Clinicopathological features of pancreatic intraepithelial neoplasias and their relationship to intraductal papillary-mucinous tumors

Pancreatic intraepithelial neoplasia (PanIN) is a recently proposed nomenclature for putative precursor lesions of pancreatic cancer, which are designated as PanIN-1 through -3 according to their increasing grade of dysplasia. A stepwise progression model of PanINs has been proposed, and multistep genetic alterations in PanINs are being investigated. PanIN-1A and PanIN-1B may remain unchanged for a long period. PanIN-3 potentially progresses toward invasive ductal carcinoma (IDC), and there are several case reports suggesting such progression. In these reported patients, PanIN-3 was found in specimens from partial pancreatectomies, and IDC manifested in the pancreatic remnant 17 months to 29 years after the surgery. We describe herein a patient with PanIN-3, in whom IDC manifested in the distal remnant pancreas 69 months after segmental pancreatectomy. Of the reported cases, including the present one, four of the patients were male and three were female, and the age at the first operation ranged from 46 to 70 years. Intraductal papillary-mucinous tumor (IPMT) is an entity that is distinct from PanIN. However, IPMTs of small size resemble PanINs morphologically. Loss of Dpc4 expression has been reported in the invasive component of IPMT, as well as in PanIN-3 and IDC. Analysis of mucin expression patterns has been reported, suggesting that, in practice, MUC1-positive MUC2-negative IPMTs may not be distinguishable from PanINs. There may be overlapping lesions between PanINs and IPMTs. Should the paradigm of the ductal origin of IDC be accepted, PanINs and a fraction of IPMTs would represent precursors of IDC.     

The pathology of ductal-type pancreatic carcinomas and pancreatic intraepithelial neoplasia: Insights for clinicians

The phenotypic classification of pancreatic neoplasms is based on their cellular lineage. Thus, tumors with a ductal, acinar, and endocrine phenotype can be distinguished. Most pancreatic neoplasms show a ductal phenotype and can be classified as ductal adenocarcinomas. Less common tumors with a ductal phenotype are the variants of ductal adenocarcinoma, intraductal papillary mucinous neoplasm (including colloid carcinoma), mucinous cystic neoplasm, medullary carcinoma, and other rare tumors. Ductal adenocarcinomas most likely develop from ductal proliferative lesions arising in the pancreatic duct system. A recently adopted classification system for these lesions distinguishes between three grades of pancreatic intraepithelial neoplasia (PanIN). Molecular studies have revealed that PanIN-2 and PanIN-3 lesions represent a distinct step toward invasive carcinoma.     

Evaluation of pancreatic intraepithelial neoplasia and mucin expression in normal pancreata

Background/purpose

It has been suggested that pancreatic ductal adenocarcinoma (PDAC) and pancreatic intraepithelial neoplasia (PanIN) are closely related, but several reports indicate PanIN lesions can also be found in normal pancreata (normal PanINs). We examined differences in mucin expression between normal PanIN lesions and PanINs in PDACs (PDAC PanINs).

Methods

We examined 54 autopsied normal pancreata and eight autopsied PDACs for PanIN lesions; graded the pancreata specimens as PanIN-1A (non-papillary hyperplasia), PanIN-1B (papillary hyperplasia), PanIN-2 (atypical hyperplasia) or PanIN-3 (carcinoma in situ); and tested the PanIN lesions for expression of MUC1 (pan-epithelial membrane-associated mucin) and MUC5AC (gastric secretory mucin) which were both previously detected in PDACs.

Results

In normal PanIN-1A, PanIN-1B and PanIN-2 specimens, MUC1 was expressed in 2.8, 10.5 and 9.1%, respectively, compared to 19.1, 27.6 and 13.0% in PDAC PanIN-1A, PanIN-1B and PanIN-2 specimens, respectively. MUC5AC was expressed in 41.0, 65.7 and 36.4% of normal PanIN-1A, PanIN-1B and PanIN-2 specimens, respectively, and in 80.9, 75.8 and 78.3% of PDAC PanIN-1A, PanIN-1B and PanIN-2 specimens, respectively. Differences in the frequency of MUC1 expression were significant between normal and PDAC PanIN-1A (p?<?0.0001) and PanIN-1B (p?<?0.05); and differences in the frequency of MUC5AC expression were significant between normal and PDAC PanIN-1A (p?<?0.0001) and PanIN-2 (p?<?0.05).

Conclusions

Normal PanIN and PDAC PanIN lesions differed in the rates of MUC1 and MUC5AC expression.     

Update on the pathology and genetics of exocrine pancreatic tumors with ductal phenotype: precursor lesions and new tumor entities

The majority of pancreatic neoplasms show a ductal phenotype and can be classified as ductal adenocarcinomas. Pancreatic duct lesions have been discussed as tumor precursors. This review presents a recently adopted standard system for these lesions which distinguishes among three grades of pancreatic intraepithelial neoplasia (PanIN). Molecular studies revealed that PanIN-2 and PanIN-3 lesions represent a distinct step towards invasive carcinoma. Another focus of the review is the advances that have been made in the further immunohistochemical and molecular characterization of special pancreatic neoplasms showing a ductal phenotype, such as undifferentiated carcinoma, mucinous noncystic (colloid) carcinoma, intraductal papillary mucinous neoplasm, mucinous cystic neoplasm, medullary carcinoma, and other rare tumors.     

Serine protease inhibitor Kazal type 1 and epidermal growth factor receptor are expressed in pancreatic tubular adenocarcinoma, intraductal papillary mucinous neoplasm, and pancreatic intraepithelial neoplasia

Background

Serine protease inhibitor Kazal type 1 (SPINK1) is expressed in normal human pancreatic acinar cells and in a variety of tumors, and binds to the epidermal growth factor receptor (EGFR), mediating cell proliferation through the mitogen-activated protein kinase cascade in pancreatic cancer cell lines. Here, we aimed to assess SPINK1 and EGFR expression in various neoplastic lesions, including tissues demonstrating precancerous changes.

Methods

Surgical specimens of pancreatic ductal adenocarcinoma (n = 23), intraductal papillary mucinous neoplasm (IPMN; n = 21), pancreatic neoplasms other than ductal adenocarcinoma (n = 8), chronic pancreatitis (n = 11), and pancreatic intraepithelial neoplasia (PanIN) lesions within the resected specimens were analyzed immunohistochemically for SPINK1 and EGFR expression.

Results

Sixty-five PanIN-1A, 32 PanIN-1B, 17 PanIN-2, and 6 PanIN-3 were identified. Both SPINK1 and EGFR were expressed in almost all PanIN lesions. All tubular ductal adenocarcinoma, IPMN, and mucinous cystadenocarcinoma samples (neoplasms of ductal origin) expressed SPINK1, whereas acinar cell carcinoma, anaplastic carcinoma, adenosquamous carcinoma, insulinoma, and islet cell carcinoma did not. EGFR was expressed in 87 % of tubular adenocarcinoma and 48 % of IPMN lesions. Among IPMN lesions, malignant lesions (IPMC) expressed EGFR more often than benign lesions (IPMA) did. Scattered expression of EGFR was observed in normal pancreatic ducts and within the tubular complex within chronic pancreatitis lesions.

Conclusions

These results indicate that SPINK1 plays a role as a growth factor, signaling through the EGFR pathway in pancreatic ductal adenocarcinoma and neoplasms, and that the EGFR is involved in the malignant transformation of IPMN.     

Aberrant expression of MUC5AC and MUC6 gastric mucins and sialyl Tn antigen in intraepithelial neoplasms of the pancreas

BACKGROUND & AIMS: It has recently been suggested that infiltrating adenocarcinoma of the pancreas arises from histologically well-defined precursor ductal lesions called pancreatic intraepithelial neoplasia (PanIN-1A, -1B, -2, and -3). This study examined alterations in the pattern and the level of expression of several mucin genes (MUC1, MUC2, MUC5AC, and MUC6) and mucin-associated tumor antigens (Nd2 and sialyl Tn) in these precursor lesions. METHODS: We examined 139 PanINs and 68 infiltrating ductal adenocarcinomas of the pancreas by using immunohistochemistry and in situ hybridization methods. RESULTS: Overexpression of MUC1, a pan-epithelial mucin, and MUC6, a pyloric-gland mucin, and de novo expression of MUC5AC, a gastric foveolar mucin, was observed in all stages of PanINs and invasive ductal adenocarcinoma. In contrast, the expression of mucin-associated carbohydrate antigen, sialyl Tn, was markedly increased only in PanlN-3 and invasive ductal adenocarcinoma. In addition, a decrease in the expression of these mucin-associated peptide and carbohydrate antigens was correlated with the degree of differentiation of the tumor. CONCLUSIONS: Expression of both gastric-foveolar and pyloric-gland mucin in PanINs is an early event, whereas sialyl Tn expression is a late event in the recently defined progression model of pancreatic carcinogenesis. This altered mucin gene expression provides new insight into the role of cell lineage-associated metaplasia in pancreatic carcinogenesis.     

Current understanding of precursors to pancreatic cancer

Precursors to pancreatic cancer have been investigated for a century. Previous studies have revealed three distinct precursors,i.e. mucinous cystic neoplasm (MCN), intraductal papillary mucinous neoplasm (IPMN), and pancreatic intraepithelial neoplasia (PanIN), harboring identical or similar genetic alterations as does invasive pancreatic carcinoma. The current understanding of precursors to pancreatic cancer can be illustrated by progressive pathways from noninvasive MCN, IPMN, and PanIN toward invasive carcinoma. MCNs consist of ovarian‐type stroma and epithelial lining with varying grades of atypia, and are occasionally associated with invasive adenocarcinoma. The epithelium of noninvasive IPMNs shows a variety of different directions of differentiation, including gastric, intestinal, pancreatobiliary (PB), and oncocytic types. IPMNs can also harbor varying grades of architectural and cytologic atypia. IPMNs confined to branch ducts are mostly the gastric type, and IPMNs involving the main ducts are often intestinal type, while PB and oncocytic types are rare. Small (<1 cm) IPMNs of the gastric type are not always morphologically distinguishable from low‐grade PanINs. Mucin expression profiles suggest intestinal‐type IPMNs progress to mucinous noncystic (colloid) carcinoma, while PB‐type IPMNs progress toward ductal adenocarcinoma. It is a well‐described paradigm that PanIN lesions progress toward ductal adenocarcinoma through step‐wise genetic alterations. The activation of Hedgehog and Notch signaling pathways in PanIN lesions as well as in pancreatic adenocarcinoma suggest that developmental pathways may be disregulated during carcinogenesis of the pancreas. Further study is needed to elucidate the pathways from precursors toward invasive carcinoma of the pancreas.     

Proliferative activity in pancreatic intraepithelial neoplasias of chronic pancreatitis resection specimens: detection of a high-risk lesion

Patients with chronic pancreatitis have a markedly increased risk of pancreatic cancer compared with general population. Mechanism of the increased risk is not completely known. The current progression model for pancreatic ductal adenocarcinoma proposes the progression from normal ductal epithelium through a series of lesions called pancreatic intraepithelial neoplasias (PanINs) to invasive cancer. These lesions are frequently seen in chronic pancreatitis tissue. Proliferative activity in PanINs of chronic pancreatitis tissue has not been separately studied using the current nomenclature. Our study included 36 chronic pancreatitis resection specimens. A total number of 106 PanINs found within 32 resection specimens was histologically graded and then immunolabeled using a monoclonal antibody against Ki-67 that is expressed in dividing cells. The Ki-67 labeling indices in the increasing grades of PanINs were counted with following results: PanIN-1A, 0.77%; PanIN-1B, 3.26%; PanIN-2, 14.68%; and PanIN-3, 25.4%. The difference in Ki-67 labeling indices among these types of lesions was statistically significant (p<0.001, t-test). These results correlate with known genetic alterations found in chronic pancreatitis, especially with p16 inactivation that was recently described in PanINs arising in patients with chronic pancreatitis. Moreover, our findings support the currently accepted pancreatic progression model and Ki-67 immunohistochemistry might represent an efficient tool for an identification of a high-risk lesion.     

APC蛋白在胰腺癌及其癌前病变中的表达差异分析

背景：APC基因突变致Wnt／β-catenin信号通路异常活化可促进肿瘤发生。目的：分析APC蛋白在胰腺导管腺癌（PDAC）和胰腺癌前病变中的表达差异,探讨APC在PDAC发生中的作用。方法：以免疫组化方法检测APC蛋白在正常胰腺、胰腺上皮内瘤变（PanINs）、胰腺导管内乳头状黏液性肿瘤（IPMNs）、PDAC中的表达,分析其在PanIN-1、-2、-3、IPMN腺瘤（IPMA）、IPMN交界性肿瘤（IPMB）、IPMN腺癌（IPMC）、PDAC中的表达差异,以及APC蛋白表达与PDAC临床病理特征和患者预后的关系。结果：正常胰腺导管上皮APC表达阴性。由PanIN-1、PanIN-2至PanIN-3,APC免疫组化评分（IHCS）逐渐增高（P〈0．05）,PanIN-1APC阳性表达率显著低于PanIN-2、PanIN-3（P〈0．05）;IPMA、IPMB、IPMC间APCIHCS和APC阳性表达率均无明显差异。APC在PDAC和IPMNs中的表达具有明显不均一性,PDAC的APCIHCS和APC阳性表达率均显著低于各级别PanINs（P〈0．05）,与各级别IPMNs无明显差异。APC阳性表达与PDAC患者术后生存期短显著相关（P=0．003）。结论：APC蛋白表达异常是PDAC发生过程中的早期事件,其表达阳性提示患者预后不良。APC在胰腺癌中的具体作用机制有待进一步研究。     

Biological similarities and differences between pancreatic intraepithelial neoplasias and intraductal papillary mucinous neoplasms

BACKGROUND: Ever since the classification of pancreatic intraepithelial neoplasia (PanIN) was published, studies on the precursor lesions of pancreatic cancer have been advancing along a new directions, using standardized terminology. There are few studies that have examined the biological differences between PanIN and intraductal papillary mucinous neoplasm (IPMN) in detail. AIMS: PanIN and IPMN, which are similar in morphology, were compared using various indicators, with the aim of identifying the similarities and differences between the two. METHODOLOGY: A total of 46 PanINs and 37 ducts with IPMN were identified in 19 patients with invasive ductal carcinoma and 18 patients with IPMN. These PanINs and IPMNs were examined immunohistologically with respect to the expression patterns of HER2/neu, DPC4/Smad4, Akt/PKB, p53, cyclin A, Ki67, MUC1, and MUC2. RESULTS: Significant differences in the expression of MUC1 and MUC2 were observed between IPMNadenoma and PanIN-2 and between CIS and PanIN-3 (MUC1: p = 0.001 and p = 0.005, respectively; MUC2: p = 0.002 and p < 0.001, respectively). A significant difference in the p53 expression level was also observed between CIS and PanIN-3 (p = 0.015). CONCLUSIONS: In both IPMN and PanIN, the grade of atypism increased with increasing expression of HER2/neu, DPC4/Smad4, and Akt/PKB, along with progression in the process of multistage carcinogenesis. Although the expression levels of these factors reflected the grade of atypism, they did not reflect any differences in the grade of biological malignancy between IPMN and PanIN. On the other hand, MUC1 and MUC2 may serve as indicators of the direction of differentiation, i.e., either progression to IDAC or IPMN. Positivity for MUC1 was believed to suggest differentiation into IDAC, and positivity for MUC2 appeared to be indicative of differentiation into IPMN. Such indication of the direction of differentiation seemed to appear in PanIN1-2, even before abnormalities of HER2/neu, Akt/PKB, DPC4/Smad4, p53, and cyclin A expression began to be detected.     

胰腺导管腺癌、慢性胰腺炎及正常胰腺组织中胰腺上皮内瘤变的比较研究

目的探讨胰腺导管腺癌、慢性胰腺炎和正常胰腺组织中各级别PanIN的发生率以及与临床病理学参数间的关系。方法回顾性研究长海医院2001年1月-2003年12月间外科切除和同期尸检获得的250例胰腺标本中PanIN的发生情况,并联系临床病理指标进行相关分析。结果250例胰腺标本中,有156例存在PanIN病变,发生率62.4％。其中,胰腺导管腺癌、慢性胰腺炎和正常胰腺组织中PanIN的发生率分别为75.6％、46.0％和30.0％,胰腺导管腺癌PanIN发生率明显高于慢性胰腺炎及正常胰腺组织(P<0.01);慢性胰腺炎中高级别PanIN发生率明显高于正常胰腺组织(P<0.05)。PanIN-3仅在胰腺导管腺癌和慢性胰腺炎中见到。胰腺导管腺癌中,有烟酒嗜好和(或)糖尿病者高级别PanIN的发生率53.7％,明显高于对照组29.4％(P<0.01)。PanIN的发生率以61-70岁年龄组为最高。结论胰腺导管腺癌、慢性胰腺炎和正常胰腺组织中PanIN的发生率逐渐增加,程度逐渐加重,支持胰腺癌发生的分子模型。     

Notch and Kras reprogram pancreatic acinar cells to ductal intraepithelial neoplasia

Efforts to model pancreatic cancer in mice have focused on mimicking genetic changes found in the human disease, particularly the activating KRAS mutations that occur in pancreatic tumors and their putative precursors, pancreatic intraepithelial neoplasia (PanIN). Although activated mouse Kras mutations induce PanIN lesions similar to those of human, only a small minority of cells that express mutant Kras go on to form PanINs. The basis for this selective response is unknown, and it is similarly unknown what cell types in the mature pancreas actually contribute to PanINs. One clue comes from the fact that PanINs, unlike most cells in the adult pancreas, exhibit active Notch signaling. We hypothesize that Notch, which inhibits differentiation in the embryonic pancreas, contributes to PanIN formation by abrogating the normal differentiation program of tumor-initiating cells. Through conditional expression in the mouse pancreas, we find dramatic synergy between activated Notch and Kras in inducing PanIN formation. Furthermore, we find that Kras activation in mature acinar cells induces PanIN lesions identical to those seen upon ubiquitous Kras activation, and that Notch promotes both initiation and dysplastic progression of these acinar-derived PanINs, albeit short of invasive adenocarcinoma. At the cellular level, Notch/Kras coactivation promotes rapid reprogramming of acinar cells to a duct-like phenotype, providing an explanation for how a characteristically ductal tumor can arise from nonductal acinar cells.     

Pancreatic intraepithelial neoplasia

Great efforts have been devoted to detecting preinvasive precursors to ductal carcinoma of the pancreas in the hope of improving the currently bleak prognosis of invasive pancreatic cancer. Intensive investigations of the pancreas have led to the recognition of intraductal papillary mucinous neoplasms (IPMNs) and the detection of preinvasive precursors to conventional ductal carcinoma. The pancreatic intraepithelial neoplasia (PanIN) nomenclature for precursor lesions of ductal carcinoma was developed at the "Pancreatic Cancer Think Tank" held in the United States in 1999. However, some reports of precursor lesions have suggested that these definitions do not encompass the full spectrum of precursors of ductal carcinoma, and these issues were the subject of the "Forum on Carcinoma In Situ of the Pancreas" held in Japan in 2002. After this forum, it became clear that the existing definitions of PanINs needed to be revised and expanded. Both participants of the Pancreatic Cancer Think Tank and the Forum gathered together at a meeting on precursor lesions of pancreatic cancer in 2003, and an international consensus on the diagnostic criteria for PanINs and IPMNs was created. We describe herein the current understanding of precursor lesions of pancreatic cancer.     

Pancreatic intraepithelial neoplasia-3 with localized acute pancreatitis in the main pancreatic duct

Pancreatic intraepithelial neoplasia (PanIN) is one of the most important issues for the early detection of pancreatic ductal adenocarcinoma. In particular, PanIN-3 is recognized as a precancerous lesion, e.g., carcinoma in situ, high-grade dysplasia, and severe dysplasia. We report a rare, completely resected case of PanIN-3 in the main pancreatic duct (MPD) detected from localized pancreatitis. A 63-year-old man developed upper abdominal pain with hyperamylasemia. He underwent distal pancreatectomy soon after recovery because an abnormal narrow segment, suggesting PanIN, was identified in the pancreatic body by endoscopic retrograde cholangiopancreatography. Histopathological findings revealed a PanIN-3 located in the MPD that could be resected completely. This finding suggests that if unidentified localized pancreatitis develops, we should carefully examine the fine structural changes in the MPD.     

Relationship between K-ras mutation and the expression of p21WAF1/CIP1 and p53 in chronic pancreatitis and pancreatic adenocarcinoma

Overexpression of p21WAF1/CIP1 was recently described as an early event in the development of pancreatic intraepithelial neoplasia. Since activating K-ras mutations are described in more than 80% of pancreatic cancers and are known to increase intracellular levels of p21WAF1/CIP1 in experimental models, the possible role of activating K-ras mutations in an induction of the p21WAF1/CIP1 expression was investigated in our study. We examined 71 surgical specimens, 29 of chronic pancreatitis and 42 of invasive ductal adenocarcinoma both having a large spectrum of PanIN (pancreatic intraepithelial neoplasia) lesions. Expression of p53 and p21WAF1/CIP1 was examined immunohistochemically and codon 12 K-ras mutational analysis was performed using the very sensitive mutant-enriched PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) analysis. Our study demonstrated the overexpression of p21WAF1/CIP1 as an early event in the development of pancreatic intraepithelial neoplasia in the group of chronic pancreatitis and invasive adenocarcinoma as well. Overexpression of p21WAF1/CIP1 increased progressively from normal ducts through the spectrum of PanIN lesions to invasive carcinomas. The p53 overexpression increased again progressively according to the severity of the lesion and seems to be a later event in the development of pancreatic intraepithelial neoplasia if compared to p21WAF1/CIP1 expression. Our results confirmed also the possible p53 independent p21WAF1/CIP1 expression in some PanIN2, PanIN3 lesions and invasive carcinomas. K-ras mutations were not revealed in samples with only low grade PanIN lesions (PanIN1a and PanIN1b). K-ras mutations were detected in 69,4% adenocarcinomas and in only one case of chronic pancreatitis. Two codon 12 K-ras positive pancreatic carcinomas showed K-ras mutations in the surrounding normal pancreatic tissue. In adenocarcinomas, no statistically significant correlation was found between K-ras mutational status and p21WAF1/CIP1 and p53 expression, respectively. The possible role of activating K-ras mutations in an induction of p21WAF1/CIP1 expression was not confirmed in this study.     

Expression of COX-2 is associated with accumulation of p53 in pancreatic cancer: analysis of COX-2 and p53 expression in premalignant and malignant ductal pancreatic lesions

OBJECTIVES: Cyclooxygenase-2 (COX-2) and tumor suppressor p53 are molecules that are linked to the oncogenesis of pancreatic cancer. COX-2 represents a key modulatory molecule in inflammation and carcinogenesis, and is known to be implicated in the positive regulation of growth and tumorigenesis. Abnormal expression of p53 is common in many human neoplasms including pancreatic cancer. Recent studies demonstrated functional interactions between p53 and COX-2. The p53-dependent upregulation of COX-2 was proposed to be another mechanism by which p53 could abate its own growth-inhibitory and apoptotic effects. METHODS: In this study, we immunohistochemically analyzed the expression of COX-2 and p53 in 95 pancreatic resection specimens [adenocarcinomas, 95 lesions; pancreatic intraepithelial neoplasias (PanINs), 155; normal ducts, 70]. RESULTS: The expression of COX-2 increased progressively with the grade of ductal lesions (P<0.00001). A statistically significant difference of COX-2 expression between normal ducts and low-grade PanINs was revealed (P=0.0042). COX-2 overexpression was demonstrated in 82 PanINs (52.9%), and in 76 adenocarcinomas (80%). No significant correlation between the grade of adenocarcinoma and COX-2 expression was revealed (P=0.2). The expression of p53 again increased progressively with the grade of lesions (P<0.00001) with a significant increase in high-grade PanINs. A correlation between COX-2 and p53 expression levels in carcinomas was revealed (P=0.0002), and an accumulation of p53 was associated with COX-2 overexpression in premalignant and malignant ductal lesions. CONCLUSION: These findings confirmed the generally accepted pancreatic cancer progression model, and supported the concept of the interactive role of COX-2 and p53 in pancreatic cancer carcinogenesis, which offers opportunities for targeted therapy and chemoprevention of pancreatic cancer using COX-2 inhibitors.     

Distribution of Intraductal Lesions in Small Invasive Ductal Carcinoma of the Pancreas

Aims: To investigate the distribution of intraductal lesions in small invasive ductal carcinoma (IDC) of the pancreas. Methods: In 21 cases with IDCs microscopically ≤20 mm in diameter, the intraductal lesions around a mass were studied histologically and mapped according to the pancreatic intraepithelial neoplasia (PanIN) classification. Results: PanIN-3, PanIN-2, PanIN-IB and PanIN-IA were found in 17, 10, 20 and 21 of 21 cases, respectively, and were divided into lesions in adjacent and distal areas, respectively defined as within and beyond 10 mm from the mass as follows: 100% (17/17), 100% (10/10), 95.0% (19/20) and 90.5% (19/21) in the former, while 23.5% (4/17), 50.0% (5/10), 90.0% (18/20) and 95.2% (20/21) in the latter. PanIN-3 lesions were predominantly found in the area adjacent to the mass. In some cases, significant PanIN-3 appeared to show a consecutive geographic extension around the mass via the main pancreatic duct (MPD). The distance of PanIN-3 spread was within 25 (mean 10.5) mm from the mass edge. PanIN-2 lesions were found in the area adjacent to the mass and discontinuous with the mass or PanIN-3 lesions. PanIN-IB and PanIN-IA tended mainly to exist sporadically throughout the entire pancreas. In the MPD, PanIN-3 was found in 14 (82.4%) of 17 cases and in 36 (32.1%) of 112 lesions, which was most frequent in intraductal lesions. Conclusions: PanIN-3 lesions might be an intraductal extension of the main tumor. The resection margin of 25 mm, at least longerthan 11 mm, from the mass edge will be necessary.