronic pancreatitis could be differentiated from those of pancreatic cancer with the PEPS. In the pancreatic cancer cases, all patients had stenoses or duct cutoffs; most cases had friable mucosa with erythema and erosive changes, and a single patient had a compressed pancreatic duct wall covered with normal epithelium. In the cases of intraductal papillary mucinous tumors, papillary tumors were visualized with extreme clarity. In the case of adenocarcinoma, the PEPS revealed oval-shaped tumors with spotty redness or villous tumors with dilation of capillary vessels. Moderate acute pancreatitis was recognized after pancreatoscopy in one of the 56 cases (1.8%). CONCLUSIONS: Electronic pancreatoscopy with the PEPS is feasible in most patients and technically safe, and improves diagnostic yield over conventional pancreatoscopy.     

Immunohistochemical analysis of expression of molecular biologic factors in intraductal papillary-mucinous tumors of pancreas--diagnostic and biologic significance.

BACKGROUND/AIMS: In this study we investigated the expressions of molecular biologic factors, p53, rasp21, bcl-2, c-erbB-2, and Ki-67 by immunohistochemical method in intraductal papillary-mucinous tumor of the pancreas to identify their diagnostic values and to determine their relations to the degree of histopathologic abnormalities. METHODOLOGY: Thirty-eight different histologic lesions from 28 patients of intraductal papillary-mucinous tumor of the pancreas, comprising normal pancreatic duct (n = 6), intraductal papillary hyperplasia (n = 6), intraductal adenoma (n = 15), and intraductal carcinoma (n = 11) were immunostained by the avidin-biotin peroxidase conjugate method. RESULTS: p53 and Ki-67 expressions were significantly greater in malignant intraductal papillary-mucinous tumor than in their benign counterpart (p = < 0.0001), while rasp21 showed gradual increase in the frequency of expression from normal pancreatic duct (0%), to intraductal hyperplasia (16.7%), to intraductal adenoma (26.7%), and ultimately to intraductal carcinoma (63.6%). bcl-2 and c-erbB-2 were not expressed in any lesions. CONCLUSIONS: These results suggest that p53 and Ki-67 expressions have significant diagnostic values in differentiating benign intraductal papillary-mucinous tumors from malignant ones and thus can facilitate in the pre-operative planning of treatment in individual cases. Secondly, gradual stepwise increase in the frequency of rasp21 expression with increasing degree of cellular atypia supports the presence of adenoma-carcinoma sequence in the carcinogenesis of this tumor.     

Immunohistochemical analysis of cyclooxygenase-2 expression in pancreatic tumors.

BACKGROUND: A considerable amount of evidence collected from several experimental systems and clinical studies with nonsteroidal Anti-inflammatory drugs (NSAIDs) indicates that Cox-2 may play a major role in colorectal tumorigenesis, but little information about Cox-2 expression in pancreatic tumors is available. In this study, we investigated Cox-2 expression by means of both immunohistochemical analysis and immunoblot analysis in pancreatic tumors. METHODS: Fifty invasive ductal adenocarcinomas and 26 intraductal papillary-mucinous tumors (IPMTs) were used for immunohistochemical analysis, and five pancreatic cancer tissues and five pancreatic cancer cell lines for immunoblot analysis. RESULTS: Cox-2 was expressed in 72% of the invasive ductal adenocarcinomas, 31% of intraductal papillary-mucinous adenocarcinomas, and none of intraductal papillary-mucinous adenomas. The expression rate of Cox-2 in intraductal papillary-mucinous adenocarcinomas was significantly higher than that in intraductal papillary-mucinous adenomas, and that in invasive ductal adenocarcinomas was significantly higher than that in intraductal papillary-mucinous carcinomas. However, there was no significant correlation between Cox-2 expression and the prognosis and clinicopathological factors. Immunoblot analysis identified Cox-2 in all of pancreatic cancer tissues and 60% of cell lines. CONCLUSION: The biological role of cyclooxygenase-2 (Cox-2) in carcinoma cells should be investigated with reference to the cancer progression of the pancreas.     

Immunohistochemical analysis of cyclooxygenase-2 expression in pancreatic tumors

Summary Background A considerable amount of evidence collected from several experimental systems and clinical studies with nonsteroidal Anti-inflammatory drugs (NSAIDs) indicates that Cox-2 may play a major role in colorectal tumorigenesis, but little information about Cox-2 expression in pancreatic tumors is available. In this study, we investigated Cox-2 expression by means of both immunohistochemical analysis and immunoblot analysis in pancreatic tumors. Methods Fifty invasive ductal adenocarcinomas and 26 intraductal papillary-mucinous tumors (IPMTs) were used for immunohistochemical analysis, and five pancreatic cancer tissues and five pancreatic cancer cell lines for immunoblot analysis. Results Cox-2 was expressed in 72% of the invasive ductal adenocarcinomas, 31% of intraductal papillary-mucinous adenocarcinomas, and none of intraductal papillary-mucinous adenomas. The expression rate of Cox-2 in intraductal papillary-mucinous adenocarcinomas was significantly higher than that in intraductal papillary-mucinous adenomas, and that in invasive ductal adenocarcinomas was significantly higher than that in intraductal papillary-mucinous carcinomas. However, there was no significant correlation between Cox-2 expression and the prognosis and clinicopathological factors. Immunoblot analysis identified Cox-2 in all of pancreatic cancer tissues and 60% of cell lines. Conclusion The biological role of cyclooxygenase-2 (Cox-2) in carcinoma cells should be investigated with reference to the cancer progression of the pancreas.     

ENDOSCOPIC DIAGNOSIS OF INTRADUCTAL PAPILLARY‐MUCINOUS NEOPLASM OF THE PANCREAS BY MEANS OF PERORAL PANCREATOSCOPY USING A SMALL‐DIAMETER VIDEOSCOPE AND NARROW‐BAND IMAGING

Background: Intraductal papillary‐mucinous neoplasm (IPMN) is an intraductal tumor in which the mucin‐producing epithelium shows proliferated papillary and a wide variety of pathological changes ranging from hyperplasia to adenocarcinoma. Therefore, it is important to determine whether an IPMN is benign or malignant. In the present study of patients with IPMN, the protrusion was observed by a peroral pancreatoscopy (PPS) using a small‐diameter videoscope and narrow‐band imaging (NBI). We carried out the differential diagnosis of benign lesion to malignant lesion. Methods: Between April 2003 and May 2009, PPS using a small‐diameter videoscope by means of NBI was carried out on 21 hospitalized patients with IPMN (10 cases of adenocarcinoma, 11 cases of adenoma or hyperplasia; 14 males and seven females, with a mean age of 69.4 years). Results: Fifteen focal lesions of the 16 cases in the head of the pancreas (93.7%) and four focal lesions of the five cases in the pancreatic body (80%) were observable, whereas two lesions (adenocarcinoma in the pancreatic body, and adenoma in the uncus of pancreas) were not observable. Endoscopically, seven cases were classified as villous type and two cases as vegetative type, and nine cases were diagnosed as adenocarcinoma. Ten cases with sessile type or semipedunculated type were diagnosed as adenoma or hyperplasia. Vascular patterns and protrusions were detected more clearly in the NBI images than under white light observation. Conclusions: When combined with a videoscope and NBI, pancreatoscopy provided a clear image and was useful for evaluating whether the IPMN was benign or malignant.     

Biliopancreatic fistula associated with intraductal papillary-mucinous pancreatic cancer: institutional experience and review of the literature

Intraductal papillary-mucinous tumour is clinicopathologically characterized by papillary growth and mucin production within the pancreatic duct system. The category includes a wide range of dysplasia, ranging from adenoma to carcinoma, the latter designated as intraductal papillary-mucinous cancer. In general, the tumor renders a favorable prognosis after complete resection. However, intraductal papillary-mucinous tumor with overt invasion outside the gland has been reported to have a poor prognosis, as is the case with the usual type of duct cell cancer of the pancreas. We experienced two cases of intraductal papillary-mucinous cancer with obstructive jaundice due to impaction of thick mucus protruding from the pancreas via a "spontaneous" biliopancreatic fistula. Preoperative examinations of both patients showed a large intraductal papillary-mucinous tumor in the head of the pancreas with fistula formation between the intrapancreatic portion of the common bile duct and the main pancreatic duct. Histopathological investigation of the two resected specimens suggested that the fistula may not have developed from invasion by papillary or tubular adenocarcinoma, but from compression and destruction of the intercalating tissues by abundant mucinous secretion. The first patient died of peritoneal carcinomatosis with clinicopathologic features of pseudomyxoma peritonei 6 years after surgery. The second patient is alive and has been well for 2 years postoperatively. Review of the world literature showed that half of the patients with intraductal papillary-mucinous cancer plus biliopancreatic fistula had no stromal invasion around the fistula, indicating that the fistula might have been caused by mechanical pressure. However, the other half of the cases did have stromal invasion around the fistula. Two-thirds of these cases, including our own patients, had foci of mucinous carcinoma in the stroma around the fistulization, implying that mucinous lakes in the stroma may have served as part of the "waterway" from the pancreatic duct to the bile duct, assisted by increased pressure by mucus production. Since intraductal papillary-mucinous cancer with biliopancreatic fistula has a comparatively favorable prognosis, surgical resection should be considered.     

ENDOSCOPIC DIAGNOSIS OF INTRADUCTAL PAPILLARY MUCINOUS NEOPLASM USING PERORAL PANCREATOSCOPY WITH NARROW BAND IMAGING

A 77‐year‐old man was diagnosed with a pancreas cyst at another hospital. Abdominal ultrasonography revealed a cyst in the head of the pancreas and a small protrusion. These findings suggested intraductal papillary mucinous neoplasm. Cytologic finding of the pancreatic juice revealed a Class III lesion, and intraductal ultrasonography and peroral pancreatoscopy (PPS) were performed. An abnormal course of main pancreatic duct (MPD) prevented the insertion of an ultrasonography probe into the MPD, and PPS was performed. The mucosal surface of the MPD near the papillary area was normal, and narrow band imaging (NBI) clearly showed the vascular structure. When the PPS was inserted more deeply, many small protrusions were observed and NBI delineated the protrusions more clearly. Papillary protrusions were observed in the cyst, but NBI did not reveal any tumor vessels. These findings led to a diagnosis of benign intraductal papillary mucinous neoplasm lesion. Since then, follow‐up examinations have been made. Changes in the cyst and protrusion have not been observed.     

Two cases of pancreatic ductal adenocarcinoma, manifested as solid pseudopapillary tumor and intraductal papillary mucinous neoplasm]

Compared with other types of cancers, pancreatic cancer is one of the most dreadful malignancies and is fifth leading cause of cancer-related death in Korea. It is difficult to expect early diagnosis or improvement in prognosis due to lack of specific early symptoms and effective diagnostic methods. Whereas cystic neoplasm of the pancreas is a rare type of pancreatic tumor, surgical resection provides good prognosis because of its low possibility of local invasion or distant metastasis. In case of pancreatic cystic tumor, radiologic differentiation between benign and malignant lesions is crucial for the selection of appropriate treatment and the prediction of prognosis. And ductal adenocarcinoma of pancreas presenting in cystic form is an uncommon type of cystic tumor, making it extremely rare among all pancreatic malignancies. We report two cases of atypical pancreatic ductal adenocarcinoma presenting as solid pseudopapillary tumor and intraductal papillary mucinous neoplasm, respectively.     

European experts consensus statement on cystic tumours of the pancreas

Cystic lesions of the pancreas are increasingly recognized. While some lesions show benign behaviour (serous cystic neoplasm), others have an unequivocal malignant potential (mucinous cystic neoplasm, branch- and main duct intraductal papillary mucinous neoplasm and solid pseudo-papillary neoplasm). European expert pancreatologists provide updated recommendations: diagnostic computerized tomography and/or magnetic resonance imaging are indicated in all patients with cystic lesion of the pancreas. Endoscopic ultrasound with cyst fluid analysis may be used but there is no evidence to suggest this as a routine diagnostic method. The role of pancreatoscopy remains to be established. Resection should be considered in all symptomatic lesions, in mucinous cystic neoplasm, main duct intraductal papillary mucinous neoplasm and solid pseudo-papillary neoplasm as well as in branch duct intraductal papillary mucinous neoplasm with mural nodules, dilated main pancreatic duct >6 mm and possibly if rapidly increasing in size. An oncological partial resection should be performed in main duct intraductal papillary mucinous neoplasm and in lesions with a suspicion of malignancy, otherwise organ preserving procedures may be considered. Frozen section of the transection margin in intraductal papillary mucinous neoplasm is suggested. Follow up after resection is recommended for intraductal papillary mucinous neoplasm, solid pseudo-papillary neoplasm and invasive cancer.     

WHAT KIND OF BENEFIT DO WE EXPECT FOR PERORAL PANCREATOSCOPY IN THE DIAGNOSIS OF INTRADUCTAL PAPILLARY MUCINOUS TUMOR OF THE PANCREAS?

Intraductal papillary mucinous tumor (IPMT) of the pancreas is characterized by slow growth and a relatively favorable prognosis, however, invasive cancer originating in an IPMT is associated with a poor prognosis. Although various parameters in imaging modalities have been advocated to differentiate between benign IPMN and malignant ones, it is not easy to obtain definite diagnosis based on these parameters. Peroral pancreatoscopy (POPS) allows a clear and direct visualization of the pancreatic duct, providing useful information regarding tumor nature in IPMT. The authors have studied the usefulness of POPS in the diagnosis of IPMT. Nevertheless, its usefulness is not necessarily widely accepted and the significance of POPS is still controversial. In this review, the authors intended to address the diagnostic value of POPS and to clarify its role in the diagnosis of IPMT. The authors think treatment of IPMT can be improved by introducing POPS because the determination of surgical procedure as well as the area of resection based on the preoperative diagnosis of the involvement of the main pancreatic duct and branch duct is inevitable.     

p53 protein expression in intraductal papillary mucinous tumors (IPMT) of the pancreas as an indicator of tumor malignancy

BACKGROUND/AIMS: Intraductal papillary mucinous tumors, as a cystic disease in the pancreas, clinically has a more indolent and favorable course than invasive ductal pancreas carcinoma. However, some cases of intraductal papillary mucinous tumors show invasive and rapid progression like ductal pancreas carcinoma and the prognosis of such patients is sometimes poor. In the current study, we carried out immunohistochemical staining of intraductal papillary mucinous tumor tissues for p53 and investigated whether positive staining indicates tumor malignancies and has a prognostic value for intraductal papillary mucinous tumors. METHODOLOGY: Nineteen (19) patients who underwent pancreatic resection under the diagnosis of intraductal papillary mucinous tumors at the Chiba University Hospital between April 1992 and December 1996 were studied. We performed immunohistochemical staining of p53 as well as of PCNA, Ki-67 and Bcl-2 using their respective antibodies. Pathological findings revealed that 9 cases were intraductal papillary adenoma, 9 were intraductal papillary adenocarcinoma, and one was invasive ductal papillary adenocarcinoma. RESULTS: p53 expression could only be detected in the 1 case with invasive ductal papillary adenocarcinoma. Significant association could not be found between histological features and immunohistochemical staining of PCNA, Ki-67 and Bcl-2. CONCLUSIONS: p53 protein expression could be detected after progression to invasive type of intraductal papillary mucinous tumors. The present results demonstrate that p53 expression might be an indicator of invasive progression in intraductal papillary mucinous tumors, and might represent a surgical indicator of intraductal papillary mucinous tumors.     

A case of intraductal papillary-mucinous carcinoma of the pancreas with the onset of acute pancreatitis

Intraductal papillary-mucinous carcinoma of the pancreas has been reported with increasing frequency. We report a case with intraductal papillary-mucinous carcinoma of the pancreas and discuss surgical treatment and current imaging modalities. A case with intraductal papillary-mucinous carcinoma was analyzed by radiological findings and clinical course. A 47-year-old man developed abdominal pain and nausea. Computed tomography showed a diffusely dilated main pancreatic duct. Duodenoscopy showed a patulous orifice of the pancreas with massive mucus secretion, but the pancreatic juice was not positive for malignant cells. Endoscopic retrograde cholangiopancreatography revealed a markedly dilated pancreatic duct extending from the body to the tail of the pancreas. Distal pancreatectomy was performed with splenectomy and lymph nodes dissection. Histopathological diagnosis was intraductal papillary-mucinous carcinoma. Endoscopic retrograde cholangiopancreatography is useful for diagnosing intraductal papillary mucin-producing tumors. To avoid unnecessary total pancreatectomy and preserve pancreatic function, intraoperative frozen section examination is widely available for the surgical treatment of intraductal papillary mucin-producing tumors.     

PERORAL PANCREATOSCOPY AND INTRADUCTAL ULTRASONOGRAPHY IN DETERMINING THE RESECTION LINES OF INTRADUCTAL PAPILLARY MUCINOUS TUMORS OF THE PANCREAS

In patients with malignant intraductal papillary–mucinous tumors (IPMT), the tumor spread along the main pancreatic duct is generally inspected as mural nodules within the ducts by peroral pancreatoscopy (POPS). Even the lower mural nodules including fish‐eggs‐like lesions and granular mucosa continued to the main taller mural nodules should be resected. Mural nodules along the main duct and cystic dilation of the branch ducts observed by intraductal ultrasonography (IDUS) are regarded as the tumor spread. Although POPS is superior to IDUS in identifying mural nodules along the main duct, POPS has limitations to detect mural nodules within the branch ducts. Therefore, the accuracy of the diagnosis by POPS is higher in main duct IPMT, whereas that by IDUS is higher in branch duct IPMT. These modalities should be performed as complementary tests in determining the resection lines preoperatively.     

Intraductal papillary-mucinous tumors of the pancreas

BACKGROUND/AIMS: To elucidate the risk of malignancy and the morphological alterations associated with malignancy. METHODOLOGY: Thirty cases of intraductal papillary-mucinous tumors and 5 papillary-mucinous carcinomas (invasive intraductal papillary-mucinous tumors) of the pancreas were clinicopathologically and histopathologically analyzed. RESULTS: The invasive carcinoma developed on the basis of severe dysplasia-carcinoma in situ changes and never from mild or moderate dysplasia changes. However, tumor cell projections of intraductal papillary-mucinous tumors encroached into the duct wall and/or the stroma introduced just beneath the epithelium and "intraductal" tumor cells sometimes came in direct contact with the "extraductal" connective tissues even in adenomas. The frankly invasive adenocarcinoma components of invasive intraductal papillary-mucinous tumors were characterized by the lack or poor formation of their own basement membrane and were usually surrounded by the extensive collagenous proliferation, desmoplastic reaction. Such stromal alterations never developed around the "extraductal" components of non-invasive intraductal papillary-mucinous tumors. CONCLUSIONS: The risk of malignancy for an individual intraductal papillary-mucinous tumor was increased with the degree of cellular and/or structural atypia. The desmoplastic reaction with poor formation of the basement membrane is the sine qua non of the "true invasion".