Suguru Yonezawa

An illustrated consensus on the classification of pancreatic intraepithelial neoplasia and intraductal papillary mucinous neoplasms

Invasive pancreatic ductal adenocarcinoma is an almost uniformly fatal disease. Several distinct noninvasive precursor lesions can give rise to invasive adenocarcinoma of the pancreas, and the prevention, detection, and treatment of these noninvasive lesions offers the potential to cure early pancreatic cancers. Noninvasive precursors of invasive ductal adenocarcinoma of the pancreas include pancreatic intraepithelial neoplasias (PanINs), intraductal papillary mucinous neoplasms (IPMNs), and mucinous cystic neoplasms. Diagnostic criteria, including a distinct ovarian-type stroma, and a consistent nomenclature are well established for mucinous cystic neoplasms. By contrast, consistent nomenclatures and diagnostic criteria have been more difficult to establish for PanINs and IPMNs. Because both PanINs and IPMNs consist of intraductal neoplastic proliferations of columnar, mucin-containing cells with a variable degree of papilla formation, the distinction between these two classes of precursor lesions remains problematic. Thus, considerable ambiguities still exist in the classification of noninvasive neoplasms in the pancreatic ducts. A meeting of international experts on precursor lesions of pancreatic cancer was held at The Johns Hopkins Hospital from August 18 to 19, 2003. The purpose of this meeting was to define an international acceptable set of diagnostic criteria for PanINs and IPMNs and to address a number of ambiguities that exist in the previously reported classification systems for these neoplasms. We present a consensus classification of the precursor lesions in the pancreatic ducts, PanINs and IPMNs.

Classification of types of intraductal papillary-mucinous neoplasm of the pancreas: a consensus study

Now that more than two decades have passed since the first reports of intraductal papillary-mucinous neoplasms (IPMNs), it has become clear that IPMN consists of a spectrum of neoplasms with both morphological and immunohistochemical variations. At a meeting of international experts on pancreatic precursor lesions held in 2003, it was agreed that a consensus classification of IPMN subtypes should be established to enable a more detailed analysis of the clinicopathological significance of the variations. Based on our experience and on information from the literature, we selected representative histological examples of IPMNs and defined a consensus nomenclature and criteria for classifying variants as distinctive IPMN subtypes including gastric type, intestinal type, pancreatobiliary type, and oncocytic type. These definitions can be used for further analyses of the clinicopathological significance of the variations of IPMN.

EXPRESSION OF MUCIN ANTIGENS IN HUMAN CANCERS AND ITS RELATIONSHIP WITH MALIGNANCY POTENTIAL

Mucins are high molecular weight glycoproteins having oligosaccharldes attached to the apomucin protein backbone by Gglycosidlc Inkages. Blochemical studies on the structures and the organ specificities of several much core proteine (MUC1‐MUC7) have been reported during the past several years. In the present study of pancreas and Intrahepatic bile duct tumors, MUCl mucin (membrane bound much detected by monoclonal antibody, DF3) was highly expressed in Invasive ductal carcinomas of the pancreas (IDC) and Invasive cholangiocarcinomas of the liver (CC), which show Invasive growth and a poor prognosis, but it was rarely expressed in intraductal papillary mucinous tumors of the pancreas (IPMT) and bile duct cystadenocarcinomas of the liver (BDCC), which show a favorable prognosis. In contrast, MUC2 mucin (intestinal type secretory much detected by polyclonal antibody, anti‐MRP) was rarely expressed in IDC and ICC, whereas it was highly expressed in IPMT and BDCC. The results suggest that the differences in the expression of MUC1 and MUC2 mucins are a useful prognostic Indicator of mailgnancy potential in the neoplasms of the pancreas and intrahepatic bile duct. Moreover, the expression of MUC1 and MUC2 mucins was a useful Indicator of the malignancy potential of tumors derived from other organs, such as the ampulla of Vater, stomach and breast. In another study on the expression of several MUC1 much antigens with different patterns of glycosylatlon, sialylated‐MUC1 mucin detected by monoclonal antibody, MY. 1E12, was found to be expressed in all the Invasive carcinomas (IDC and ICC) but was not frequently seen in the non‐invasive type tumors (IPMT and BDCC), although the other types of MUC1 mucins did not show such contrast between the invasive and non‐invasive type turnors. The results suggest that sialylation of MUC1 mucin is associated with Invasive growth of neoplasms. In contrast, our study of the expression of MUC2 mRNA (transcript of intestinal type much) and MUC5AC mRNA (transcript of gastric type much) by in situ hybridization in the tumors of the pancreas and Intrahepatic bile duct found that the non‐Invasive type tumors (IPMT and BDCC) synthesize MUC2 mRNA and MUC5AC mRNA, whereas most of the Invasive carcinomas (IDC and ICC) do not. Furthermore, patients positive for MUC2 mRNA or MUC5AC mRNA expression in the tumors showed significantly better survival than the patients with no expression. The production of MUC2 or MUC5AC, an abundant extracellular intestinal or gastric type secretary much with high viscosity may be correlated, by a majority of the non‐Invasive type tumors, with the expansive growth of the tumors that display lower levels of invasion and metastasis.

Prognostic relevance of morphological types of intraductal papillary mucinous neoplasms of the pancreas

Objective The clinicopathological significance of four morphological types of intraductal papillary mucinous neoplasms of the pancreas (IPMNs; gastric, intestinal, pancreatobiliary and oncocytic) was assessed. Design Retrospective multicentre analysis of 283 surgically resected IPMNs. Results Of the 283 IPMNs, 139 were of the gastric type, 101 were intestinal, 19 were pancreatobiliary and 24 were oncocytic. These types were significantly associated with clinicopathological factors including sex (p=0.0032), age (p=0.00924), ectatic duct size (p=0.0245), detection of mural nodules (p=4.09×10−6), histological grade (p<2.20×10−16), macroscopic types with differential involvement of the pancreatic duct system (p=3.91×10−5), invasive phenotypes (p=3.34×10−12), stage (p<2.20×10−16) and recurrence (p=0.00574). Kaplan–Meier analysis showed significant differences in patient survival by morphological type (p=5.24×10−6). Survival rates at 5 and 10 years, respectively, were 0.937 (95% CI 0.892 to 0.984) for patients with gastric-type IPMNs; 0.886 (95% CI 0.813 to 0.965) and 0.685 (95% CI 0.553 to 0.849) for those with intestinal-type IPMNs; 0.839 (95% CI 0.684 to 1.000) and 0.734 (95% CI 0.526 to 1.000) for those with oncocytic-type IPMNs; and 0.520 (95% CI 0.298 to 0.909) and undetermined for those with pancreatobiliary-type IPMNs. Analysis by the Cox proportional hazards model comparing prognostic risks determined by stage and the morphological and macroscopic types indicated that staging was the most significant predictor of survival (p=3.68×10−8) followed by the morphological type (p=0.0435). Furthermore, the morphological type remained a significant predictor in a subcohort of invasive cases (p=0.0089). Conclusion In this multicentre retrospective analysis, the morphological type of IPMN appears to be an independent predictor of patient prognosis.

New classification of pancreatic intraductal papillary–mucinous tumour by mucin expression: its relationship with potential for malignancy

In previous studies of the expression of MUC1 (membrane‐bound type mucin) and MUC2 (intestinal type secretory mucin) in pancreatic tumours, invasive ductal carcinoma (IDC) usually showed MUC1+ and MUC2− expression, whereas intraductal papillary–mucinous tumour (IPMT) showed MUC1− and MUC2+ expression. Recently, however, many IPMTs have been collected, a considerable number of which have shown MUC1− and MUC2− expression. In the present study, the clinicopathological features were examined of 18 IPMTs with MUC2+ and 32 IPMTs with MUC2−, and their potential for malignancy was compared. Most of the IPMTs with MUC2+ were composed of dark columnar cells, whereas most of the IPMTs with MUC2− were composed of clear columnar cells. The incidence of carcinomatous change and invasive proliferation of the carcinoma in the MUC2+ tumours was significantly higher than in the MUC2− tumours. The clinical outcome for the patients with IPMT showing the MUC2+ pattern tended to be worse than for those with IPMT showing the MUC2− pattern, although the overall outcome for the two types of IPMT was significantly better than for those with IDC. Because of the differences in mucin expression pattern, morphological appearance and potential for malignancy between the two types of IPMT, we believe that they belong to different neoplastic lineages and that it may be reasonable to classify them as different entities, although the WHO classification contains a single clinicopathological entity of IPMT forming an adenoma–carcinoma sequence. In conclusion, our classification of IPMTs by MUC2 expression pattern may be of value in the better assessment of the biological behaviour of IPMTs and their potential for malignancy. Copyright

Pathologic Features of Mucin-producing Bile Duct Tumors: Two Histopathologic Categories as Counterparts of Pancreatic Intraductal Papillary-mucinous Neoplasms

Tumors with clinically recognizable mucin production arising from bile duct, “mucin-producing bile duct tumors (MPBTs),” have not been studied yet for their pathologic features and classification in details. The clinical findings of MPBT have a lot of similarities to those of pancreatic intraductal papillary-mucinous neoplasm. In the present study, we examined 30 MPBTs and classified them into two distinct morphologic categories: 22 cases of “columnar type” composed of pseudostratified columnar cells with basophilic cytoplasm and columnar nuclei and 8 cases of “cuboidal type” composed of pancreaticobiliary and/or oncocytic pattern. Pancreaticobiliary pattern showed abundantly branched papillae lined by acidophilic cuboidal cells with round nuclei, whereas oncocytic pattern was characterized by intraepithelial lumina and cribriform pattern composed of abundant oxyphilic cells with round nuclei, and these patterns overlapped frequently. There were significant differences in the clinicopathologic findings including macroscopic findings, morphometric data, mucin expression profiles (MUC2 expression in columnar type and MUC6 expression in cuboidal type), and cell proliferative activities between columnar type and cuboidal type. Patients with columnar type showed significantly poorer survival than those with cuboidal type. We concluded that columnar type and cuboidal type of MBPTs belong to different lineage of neoplasm and that they are counterparts of “intestinal type” and “pancreaticobiliary type” of pancreatic intraductal papillary-mucinous neoplasm, respectively.

Gene expression of gastric type mucin (MUC5AC) in pancreatic tumors: Its relationship with the biological behavior of the tumor

Previously it has been found that the MUC2 gene for intestinal type secretory mucin is highly expressed in intraductal papillary mucinous tumors (IPMT), which are characterized by non‐invasive growth and a favorable outcome. In contrast, MUC2 mRNA is rarely expressed in invasive ductal carcinomas (IDC), which have poor outcomes. The gastric type secretory mucin, MUC5AC, is strongly expressed in the surface mucous cells of gastric mucosa. As both MUC2 and MUC5AC mucins share the characteristics of forming highly viscous gels, it is expected that not only MUC2 mucin expression but also MUC5AC mucin expression may be associated with a favorable prognosis in patients with pancreatic tumors. MUC5AC mucin gene expression was examined in 24 cases of IPMT and 38 cases of IDC by in situ hybridization using a digoxigenin‐labeled oligonucleotide. The results were compared with MUC2 mucin gene expression. Neither MUC5AC mRNA nor MUC2 mRNA was detected in normal pancreatic tissues. MUC5AC mRNA was expressed in 20 of 24 cases of IPMT (83%) and in five of 38 cases of IDC (13%). In contrast, MUC2 mRNA was expressed in 14 of 24 cases of IPMT (58%) and in none of the 38 cases of IDC (0%). The expression rates of MUC5AC mRNA and MUC2 mRNA in IPMT were significantly higher than those in IDC (P < 0.001, respectively). Intraductal papillary mucinous tumors are characterized by three histological types: (i) villous dark cell type; (ii) papillary clear cell type; and (iii) compact cell type. The villous dark cell type generally expressed both MUC5AC+ and MUC2+ genes. Alternatively, the papillary clear cell type and the compact cell type usually showed MUC5AC+ and MUC2− expression. Patients with MUC5AC mRNA expression had a significantly better survival prognosis than those with no MUC5AC mRNA expression (P < 0.005). In conclusion, MUC5AC gene expression occurs in a majority of IPMT cases, even in those with no MUC2 production. MUC5AC expression can be correlated with tumors that demonstrate an expansive growth pattern and lower levels of invasion and metastasis.

MUC4 expression is a novel prognostic factor in patients with invasive ductal carcinoma of the pancreas

Background: Many patients with invasive ductal carcinoma of the pancreas (IDC) have a poor outcome. MUC4 expression has been implicated as a marker for diagnosis and progression of IDC, but there are no studies of the relation between MUC4 expression and patient prognosis in IDC. Aims: To investigate the prognostic significance of MUC4 expression in IDC. Methods: The expression profiles of MUC4, ErbB2, p27, and MUC1 were investigated in IDC tissues from 135 patients by means of immunohistochemistry. Results: MUC4 was expressed in 43 of the 135 patients with IDC (31.9%). The survival of 21 patients with high MUC4 expression (>20% of neoplastic cells stained) was significantly worse than that of the 114 patients with low MUC4 expression (<20% of neoplastic cells stained) (p  =  0.0043). Univariate analysis showed that high MUC4 expression (p  =  0.0061), large primary tumour status (>T2) (p  =  0.0436), distant metastasis (p  =  0.0383), lymphatic invasion (p  =  0.0243), and surgical margins (p  =  0.0333) were significant risk factors affecting the outcome of patients with IDC. Backward stepwise multivariate analysis showed that MUC4 expression (p  =  0.0121), lymph node metastasis (p  =  0.0245), and lymphatic invasion (p  =  0.0239) were significant independent risk factors. ErbB2, p27, and MUC1 were not independent risk factors. Conclusions: This study shows that MUC4 expression in IDC is a new independent factor for poor prognosis and predicts the outcome of patients with IDC.

MUC2 gene expression is found in noninvasive tumors but not in invasive tumors of the pancreas and liver: Its close relationship with prognosis of the patients☆

We have previously reported that MUC2 apomucin was highly expressed in noninvasive tumors of the pancreas (intraductal papillary tumor [IdPT]) and liver (bile duct cystadenocarcinoma [BdCC]), which show more favorable outcomes than invasive carcinomas. In contrast, MUC2 was rarely expressed in invasive carcinomas of the pancreas (invasive ductal carcinoma [IDC]) and the liver (invasive cholangiocarcinoma [ICC]). In the present study, we examined localization of MUC2 messenger RNA (MUC2 mRNA) by using a complementary DNA (cDNA) probe for the MUC2 tandem repeat for in situ hybridization (pHAM1). Localization of MUC2 apomucin was determined by using an antibody directed against MUC2 apomucin (anti-MRP) for immunohistochemistry study. Eleven IdPTs and 10 IDCs of the pancreas, and 8 BdCC and 8 ICCs of the liver were examined. Nine (82%) of 11 IdPTs showed positive expression of MUC2 mRNA in the neoplastic cells, whereas none (0%) of the IDCs showed expression of MUC2 mRNA. Six (75%) of the 8 BdCCs showed positive expression of MUC2 mRNA in the neoplastic cells, whereas none (0%) of the 8 ICCs showed expression of MUC2 mRNA. The localization of MUC2 mRNA and that of MUC2 apomucin usually coincided, although a few cases (1 IDC, 1 BdCC, and 1 ICC) showed focal expression of MUC2 apomucin despite the absence of detectable MUC2 mRNA. These results indicate that the expression of MUC2 apomucin in IdPTs and BdCCs correlates with expression of MUC2 mRNA. In both patient groups with pancreatic tumors and hepatic tumors, patients with positive MUC2 mRNA expression in the tumors showed significantly better survival than those with negative MUC2 mRNA expression in the tumors. The production of MUC2, an abundant extracellular mucin, by most IdPTs and BdCCs may be correlated with tumors that display lower levels of invasion and metastasis.

Immunohistochemical study of mucin carbohydrates and core proteins in human ovarian tumors

Many of the cancer-associated antigens recently have been identified as mucin antigens. However, there are no detailed studies describing the expression of carbohydrates and core proteins of mucin antigens in ovarian tumors. In this study we examined the expression of carbohydrate antigens, which are associated with the earliest steps in mucin glycosylation (Tn and sialosyl-Tn), and the expression of the mucin core protein antigens associated with the MUC1 gene product (mammary-type apomucin) and the MUC2 gene product (intestinal-type apomucin) in 123 ovarian epithelial (mucinous and serous) tumors. In normal ovarian tissues neither Tn, sialosyl-Tn, nor intestinal-MRP antigens (MUC2 gene product) were expressed, except for positive sialosyl-Tn staining of stromal capillaries, while the MUC1 gene product, DF3 antigen, was expressed in the cell apex of the germinal coelomic epithelium when it had plump, slightly elongated, or pseudostratified nuclei. In the benign adenomas Tn and sialosyl-Tn antigens were detected in a small number of mucinous adenomas and rarely in serous adenomas. In contrast, expression of both Tn and sialosyl-Tn antigens was observed in all the adenocarcinomas and in a considerable number of borderline malignancies. DF3 antigen was expressed in many benign serous tumors but not so frequently in benign mucinous tumors; however, it was frequently expressed in the adenocarcinomas and borderline malignancies of both mucinous and serous types. Intestinal-MRP antigen expression increased with the transition of the mucinous tumors from a benign to malignant state, although it was never detected in the serous tumors. Coexpression of DF3 and intestinal-MRP antigens was seen in borderline malignancies and carcinomas of the mucinous tumors. In conclusion, simultaneous expression of Tn and sialosyl-Tn antigens is a highly effective tumor marker in both mucinous and serous tumors of the ovary. Coexpression of DF3 and intestinal-MRP antigens may indicate the malignant potential of ovarian mucinous tumors.