Zystische Pankreasl?sionen

Cystic changes of the pancreas comprise a large spectrum of neoplastic and non-neoplastic lesions. Among these are five entities, i.e. pseudocysts, intraductal papillary mucinous neoplasms (IPMN), mucinous cystic neoplasms (MCN), serous cystic neoplasms (SCN) and solid pseudopapillary neoplasms (SPN), which represent 95% of all cystic pancreatic lesions. While SCN and SPN have a good prognosis, IPMN and MCN have a high risk of malignancy as they are potential precursors of pancreatic ductal adenocarcinoma. The differential diagnosis between these five entities is based on epidemiology, pathology and clinical criteria. Consideration of these criteria allows in many cases a preoperative stratification that is the basis for an adequate therapy.     

Mucin expression profile in pancreatic cancer and the precursor lesions

In this review article, we demonstrate the mucin expression profile in normal tissue, invasive ductal carcinoma (IDC), two subtypes of intraductal papillary–mucinous neoplasm (IPMN dark cell type and IPMN clear cell type), pancreatic intraepithelial neoplasia (PanIN), and mucinous cystic neoplasm (MCN) of the pancreas. In MUC1, there are various glycoforms, such as poorly glycosylated MUC1, sialylated MUC1, and fully glycosylated MUC1. IDCs showed high expression of all the glycoforms of MUC1. IPMNs dark cell type showed no expression or low expression of all the glycoforms of MUC1. IPMNs clear cell type showed low expression of poorly glycosylated MUC1, but expression of sialylated MUC1 and fully glycosylated MUC1. Expression of MUC2 was negative in IDCs, high in IPMNs dark cell type and low in IPMNs clear cell type. MUC5AC was highly expressed in IDCs, IPMNs dark cell type, and IPMNs clear cell type. MUC6 expression was higher in IPMNs clear cell type than in IDCs and IPMNs dark cell type. Our recent study demonstrated that high expression of MUC4 in IDCs is correlated with a poor outcome for patients. In PanINs, expression of both MUC5AC and MUC6 are an early event, whereas up-regulation of MUC1 is a late event. MCNs do not look as if they will show a specific mucin expression profile according to the literature review.     

粘蛋白MUC1、MUC2、MUC4和MUC5AC在胰腺导管腺癌中的表达及意义

目的 研究胰腺导管腺癌(pancreatic ductal adenocarcinoma,PDA)组织中粘蛋白MUC1、MUC2、MUC4和MUC5AC的表达及其与临床病理参数间的关系.方法 应用SP免疫组织化学方法检测26例PDA、4例CP、16例正常胰腺组织、2例导管内乳头状黏液性肿瘤(IPMN)、4例实性假乳头状瘤(SPT)和1例浆液性囊性肿瘤(SCN)组织中MUC1、MUC2、MUC4、MUCSAC的表达.结果 正常胰腺和CP组织仅有MUC1表达,表达率均为100%;PDA中MUC1、MUC4和MUC5AC表达率分别为100%、88.5%(23/26)和76.9%(20/26);2例IPMN均见MUC2和MUC5AC表达;SPT和SCN中4种粘蛋白均无表达.MUC4和MUC5AC表达同PDA的临床病理参数之间无相关性(P＞0.05).结论 PDA时存在多种粘蛋白的表达,联合检测MUC1、MUC2、MUC4和MUC5AC的表达可能有助于对PDA的诊断和鉴别诊断.     

Precancerous lesions of the pancreas

Pancreatic cancer has a very poor prognosis, with a five year survival of only 5%. New studies have shown that it takes over 11 years for cells to develop invasive capability. This provides an opportunity to intervene if precursor lesions can be detected. This paper reviews the molecular, pathological, clinical findings and management of pancreatic intraepithelial neoplasia (PanIN), intraductal pancreatic mucinous neoplasm (IPMN) and mucinous cystic neoplasm (MCN), three precursor lesions which can give rise to invasive carcinoma of the pancreas.     

Resektion zystischer Pankreastumoren

Cystic tumors of the pancreas are diagnosed increasingly more due to increasing life expectancy and the moderate use of modern radiological diagnostics. Intraductal papillary mucinous neoplasms of the pancreas (IPMN), mucinous cystic neoplasms (MCN), solid pseudopapillary neoplasms (SPN) and serous cystic neoplasms (SCN) represent over 90?% of all cystic neoplasms of the pancreas. Although serous cystic lesions have a low or even no potential for malignant transformation, they are mostly resected when symptomatic. In contrast, mucinous lesions have an increased malignant potential and should therefore be resected in almost all cases. While this is true for all cases of MCNs and SPNs this is controversial for all IPMNs as they show a wide spectrum of morphological variants. The IPMNs may arise in the main pancreatic duct, major side branches or in both (mixed type). Although all IPMNs are considered to be precursor lesions to pancreatic adenocarcinomas it is not clear what the time course of such potential neoplastic transformation might be and whether all lesions progress to malignant tumors. As no currently used diagnostic test can reliably differentiate between benign and malignant tumors, the majority of newly diagnosed IPMNs should undergo surgical resection. According to current treatment guidelines (Sendai criteria), asymptomatic side branch IPMNs of less than 3 cm in diameter without suspicious radiological features, such as nodules, thickness of the cystic wall or size progression can be treated conservatively without the need for surgical resection. Recently, this approach has become controversial due to a relevant number of IPMNs reported as Sendai negative that showed malignant transformation on final histological examination.     

Unklare Gewichtsabnahme, Übelkeit und eine abdominelle Raumforderung

Mucinous cystic neoplasia (MCN) and the differential diagnosis of intraductal papillary mucinous neoplasia (IPMN) are common neoplasias of the pancreas with increasing prevalence. The latter often result in recurrent episodes of chronic pancreatitis. We report on an 89-year-old patient who was admitted from a home for the elderly to our hospital with nausea and shortness of breath. The advanced age, previous history of pancreatitis and mucinous secretion from the papillae were obvious symptoms of IPMN in this patient.     

International consensus guidelines for management of intraductal papillary mucinous neoplasms and mucinous cystic neoplasms of the pancreas.

Non-inflammatory cystic lesions of the pancreas are increasingly recognized. Two distinct entities have been defined, i.e., intraductal papillary mucinous neoplasm (IPMN) and mucinous cystic neoplasm (MCN). Ovarian-type stroma has been proposed as a requisite to distinguish MCN from IPMN. Some other distinct features to characterize IPMN and MCN have been identified, but there remain ambiguities between the two diseases. In view of the increasing frequency with which these neoplasms are being diagnosed worldwide, it would be helpful for physicians managing patients with cystic neoplasms of the pancreas to have guidelines for the diagnosis and treatment of IPMN and MCN. The proposed guidelines represent a consensus of the working group of the International Association of Pancreatology.     

Synchronous pancreatic solid pseudopapillary neoplasm and intraductal papillary mucinous neoplasm

Solid pseudopapillary neoplasm (SPN) is a rare and low-grade malignant pancreatic neoplasm composed of poorly cohesive monomorphic neoplastic cells forming solid and pseudopapillary structures with frequent hemorrhagic-cystic degeneration. Intraductal papillary mucinous neoplasm (IPMN) is a pancreatic exocrine tumor composed of intraductal papillary growth of mucin containing neoplastic cells in the main pancreatic duct or its major branches. In the case presented here, a 53-year-old, Japanese man was found to have multiple cystic lesions and dilatation of the main pancreatic duct in the neck of the pancreas. Histological examination revealed a main-duct and branch-duct type IPMN, of the gastric-type, involving the neck of the pancreas, associated with a 0.5 cm SPN in the caudal side of the IPMN. We diagnosed this case as synchronous SPN and IPMN. As far as we know, only one other case of synchronous SPN and IPMN has been reported. Both the present case and the previously reported case showed abnormal nuclear expression of β-catenin in SPN, whereas IPMN showed no abnormal nuclear expression. These results suggest that β-catenin abnormality is not a common pathogenetic factor of synchronous SPN and IPMN.     

Analysis of c-kit protein expression in pancreatic neoplasms and its implication for prognosis

BACKGROUND/AIMS: To evaluate the expression and role of c-kit protein in the neoplasia of pancreatic neoplasms and its relationship to prognosis in invasive ductal carcinoma (IDC) of the pancreas. METHODOLOGY: The immunohistochemical expression of c-kit protein was studied in normal pancreatic tissues, intraductal papillary-mucinous neoplasms of the pancreas (IPMN), mucinous cystic neoplasm of the pancreas (MCN), and IDC of the pancreas. The immunoreactive score (IRS) of c-kit protein expression was examined in normal pancreatic ductal cells, neoplastic cells, and pancreatic endocrine cells. RESULTS: The IRS values of c-kit protein expression in various neoplastic cells were significantly higher than those in normal ductal cells. No significant difference was seen between IRS values of c-kit protein expression in various pancreatic neoplastic cells of IDC of the pancreas, IPMN and MCN. No significant difference was seen between IRS values of c-kit expression in endocrine cells among various pancreatic tissues. Furthermore, a survival analysis in patients with IDC of the pancreas showed an obvious trend toward decreased survival in patients with c-kit-positive cancer, and c-kit protein expression did not correlate with any clinicopathological factors in IDC of the pancreas. CONCLUSIONS: c-kit protein expression may play an important role in neoplasia of pancreatic neoplasms. In view of the result that c-kit protein expression was found in 8% of IDC of the pancreas, a clinical trial for STI-571 (Glivec) against pancreatic cancer may be warranted for selected pancreatic cancer patients with c-kit protein expression.     

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.     

Accuracy and agreement of a large panel of endosonographers for endomicroscopy-guided virtual biopsy of pancreatic cystic lesions

BackgroundAlthough emerging data evidences that EUS-guided needle-based confocal laser endomicroscopy (nCLE) accurately diagnoses pancreatic cystic lesions (PCLs), there are a lack of interobserver agreement (IOA) studies utilizing reference histopathological diagnosis and for specific PCL subtypes. Hence, we sought to assess the IOA, intra-observer reliability (IOR), and diagnostic performance of EUS-nCLE using a large cohort of patients with histopathological diagnosis amongst a broad panel of international observers.MethodsEUS-nCLE videos (n = 76) of subjects with PCLs [intraductal papillary mucinous neoplasm (IPMN), mucinous cystic neoplasm (MCN), serous cystadenoma (SCA), pseudocyst, and cystic-neuroendocrine tumors/solid pseudopapillary neoplasm (cystic-NET/SPN)], simulating clinical prevalence rates were obtained from 3 prospective studies. An international panel of 13 endosonographers with nCLE experience, blinded to all PCL data, evaluated the video library twice with a two-week washout for PCL differentiation (mucinous vs. non-mucinous) and subtype diagnosis.ResultsThe IOA (κ = 0.82, 95% CI 0.77–0.87) and IOR (κ = 0.82, 95% CI 0.78–0.85) were “almost perfect” to differentiate mucinous vs. non-mucinous PCLs. For PCL subtype, IOA was highest for SCA (almost perfect; κ = 0.85), followed by IPMN (substantial, κ = 0.72), and cystic-NET/SPN (substantial, κ = 0.73). The IOA was moderate for MCN (κ = 0.47), and pseudocyst (κ = 0.57). Compared to histopathology, observers differentiated mucinous vs. non-mucinous PCLs with high accuracy (94.8%, 95% CI 93.3–96.1). For detecting specific PCLs subtypes, EUS-nCLE was highly accurate in diagnosing non-mucinous cysts (SCA: 98%; cystic-NET/SPN: 96%; pseudocyst: 96%) and slightly less accurate for mucinous lesions (IPMN: 86%; MCN: 84%).ConclusionDiagnosis of PCLs by EUS-nCLE guided virtual biopsy is very accurate and reliable for the most prevalent pancreatic cysts in clinical practice.     

Mucinous cystic neoplasms of the pancreas: pathology and molecular genetics

Mucinous cystic neoplasm (MCN) of the pancreas is a distinct clinicopathological entity characterized by mucin-producing epithelial and cyst-forming neoplasm with “ovarian-type” stroma beneath the epithelial component. It is clearly distinguished from ductal adenocarcinoma and intraductal papillary mucinous neoplasm (IPMN). However, MCN can progress to infiltrating carcinoma, and frequently shows a similar histological pattern to ductal adenocarcinoma. Several genetic alterations such as K-ras oncogene mutation, and epigenetic alterations such as hypermethylation of p16 in the invasive component of MCN are also common with ductal adenocarcinoma. Furthermore, recent technologies, including a laser-assisted microdissection system for histological slides and global gene expression profilings using DNA microarrays, made possible to identify more information about molecular abnormalities of MCNs. It is important to diagnose the lesions before they progress to an invasive carcinoma. MCN is one of the precursors of invasive pancreatic carcinoma.     

Pancreatic mucinous cystic neoplasm defined by ovarian stroma: demographics, clinical features, and prevalence of cancer.

BACKGROUND & AIMS: Pancreatic mucin-producing cystic neoplasms are classified into 2 distinct entities: mucinous cystic neoplasm (MCN) and intraductal papillary mucinous neoplasm (IPMN). In previous studies, MCN often has been defined loosely and has not always been distinguished clearly from IPMN. Our aims were to determine the demographics, clinical features, and prevalence of invasive cancer in MCN defined by the presence of characteristic ovarian stroma. METHODS: By using the presence of ovarian stroma as a requisite criterion for diagnosis of MCN, a single pathologist, unaware of clinical information, identified 56 MCNs from 243 mucin-producing neoplasms resected at Mayo Clinic between 1986 and 2003. Medical records of the MCN patients were reviewed to obtain clinical and demographic data. RESULTS: Patients with MCN were almost exclusively (98%) women; we identified 1 man with a neoplasm containing ovarian stroma. The mean (+/-SD) age at resection was 48 +/- 15 years (84% < 60 y). Abdominal pain was the most common presenting symptom; 16% were asymptomatic. Most MCN (93%) were in the pancreatic body/tail region. Their median size was 5 cm (61% > or =5 cm). Histologically, 50 (89%) were adenomas, 2 (4%) had carcinoma-in-situ, and 4 (7%) had invasive cancer. None of the 22 MCNs <5 cm in size had invasive cancer. No patient with noninvasive disease had a recurrence after resection. CONCLUSIONS: MCN defined by ovarian stroma has a distinct demographic and clinical profile and a low prevalence of invasive cancer. These observations suggest that ovarian stroma should be used as the defining criterion for diagnosing MCN.     

Clinicopathologic review of 41 cases of pancreatic mucinous cystic neoplasms]

BACKGROUND/AIMS: Intraductal papillary mucinous neoplasms (IPMN) and mucinous cystic neoplasms are included in mucin-producing pancreatic tumors. The reports about IPMN are not uncommon but those about the mucinous cystic neoplasms are relatively few. The aims of this study were to define the natural history of resected mucinous cystic neoplasms of the pancreas and to identify the findings which suggest malignancy. METHODS: The authors retrospectively evaluated the clinical outcomes of 41 patients with mucinous cystic neoplasms who were surgically resected at Asan Medical Center between 1995 and 2004. RESULTS: Women (n=33) were more frequently affected than men (n=8). Thirty three patients (80.6%) had adenoma, 1 (2.4%) borderline malignancy, 1 (2.4%) carcinoma in situ, and 6 (14.6%) invasive mucinous cystadenocarcinoma. The most frequent symptom was abdominal pain (39%). About half of the enrolled patients were asymptomatic. Unilocular type (79%) was more frequent than the multilocular type (21%) on gross morphology. The tumor size of invasive mucinous cystic neopolasms was larger than that of non-invasive mucinous cystic neoplalsms (p=0.01). Abdominal pain was more frequent in invasive mucinous cystic neoplasms (p=0.026). On gross morphology, mural nodules were detected in 4 of 6 patients with invasive mucinous cystic neoplasms. However, they were not detected in any patients with non-invasive mucinous cystic neoplasms. Recurrence developed in none of the 35 patients with non-invasive mucinous cystic neoplasms, however 2 of the 6 patients with invasive mucinous cystic neoplasms died within 5 years. CONCLUSIONS: Clinical predictors of invasive mucinous cystic neoplasms are suggested to be tumor size and abdominal pain. The prognosis of the non-invasive mucinous cystic neoplasms is excellent when curative resection is performed.     

胰腺囊性病变的临床特征和诊治分析

背景:随着影像学技术的进步,胰腺囊性病变的检出率逐年升高,但鉴别不同类型的胰腺囊性病变仍是临床的棘手问题。目的:分析胰腺囊性病变的临床特征和诊治方法。方法:纳入2003年1月~2013年1月上海交通大学附属第一人民医院收治的胰腺囊性病变患者,对入组患者的临床表现、实验室检查、影像学特征以及治疗方法进行回顾性分析。结果:共49例患者纳入研究,其中假性囊肿13例、潴留囊肿4例、先天性囊肿2例、浆液性囊性肿瘤(SCN)9例、黏液性囊性肿瘤(MCN)11例、导管内乳头状黏液性肿瘤(IPMN)7例、实性-假乳头状肿瘤(SPN)3例。49例患者中16例患者无症状,其余33例患者表现为腹痛、腹胀、恶心、呕吐、发热等。13例胰腺假性囊肿患者均有急、慢性胰腺炎或外伤病史,3例IPMN患者血清CA19-9升高。B超、CT、MRI/MRCP、EUS诊断胰腺囊性病变的准确率分别为24.5%、32.7%、61.1%、100%。49例患者均接受手术治疗,分别行内引流术、囊肿切除术、胰十二指肠切除术、胰体(尾)切除术以及节段性胰腺切除术。结论:胰腺囊性病变无特异性临床表现。CT、MRI/MRCP作为无创检查手段,应广泛用于囊性病变的诊断和评估,EUS可作为进一步检查手段。选择合理的手术方案是治疗胰腺囊性病变的关键。     

Mucinous cystic neoplasm of the pancreas associated with pregnancy: report of two cases

Pancreatic neoplasms during pregnancy are rare. We describe two cases of mucinous cystic neoplasm (MCN) associated with pregnancy. A 34-year-old woman in the 26th week of pregnancy was given a diagnosis of MCN measuring 19 cm in diameter. We decided to resect it post partum in consideration of the risk of abortion. She had a healthy infant in the 40th week of pregnancy and three months later, distal pancreatectomy was performed. Pathological analysis revealed a mucinous cystadenoma of the pancreas. The second case was a 36-year-old woman. She was given a diagnosis of MCN, measuring 16 cm in diameter, post partum and distal pancreatectomy was performed. Pathologically, the tumor was an invasive mucinous cystadenocarcinoma of the pancreas. In this report, we did an extensive literature review and discussed the management of MCN during pregnancy with special reference to the timing of the operation and the relationship between tumor growth and sex hormones.     

Pancreatic ductal adenocarcinomas with multiple large cystic structures: A clinicopathologic and immunohistochemical study of seven cases

Background/objectivesPancreatic ductal adenocarcinoma (PDA) with cystic change is classified into several types according to the features of the cysts; however, those tumors do not constitute a uniform group, and the classification is controversial. In this study, we have described a series of cystic PDAs that show distinctive and previously unreported morphologic and immunohistochemical features.MethodsWe analyzed 200 cases of PDA treated surgically at a single institution, and extracted the clinical and histopathological features of 7 tumors showing multiple large cystic (MLC) structure.ResultsPreoperative radiographic images revealed a multilocular mass in the pancreas which was similar to intraductal papillary mucinous neoplasm or mucinous cystic neoplasm. These tumors were associated with more than 5 large cystic structures and numerous intratumoral microcysts lined by epithelial cells with various degrees of atypia. The average maximal diameter of the cysts (3.7 cm) was much larger than that of previously reported. Immunohistochemically, the cyst-lining epithelia were almost negative for mucin core protein (MUC) 1, MUC2, and MUC6, and showed only focal staining for MUC5AC. Maspin, CEA, and p53 were strongly positive, and the Ki-67 labeling index was high in both cells in solid areas and cyst-lining epithelia.ConclusionWe considered the MLC structures in PDA to be a mixture of ectatic neoplastic glands and retention cysts with ductal cancerization or pancreatic intraepithelial neoplasia (PanIN); however, they might represent a new entity of cystic PDA because of the unusually large size of the dilated cysts.     

Definition of MCN (mucinous cystic neoplasm of the pancreas) and a proposal for a new concept of MRN or MSN (mucinous round or spherical neoplasm)

The differential diagnosis of IPMN and MCN is very important for clinicians. MCN is reported to develop in middle-aged females (mean age 48 years) and in the body and tail of the pancreas. Some doctors insist that ovarian-like stroma is absolutely necessary for the definition of MCN. Prompt resection of MCN after diagnosis is desirable. In contrast, about 60% of cases with branch-type IPMN do not require an operation. Therefore, one of the important goals in the differential diagnosis of MCN and branch-type IPMN is to determine the surgical indications before the operation. We believe that MCN and IPMN should be defined by imaging procedures before the operation. We suggest that a neoplasm with an appearance similar to an orange should be diagnosed as MCN, while that with an appearance similar to a bunch of grapes in MRCP should be diagnosed as branch-type IPMN. Proposal of a new concept: If the term MCN is restricted to neoplasms that exhibit ovarian-like stroma, we propose that lesions which are surrounded by a very thick capsule, and which show an orange-like appearance by imaging procedures without histological ovarian-like stroma should be called MRN (mucinous round neoplasm) or MSN (mucinous spherical neoplasm).     

Clinicopathological and prognostic significance of MUC13 and AGR2 expression in intraductal papillary mucinous neoplasms of the pancreas

Background

Intraductal papillary mucinous neoplasm (IPMN) of the pancreas is a primary pancreatic ductal epithelial neoplasm with the potential to develop into an invasive adenocarcinoma. This study aimed to investigate the clinicopathologic and prognostic significance of four potential biomarkers for the preoperative evaluation of patients with 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.