Expression of mucin core proteins, trefoil factors, APC and p21 in subsets of colorectal polyps and cancers suggests a distinct pathway of pathogenesis of mucinous carcinoma of the colorectum

Mucin core proteins are expressed in a tissue and cell type specific manner in the normal gastrointestinal tract. Aberrant expression of mucin core proteins have been reported in colorectal neoplasms. To examine the relationship between subsets of colorectal polyps and non-mucinous and mucinous adenocarcinomas of the colorectum, we evaluated the frequency of the expression of cell lineage associated mucin core proteins (MUC5AC and MUC2), trefoil factors (TFF1 and TFF3), and APC and p21 in these tissues. An immunohistochemical study was performed in 10 normal rectal mucosa samples (NM) 21 hyperplastic polyps (HP), 20 serrated adenomas (SA), 25 tubular adenomas (TA), 13 tubulovillous adenomas (TVA), 7 villous adenomas (VA), 42 non-mucinous colorectal cancers (NMC), and 19 mucinous colorectal cancers (MC). A higher frequency of ectopic expression of gastric foveolar mucin, MUC5AC, and the expression of intestinal goblet cell mucins, MUC2, was observed respectively in HP (100%, 100%), SA (85%, 85%), TVA (85%, 85%), and VA (100%, 100%), compared to TA (32%, p<0.002; 36%, p<0.01). MC (68%, 100%) also showed a higher frequency of the expression of MUC5AC and MUC2 compared to NMC (31%, p=0.001; 38%, p<0.001), and TFF1 showed similar patterns of expression. APC protein and p21 were also expressed at a higher frequency in HP (100%, 100%), and SA (67%, 83%), than in TA (29%, p<0.03; 46%, p<0.05). MC (68%, 100%) showed a higher frequency of expression of APC protein and p21 than NMC (19%, p<0.001; 45%, p<0.01). Our results showed that MUC2 expression and de novo ectopic expression of MUC5AC and TFF1 are more frequent in HP, SA, TVA, VA, and MC than in TA and NMC. These results suggest that simultaneous activation of differentiation pathways of goblet cells and gastric foveolar cells may occur predominantly in the pathogenesis of HP, SA, TVA, VA, and MC, while the pathogenesis of TA and NMC are less likely to involve these processes.     

Mucin core protein expression in colorectal cancers with high levels of microsatellite instability indicates a novel pathway of morphogenesis.

Particular mucinous phenotypes have been associated with serrated epithelial polyps of the colon. These polyps also show a high frequency of DNA instability. The aim of this study was to examine the expression of mucins in colorectal cancers that arise through the suppressor and mutator pathways. The immunohistochemical distribution of the human apomucins MUC1, MUC2, MUC4, and MUC5AC was determined in 93 sporadic colorectal cancers classified previously (J. R. Jass et al., J. Clin. Pathol., 52: 455-460, 1999) according to levels of DNA microsatellite instability (MSI) as 22 MSI-high (MSI-H), 24 MSI-low (MSI-L), and 47 MS stable (MSS). MUC2 expression was observed in 19 (86%) MSI-H, 10 (42%) MSI-L, and 15 (32%) MSS cancers (P = 0.0001); and MUC5AC expression was observed in 17 (77%) MSI-H, 8 (33%) MSI-L, and 13 (28%) MSS cancers (P = 0.0003). There was no association between MUC1 or MUC4 expression and MSI status. The mucinous phenotype described in serrated polyps (MUC2+/MUC5AC+) was seen in 15 (68%) of 22 MSI-H and only 10 (14%) of 71 MSI-L/MSS cancers (P < 0.0001). Increased expression of the secretory mucins MUC2 and MUC5AC was observed in sporadic MSI-H cancers. Identical mucin changes and DNA MSI occurred in serrated polyps of the colorectum, which suggests that these lesions may represent precursors of MSI-H cancers.     

Immunohistochemical study of MUC5AC expression in human gastric carcinomas using a novel monoclonal antibody

In order to investigate the expression of MUC5AC mucin in normal gastric mucosa and gastric carcinomas, we produced 3 monoclonal antibodies (MAbs) using a MUC5AC synthetic peptide. The immunohistochemical study was performed using one of these MAbs (CLH2) which reacted with the different designs of peptides based on the MUC5AC tandem repeat and with native and deglycosylated mucin extracted from gastric tissues. CLH2 immunoreactivity was restricted to foveolar and mucopeptic neck cells in normal gastric mucosa. No reactivity was observed in type-1 intestinal metaplasia. Out of 66 gastric carcinomas, 42 (63.6%) expressed MUC5AC. Most diffuse carcinomas were positive (83.3%), whereas only 59.3% of intestinal and 40.0% of atypical carcinomas expressed MUC5AC (p < 0.05). Gastric carcinomas with mixed pattern showed immunoreactivity in diffuse areas and decreased immunoreactivity in intestinal areas. Every early gastric carcinoma expressed MUC5AC, in contrast to 58.6% of advanced carcinomas (p < 0.05). A trend toward decreased immunoreactivity was observed in deep areas of advanced carcinomas in comparison with the respective superficial areas. Taking together the specific staining of foveolar and mucopeptic neck cells and the absence of immunoreactivity in intestinal metaplasia, we conclude that MUC5AC expression may be used as a marker of gastric differentiation. This assumption is further supported by the finding of MUC5AC immunoreactivity in most diffuse carcinomas, which usually display morphologic and histochemical signs of gastric differentiation. The expression of MUC5AC in early gastric carcinomas, regardless of their histologic type, suggests that all gastric carcinomas retain at least some cells with a gastric phenotype during the first steps of neoplastic development. Int. J. Cancer 74:112–121. © 1997 Wiley-Liss, Inc.     

Aberrant expression of MUC5AC and MUC6 gastric mucin genes in colorectal polyps

Altered mucin glycosylation and the de novo appearance of gastric mucin antigens have been described in colonic adenomas. The purpose of our study was to determine if expression of the gastric mucin genes MUC5AC and MUC6 occurs in colorectal adenomas and whether this correlates with histopathologic criteria of malignant potential. Immunohistochemical staining using antibodies against MUC5AC and MUC6 tandem repeat synthetic peptides was performed on specimens of normal colon mucosa (n = 26), hyperplastic polyps (n = 9) and adenomatous polyps (n = 111). Mucin mRNA levels were determined using RNase protection assays using riboprobes corresponding to unique non‐repetitive sequences. MUC5AC and MUC6 staining were rarely detected and of low intensity in normal colon and hyperplastic polyps. The number of immunoreactive polyps and intensity of MUC5AC and MUC6 staining were greatest in larger adenomas of moderate villous histology and dysplasia. MUC5AC and MUC6 staining tended to decrease in highly villous polyps with severe dysplasia. Increased MUC5AC mRNA levels were found in 26/45 of adenomas tested compared with 0/9 normal colon specimens. MUC6 mRNA levels were found in 20/45 of adenomas compared with 1/9 normal colon specimens. MUC5AC and MUC6 mRNA were present more frequently and at higher levels in polyps with intermediate stages of size, villous histology and dysplasia. We conclude that aberrant expression of MUC5AC and MUC6 mucin genes is likely responsible for an expanded repertoire of mucin antigen expression in colorectal neoplasia. Int. J. Cancer 80:210–218, 1999. Published 1999 Wiley‐Liss, Inc.     

MUC1, MUC2, MUC5AC, and MUC6 expressions in gastric carcinomas: their roles as prognostic indicators.

BACKGROUND: Although mucin expressions appear to be correlated with prognoses in patients with various cancers, several studies have reported conflicting and inconclusive results on the prognostic significance of mucin expression in gastric carcinomas. METHODS: To clarify the correlations between clinicopathologic profiles and the patients' survival, the expression of MUC1, MUC2, MUC5AC, MUC6 mucins and the p53 protein were evaluated immunohistochemically in 300 consecutive gastric carcinomas using the tissue-array method. In addition, 59 gastric adenomas and 57 adenoma-associated carcinomas were investigated. RESULTS: MUC1 was expressed in 2 (3.4%) cases of gastric adenoma, and MUC2 in 19 (32.2%) cases of gastric adenoma, out of a total of 59 lesions. In consecutive gastric carcinomas, 24.3% of gastric carcinomas expressed MUC1, 27.3% expressed MUC2, 38.0% expressed MUC5AC and 12.7% expressed MUC6. The rate of MUC1 expression in gastric carcinomas was significantly higher than in associated gastric adenomas (P < 0.01). The patients with MUC1-positive carcinomas showed significantly poorer survival than those with MUC1-negative carcinomas. On the other hand, MUC2, MUC5AC and MUC6 expressions were not significantly associated with patient survival. Interestingly, combined evaluation revealed that the group with the MUC1-negative plus p53-negative expression pattern showed a better prognosis than the remaining cases. In contrast, the group with the MUC2-negative plus p53-positive pattern showed a worse prognosis. CONCLUSIONS: Mucin expression is altered in gastric adenoma and carcinoma, and MUC1 mucin expression is significantly associated with poorer outcome in gastric carcinomas. A MUC1-negative plus p53-negative pattern or a MUC2-negative plus p53-positive pattern may predict outcome in patients with gastric carcinomas.     

The serrated neoplasia pathway of colorectal tumors: Identification of MUC5AC hypomethylation as an early marker of polyps with malignant potential

The serrated neoplasia pathway accounts for 20–30% of colorectal cancers (CRC), which are characterized by extensive methylation (CpG island methylation phenotype, CIMP), frequent BRAF mutation and high microsatellite instability (MSI). We recently identified MUC5AC mucin gene hypomethylation as a specific marker of MSI CRC. The early identification of preneoplastic lesions among serrated polyps is currently challenging. Here, we performed a detailed pathological and molecular analysis of a large series of colorectal serrated polyps and evaluated the usefulness of mucin genes MUC2 and MUC5AC to differentiate serrated polyps and to identify lesions with malignant potential. A series of 330 colorectal polyps including 218 serrated polyps [42 goblet cell‐rich hyperplastic polyps (GCHP), 68 microvesicular hyperplastic polyps (MVHP), 100 sessile serrated adenoma (SSA) and eight traditional serrated adenoma (TSA)] and 112 conventional adenomas was analyzed for BRAF/KRAS mutations, MSI, CIMP, MLH1 and MGMT methylation, and MUC2 and MUC5AC expression and methylation. We show that MUC5AC hypomethylation is an early event in the serrated neoplasia pathway, and specifically detects MVHP and SSA, arguing for a filiation between MVHP, SSA and CIMP‐H/MSI CRC, whereas GCHP and TSA arise from a distinct pathway. Moreover, MUC5AC hypomethylation specifically identified serrated lesions with BRAF mutation, CIMP‐H or MSI, suggesting that it may be useful to identify serrated neoplasia pathway‐related precursor lesions. Our data suggest that MVHP should be recognized among HP and require particular attention.     

Expression of gastric mucin MUC5AC and gastric transcription factor SOX2 in ampulla of vater adenocarcinoma: comparison between expression patterns and histologic subtypes

The purpose of this study was to examine the expression pattern of MUC5AC and SOX2 in ampulla of vater adenocarcinoma and evaluate the association between expression of these gastric epithelial markers and the histologic phenotype of ampulla of vater carcinoma. Six surgically resected samples of ampulla of vater adenocarcinoma, including four intestinal type carcinomas and two pancreatobiliary type carcinomas, were studied. We performed immunohistochemistry with a monoclonal antibody against MUC5AC and a polyclonal anti-SOX2 antibody. In two of the four intestinal type carcinomas, MUC5AC and SOX2 were focally expressed in the superficial neoplastic mucosa. However, in the centre of the tumour and in other invasive lesions, including vascular invasive lesions and metastatic lymph nodes, neither MUC5AC nor SOX2 was expressed. In contrast, in both pancreatobiliary type carcinomas, expression of MUC5AC and SOX2 was maintained or increased in invasive lesions. Our immunohistochemistry data suggest that MUC5AC and SOX2 are associated with the pancreatobiliary phenotype of ampulla of vater carcinoma and involved in later events in carcinogenesis, such as invasion and metastasis.     

Regulation of the intestinal mucin MUC2 gene expression in vivo: evidence for the role of promoter methylation

In the present work we investigated the in vivo regulation of the mucin gene MUC2, which is overexpressed in all mucinous colorectal carcinomas. The inhibition of methylation by 5-azadeoxycytidine induces de novo expression of MUC2 in the colon carcinoma cell line COLO 205. The expression is retained in xenograft tissue and the cells give rise to MUC2-expressing tumours in nude mice. The strong expression of MUC2 in the normal human goblet cells and in the tissue of human mucinous colorectal carcinomas is associated with the average methylation of about 50% at every investigated CpG site of the MUC2 promoter. In contrast, MUC2 promoter in the non-expressing normal columnar cells and in the non-mucinous carcinoma tissue is methylated to nearly 100%. These data show that (i) low methylation of MUC2 promoter is associated with MUC2 expression in vivo and (ii) the pattern of MUC2 promoter methylation in the normal goblet or columnar cells most closely resembles that in mucinous or non-mucinous colorectal carcinomas, respectively. They indicate that MUC2 expression in vivo is regulated by promoter methylation and support the hypothesis that cells with goblet-like differentiation give rise to mucinous colonic carcinomas.     

Mucins and mucin binding proteins in colorectal cancer

Mucins are high-molecular weight epithelial glycoproteins with a high content of clustered oligosaccharides O-glycosidically linked to tandem repeat peptides rich in threonine, serine, and proline. There are two structurally and functionally distinct classes of mucins: secreted gel-forming mucins (MUC2, MUC5AC, MUC5B, and MUC6) and transmembrane mucins (MUC1, MUC3A, MUC3B, MUC4, MUC12, MUC17), although the products of some MUC genes do not fit well into either class (MUC7, MUC8, MUC9, MUC13, MUC15, MUC16).MUC1 mucin, as detected immunologically, is increased in expression in colon cancers, which correlates with a worse prognosis. Expression of MUC2 secreted gel-forming mucin is generally decreased in colorectal adenocarcinoma, but preserved in mucinous carcinomas, a distinct subtype of colon cancer associated with microsatellite instability. Another secreted gel-forming mucin, MUC5AC, a product of normal gastric mucosa, is absent from normal colon, but frequently present in colorectal adenomas and colon cancers.The O-glycosidically linked oligosaccharides of mucins can be described in terms of core type, backbone type, and peripheral structures. Colon cancer mucins have differences in both core carbohydrates and in peripheral carbohydrate structures that are being investigated as diagnostic and prognostic markers, and also as targets for cancer vaccines. Colon cancer mucins typically have increases in three core structures: Tn antigen (GalNAcThr/Ser), TF antigen (Gal3GalNAc) and sialyl Tn (NeuAc6GalNAc). The type 3 core (GlcNAc3GalNAc) predominant in normal colonic mucin is lacking in colon cancer mucins. There are cancer-associated alterations in the peripheral carbohydrates of colonic mucins including a decrease in O-acetyl-sialic acid and a decrease in sulfation. There are, however, cancer-associated increases in sialyl LeX and related structures on mucins and other glycoproteins that can serve as ligands for selectins, increasing the metastatic capacity of colon cancer cells. The endogenous galactoside-binding protein galectin-3, which is expressed at higher levels in colon cancers than normal colon, binds to colon cancer mucin as well as other glycoproteins. Interference of the binding of selectins and galectin-3 to mucin may show therapeutic or preventative promise for colon cancer.     

Abnormal expression of gastric mucin in human and rat aberrant crypt foci during colon carcinogenesis.

Colorectal cancer is a major cause of death in Europe and the USA, and much effort is therefore devoted to improve its early detection. In this article, we report the abnormal expression of gastric mucin in aberrant crypt foci (ACF) that appear in the colon mucosae removed from colorectal cancer patients and rats treated with methyl-N'-nitro-N-nitroso-guanidine (MNNG). We performed the immunoperoxidase test using monoclonal antibodies raised against gastric M1 mucin encoded by the MUC5AC gene and against rat gastric mucins (MAb 660), respectively. In both human and rat colon, these anti-gastric mucin MAbs stained specifically goblet cells within ACF. In humans, the M1/MUC5AC mucin was expressed in the upper part of the glands in hyperplastic ACF and in the typical ACF. In addition, the anti-gastric mucin MAbs stained some rare, scattered, histologically normal glands in the human and rat colon mucosae. These glands may be regarded as precursors of ACF. The abnormal expression of the MUC5AC gene constitutes a novel change in addition to genetic modifications already observed in ACF, and supports our previous findings demonstrating the potential of this gastric mucin as an early marker of human and rat colon carcinogenesis.     

Requirement of both mucins and proteoglycans in cell-cell dissociation and invasiveness of colon carcinoma HT-29 cells

Human colon carcinomas are characterized by an aberrant expression of mucins, which in some case leads to an abundant presence of mucus such as in mucinous and signet ring cell carcinomas. Cellular cloning of the human colon carcinoma cell line HT-29 (HT-29 STD), which is mainly composed of undifferentiated cells, yielded a highly mucin-secreting variant (HT-29 5M21). The latter cloned cells cultured on plastic display a polarized organization with an apical secretion of MUC5AC mucin (Lesuffleur et al., Int J Cancer 1998;76:383-92.). Our aim was to study these 2 cell-types as for the invasive and adhesive properties with regard to the function of E-cadherin. HT-29 STD cells were noninvasive in collagen type I, whereas HT-29 5M21 cells were invasive, and the latter behavior was connected to a loss of function of E-cadherin. Likewise, HT-29 5M21 cells were characterized by a cell-cell adhesion independent of E-cadherin, in contrast to the E-cadherin dependent cell-cell adhesion of HT-29 STD cells. Immunofluorescence of HT-29 5M21 cells cultured on collagen type I showed the disappearance of the polarized organization, with a redistribution of apical mucins to the entire cell surface. Treatment of HT-29 5M21 cells by 1-benzyl-2-acetamido-2-deoxy-alpha-D-galactopyranoside (GalNAcalpha-O-bn) or by beta-D-xyloside revealed that both mucins and proteoglycans were involved in the loss of E-cadherin function. The use of specific antibodies allowed to show that MUC5AC, MUC1 and heparan sulfate proteoglycans cooperated in the formation of a biological inhibitory complex towards the function of E-cadherin in this invasive HT-29 clone.     

Mucin expression in mucinous carcinoma and other invasive carcinomas of the breast.

To investigate mucin expression in breast cancer, immunohistochemical staining was performed on 30 mucinous carcinomas and 95 non-mucinous invasive carcinomas. MUC2 expression was detected in all mucinous carcinomas, but only in 11.1% of invasive ductal carcinomas, and in none of the invasive lobular carcinomas and medullary carcinomas. MUC1 is often expressed in invasive breast carcinoma, but not in medullary carcinoma. Strong cytoplasmic staining was seen in invasive ductal carcinoma, in contrast to surface membrane staining in mucinous carcinoma and intracytoplasmic vacuole staining in invasive lobular carcinoma. CA19-9 and CA50 expression in more than 25% of tumor cells was seen in 17.2 and 16.0% of invasive ductal carcinomas, respectively, but not in mucinous carcinomas. CA125 and human gastric mucin were rarely expressed in breast cancer, irrespective of histologic type.     

Mucins in neoplastic spectrum of colorectal polyps: can they provide predictions?

Background  

The significance of expression of different mucins in succession of malignant transformation of colorectal polyps is not determined yet. The aim of the present study was to determine the pattern of expression of MUC1, MUC2, MUC5AC and MUC6 in colorectal polyps and to evaluate the applicability of using mucin expression in predicting the extent of malignant transformation in colorectal polyps.     

三种粘蛋白在胃癌组织中表达及其临床意义

目的 研究粘蛋白（MUC1，MUC2，MUC5AC）在胃癌组织中表达及它们与临床病理学行为之间的关系。方法 应用免疫组化S－P法检测94例原发性的胃癌组织标本中MUC1，MUC2，MUC5AC在胃癌组织中的表达。结果 1.MUC1的阳性表达率为82％，不同组织学之间的表达有明显差异（P＜0.05)，在中高分化管状腺癌中表达最强，表达程度与病人年龄、淋巴结有无转移及肿瘤大小密切相关（P＜0.05)；2.MUC2表达的阳性率为84%，不同组织学类型肿瘤组织中的表达有显著性差异（P＜0.05)，在粘液腺癌中表达最强100％（7／7）；3.MUC5的阳性率为40％（38／94）,除性别之间存在差异外，与其它的临床资料无关。4.相关分析发现MUC1的表达与MUC2的表达呈正相关。结论 1、MUC1在不同的组织学类型的胃癌中表达不同，在中高分化腺癌中最高，并与淋巴结转移、肿瘤大小有关；2.MUC2在不同的组织学类型的胃癌中表达不同，粘液腺癌中表达最强，可作为研究粘液腺癌的较好指标；3.MUC5AC在胃癌组织中的表达下降，可作为研究胃癌发生、进展的较好指标。4.MUC1和MUC2之间可能有协同作用。     

Expression of MUC1 and MUC2 mucin gene products in human ovarian carcinomas

BACKGROUND: Aberrations in expression of mucin glycoproteins have been observed during malignant transformation of human ovarian epithelium. To date, several secretory mucin genes designated the MUC gene family have been identified, of which MUC1 encodes a mammary-type and MUC2 an intestinal-type epithelial mucin. However, information on the expression and potential value of MUC1 and MUC2 mucins in ovarian cancer is limited. METHODS: This study investigated immunohistochemical expressions of MUC1 and MUC2 mucins in 23 benign and 45 malignant human ovarian tumors to assess their clinicopathological relevance. RESULTS: All benign serous tumors and also associated normal-appearing epithelia expressed MUC1 mucin on the cell surfaces. Benign mucinous tumors occasionally expressed MUC1 and MUC2 mucins. Most serous carcinomas (19/21; 90%) expressed MUC1 but not MUC2 mucin. Of the 16 mucinous carcinomas, 10 (62%) and five (31%) expressed MUC1 and MUC2 mucins, respectively. Four of the five clear cell and the three endometroid type carcinomas expressed MUC-1 but not MUC-2 mucin. A significant association was found between a high expression of MUC1 and histological grade (P = 0.005) and also disease stage (P = 0.001). CONCLUSION: These results suggest that a high expression of MUC1 may contribute to a poor prognosis in ovarian carcinoma.     

Expression of Tn, sialosyl-Tn, and T antigens in human colon cancer

Mucin glycoproteins are major secretory products of the colon and contain O-linked oligosaccharides synthesized on a polypeptide backbone. The initial step in the synthesis of O-linked oligosaccharides is the addition of N-acetylgalactosamine to serine or threonine residues forming the Tn antigen. This substance can then receive additional carbohydrate residues such as sialic acid to form sialosyl-Tn antigen, or galactose to form T antigen. In the colon, the T antigen is an oncodevelopmental cancer-associated antigen but little is known about Tn and sialosyl-Tn expression. The present comparative immunohistochemical study was performed to analyze the expression of these antigens in fetal, normal adult, and malignant colorectal tissues with an aim toward elucidating whether Tn and sialosyl-Tn are also oncodevelopmental colon cancer-associated antigens and to gain insight into the earliest steps of mucin glycosylation in colonocytes. We used three reagents to detect Tn antigen (two monoclonal antibodies ETn1.01 and CU-1, and one lectin Vicia villosa), two reagents to detect sialosyl-Tn (monoclonal antibodies TKH2 and B72.3) and one to detect T antigen (monoclonal antibody AH9-16). Except for occasional reactivity with VVA and CU-1, cells of normal colonic mucosa did not express Tn, sialosyl-Tn, or T antigens. However, in the transitional mucosa immediately adjacent to cancer, all three antigens were expressed (ranging from 35 to 67% of cases depending upon the reagent). In colon cancers, the percentage of cases expressing each antigen were as follows: Tn 72-81%, sialosyl-Tn 93-96%, and T 71%. Unlike T antigen, which was preferentially expressed by moderately well- and well-differentiated adenocarcinomas, both Tn and sialosyl-Tn antigens were expressed by most histological subsets of colon cancers, including poorly differentiated adenocarcinomas and mucinous (colloid and signet ring cell type) carcinomas. The majority of cancers expressed both Tn and sialosyl-Tn, usually in association with T antigen. Only one cancer lacked all three antigens. Fetal colonic mucosal cells expressed all three antigens, particularly in goblet cell mucin. These results indicate that like T antigen, Tn and sialosyl-Tn are oncodevelopmental cancer-associated antigens in the colon. Moreover, Tn and sialosyl-Tn antigens appear to be useful markers of poorly differentiated adenocarcinomas and mucinous carcinomas: two histological subsets that often fail to express other cancer-associated antigens and that are often associated with a poor clinical outcome.(ABSTRACT TRUNCATED AT 400 WORDS)     

Diagnostic utility of mucin profile in fine-needle aspiration specimens of the pancreas: an immunohistochemical study with surgical pathology correlation

BACKGROUND: The cytologic differentiation between neoplastic and reactive/reparative processes in the endoscopic ultrasound-guided fine-needle aspirations (EUS-FNA) of the pancreas can be difficult. Malignant transformation of the pancreatic ductal epithelium changes the expression of apomucins. The goal of the current study was to determine an optimal immunohistochemical panel of mucin (MUC) antibodies that would allow the cytomorphologic distinction of pancreatic ductal adenocarcinoma and its differentiation from reactive/reparative processes and inadvertently sampled gastric and duodenal mucosa. METHODS: Pancreatic EUS-FNA specimens performed on 351 patients were reviewed. Expression profiles of MUC1, 2, 5AC, and 6 were examined on 56 cell block sections and 26 follow-up pancreatectomy specimens. RESULTS: MUC1 and 6 expression was found in nonneoplastic pancreatic samples, whereas there was an absence of expression of MUC2 and 5AC. MUC2 was detected in mucosal goblets cells of the duodenum, MUC6 in Brunner glands, and MUC5AC in gastric foveolar cells. MUC5AC expression in differentiating ductal adenocarcinomas from benign conditions demonstrated better operating characteristics than either MUC1 or MUC6. The apomucin expression pattern both in cytology and follow-up surgical pathology specimens was similar. In surgical pathology specimens, the panel of 3 antibodies, MUC1+/MUC2-/MUC5AC+, was noted in 15 of 17 ductal carcinomas (88.2%). In nonneoplastic pancreatic tissue, the expression panel MUC1+/MUC2-/MUC5AC- was observed in 14 of 17 (82.4%) cases. In cytology specimens, the combination of MUC1+/MUC2-/MUC5AC+ was noted in 21 of 30 ductal carcinoma cases (70.0%), 3 of 6 atypical cases (50%), and 1 of 1 suspicious for malignancy cases (100%). The combination MUC1+/MUC2-/MUC5AC+ was not observed in any of the negative for malignancy or reactive cases (0 of 6). CONCLUSIONS: The most optimal panel for the diagnosis of ductal adenocarcinoma in both the EUS-FNA specimens is a panel including MUC1/MUC2/MUC5AC, whereas a panel of all 4 antibodies (MUC1, 2, 5AC, and 6) will in addition aid in differentiating inadvertently sampled normal/reactive duodenal and gastric epithelium from neoplastic pancreatic tissue.