Decreased anti-parietal cell antibody titer in the advanced phase of autoimmune gastritis.

BACKGROUND: Autoimmune gastritis (AIG) is histologically classified into three phases according to the severity of oxyntic mucosal atrophy: early, florid, and end phases. This study aimed to clarify the relationship between the AIG phase and the anti-parietal cell antibody titer. METHODS: Patients who underwent upper gastrointestinal endoscopy were retrospectively reviewed in this study. We enrolled patients who were histologically diagnosed with AIG and serologically tested for anti-parietal cell antibody (APCA). AIG patients were classified into three groups: early, florid, and end phase groups. Clinical characteristics, including APCA titers, were compared among these three groups. RESULTS: A total of 44 AIG patients were enrolled. There were two patients in the early phase, 11 in the florid phase, and 31 in the end phase. APCA-positive rates were 100% in the early phase, 90.9% in the florid phase, and 90.3% in the end phase. The mean APCA titer was 480 U in the early phase, 220 U in the florid phase, and 150 U in the end phase. There was a stepwise decrease in the APCA titer from the early phase to the end phase. The mean APCA titer for the end phase was significantly lower than that of the early phase or florid phase. Additionally, there was a stepwise decrease in serum gastrin levels from the early phase to the end phase. CONCLUSION: AIG progresses from the early phase to the end phase, and the APCA titer shows a decrease. The negativity of APCA could occur, especially in the end phase.

Clue of Diagnosis for Autoimmune Gastritis.

BACKGROUND: The diagnostic clues for autoimmune gastritis (AIG) can be classified into 2 categories: endoscopic findings and pathological diagnosis. We believe that research on the AIG detection rate by endoscopists could provide a better understanding of the diagnosis of AIG. This study aimed to clarify the ratio of the endoscopic and the pathological diagnoses of AIG. METHODS: We retrospectively reviewed consecutive patients who underwent esophagogastroduodenoscopy (EGD). During their first EGD, the gastric mucosa with C2 atrophy or more was biopsied for pathological evaluation based on the updated Sydney system. A gastric biopsy was also performed after Helicobacter pylori eradication, obtaining specimens from at least 2 sites, the greater curvature of the corpus and the antrum. We enrolled patients who were positive for the anti-parietal cell antibody and were diagnosed with AIG, histologically and/or endoscopically. The detection rates of AIG were compared between endoscopic diagnosis and pathological diagnosis. RESULTS: A total of 10,822 patients underwent EGD during the study period. Finally, 41 patients with AIG were enrolled, leading to an AIG prevalence of 0.38% in this study. As for the clue leading to AIG detection, 31.7% (13/41) were diagnosed through endoscopy (proximal-predominant atrophy), and 68.3% (28/41) were diagnosed pathologically. The AIG detection rate by endoscopists in the posteradication group was significantly lower than in the H. pylori-negative group (p < 0.05). CONCLUSION: Endoscopists frequently overlooked AIG, especially in posteradication cases. Pathological assessment using the updated Sydney system after H. pylori eradication might be a promising strategy to detect AIG better.

Endoscopic gastric atrophy is strongly associated with gastric cancer development after Helicobacter pylori eradication.

BACKGROUND: Risk factors for gastric cancer during continuous infection with Helicobacter pylori have been well documented; however, little has been reported on the risk factors for primary gastric cancer after H. pylori eradication. We conducted a retrospective, endoscopy-based, long-term, large-cohort study to clarify the risk factors for gastric cancer following H. pylori eradication. METHODS: Patients who achieved successful H. pylori eradication and periodically underwent esophagogastroduodenoscopy surveillance thereafter at Toyoshima Endoscopy Clinic were enrolled. The primary endpoint was the development of gastric cancer. Statistical analysis was performed using the Kaplan-Meier method and Cox's proportional hazards models. RESULTS: Gastric cancer developed in 15 of 1232 patients. The cumulative incidence rates were 1.0 % at 2 years, 2.6 % at 5 years, and 6.8 % at 10 years. Histology showed that all gastric cancers (17 lesions) in the 15 patients were of the intestinal type, within the mucosal layer, and <20 mm in diameter. Based on univariate analysis, older age and higher endoscopic grade of gastric atrophy were significantly associated with gastric cancer development after eradication of H. pylori, and gastric ulcers were marginally associated. Multivariate analysis identified higher grade of gastric atrophy (hazard ratio 1.77; 95 % confidence interval 1.12-2.78; P = 0.01) as the only independently associated parameter. CONCLUSIONS: Endoscopic gastric atrophy is a major risk factor for gastric cancer development after H. pylori eradication. Further long-term studies are required to determine whether H. pylori eradication leads to regression of H. pylori-related gastritis and reduces the risk of gastric cancer.

Prognostic significance of the lymph node ratio in stage IV colorectal cancer patients who have undergone curative resection.

BACKGROUND: The lymph node ratio (LNR) was proposed as a prognostic indicator in Stage III colorectal cancer (CRC) patients in recent studies. The purpose of this study was to evaluate the prognostic impact of the LNR in Stage IV CRC patients who have undergone curative resection. METHODS: A retrospective review of 119 Stage IV CRC patients who underwent curative resection in our institute from 1997 to 2009 was performed. Patients were divided into two groups (low LNR and high LNR) by means of their median LNR. A disease-free survival (DFS) and an overall survival (OS) were analyzed using the Kaplan-Meier curve; multivariate analysis was performed using the Cox proportional hazard model. RESULTS: The cutoff value for the LNR was 0.111. For the entire study group, the 5-year DFS was 22 % and the 5-year OS was 65 %. DFS was not significantly different between patients in the low LNR group and the high LNR group (25 and 19 %, respectively; P = 0.317), but OS was significantly higher in the low LNR group patients compared with the high LNR group patients (77 and 54 %, respectively; P < 0.001). Using multivariate analysis, we identified the LNR as an independent prognostic factor for OS, with a hazard ratio of 3.08 (95 % CI 1.38-8.19; P = 0.005). CONCLUSIONS: LNR is a potent prognostic indicator for stratification in Stage IV CRC patients who have undergone curative resection.

Giant solitary fibrous tumor of the pelvis successfully treated with preoperative embolization and surgical resection: a case report.

Solitary fibrous tumors (SFTs) rarely develop in the pelvis. When they do arise, they are usually treated using surgery, although SFTs are often very large by the time of diagnosis, which makes surgical excision difficult. We report a case of a 63-year-old man who was referred to our hospital for the treatment of a giant tumor of the pelvis. Computed tomography (CT) revealed a 30 × 25 × 19 cm sized hypervascular tumor that almost completely filled the pelvic cavity. The diagnosis of SFT was made by CT-assisted needle biopsy. The feeding arteries of the tumor were embolized twice. The first embolization aimed to reduce the tumor volume, while the second one was planned a day prior to the surgery to obtain hematostasis during the operation. Tumor resection was then performed. The blood loss during the operation was 440 ml, and there was no uncontrollable bleeding. The postoperative course was uneventful. No recurrence of SFT was observed during a 2-year follow-up.

Alpha-fetoprotein-producing early rectal carcinoma: a rare case report and review.

BACKGROUND: Alpha-fetoprotein (AFP)-producing rectal cancer is very rare, and this type of cancer frequently metastasizes to the liver with a poor prognosis. To date, only 11 cases of AFP-producing colorectal cancer have been reported. CASE PRESENTATION: A 41-year-old woman was first presented to the hospital for anal bleeding. An elevated tumor with a central shallow depression in the lower rectum was detected by colonoscopy. Transanal excision was performed, and the histology revealed adenocarcinoma. Further immunohistopathological examination revealed that the tumor was an AFP-producing adenocarcinoma of the rectum. Although local resection was performed 2 months before the diagnosis of AFP tumor, the serum AFP level was normal. The depth of the submucosal invasion was 5,000 µm, and there was venous invasion. Also, no lymphatic invasion was detected. Therefore, additional surgical resection with lymph node dissection was conducted, and the patient underwent laparoscopic intersphincteric resection. No residual cancer was identified in the surgical specimens, and there was no evidence of lymph node metastasis. The patient was discharged 18 days postoperatively, and 12 months after the operation, there are no signs of recurrence. CONCLUSION: To the best of our knowledge, this is the first case of an AFP-producing rectal cancer that was diagnosed at an early stage.

Clinical Characteristics and Postoperative Complications of Patients Undergoing Emergency Surgery for Ulcerative Colitis.

BACKGROUND/AIMS: Despite recent advances in medical therapy, the role of surgery for severe ulcerative colitis remains important and determining the timing and indications for colectomy are difficult for both gastroenterologists and surgeons. We compared the clinical characteristics and postoperative complications of emergency surgeries for ulcerative colitis to those of elective surgeries. METHODOLOGY: We retrospectively examined 77 patients with ulcerative colitis who underwent colectomy without cancer or dysplasia in our institute in 1989-2012. Clinicopathological features, cytomegalovirus involvement, and postoperative complications were evaluated. RESULTS: Twenty-seven patients underwent emergency surgeries and the other 50 underwent elective surgeries. Emergency surgeries were performed significantly earlier in the disease course than elective surgeries. Postoperative complications were more frequent in emergency surgeries than in elective surgeries. Those who underwent emergency surgeries with relative indications tended to develop postoperative complications more frequently when intensive long-term steroid therapy was introduced. CONCLUSIONS: Emergency surgeries were associated with frequent postoperative complications. For refractory severe ulcerative colitis, cytomegalovirus involvement should be determined and prolonged steroid therapy is associated with postoperative complications; therefore, early treatment decisions are important.

Nuclear Notch3 expression is associated with tumor recurrence in patients with stage II and III colorectal cancer.

BACKGROUND: The importance of Notch signaling in colorectal cancer (CRC) tumorigenesis has been recently recognized. However, the significance of Notch3 expression and its association with Notch1 expression in CRC is unclear. In the present study, we investigated Notch1 and Notch3 expression in Stage II and III CRC to assess their association with clinicopathological characteristics. METHODS: The protein expression of Notch1 and Notch3 was examined using immunohistochemistry in 305 CRC specimens. Nuclear expression of Notch1 and Notch3 and their associations with clinicopathological characteristics and distant relapse-free survival (dRFS) were evaluated. RESULTS: Nuclear Notch1 was overexpressed in 37 % of specimen, and nuclear Notch3 in 38 %. Nuclear Notch3 expression correlated with tumor differentiation status (P = 0.0099). Nuclear expression of Notch1 and Notch3 was associated with tumor recurrence (P = 0.0311 and P = 0.0053, respectively). In multivariate analysis, nuclear Notch3 expression [hazard ratio (HR) = 1.71; 95 % confidence interval (CI), 1.06-2.78; P = 0.0271), lymph node metastasis, and venous involvement were independently correlated with dRFS. In subgroup analysis, nuclear Notch3 expression was strongly associated with dRFS in Stage II CRC (HR = 3.47; 95 % CI 1.44-9.22; P = 0.0055). Both nuclear Notch1 and Notch3 were positive in 67 specimens (22 %) and both were negative in 144 specimens (47 %). Coexpression of nuclear Notch1 and Notch3 had an additive effect toward poorer dRFS compared with a negative subtype (HR = 2.48; 95 % CI, 1.41-4.40; P = 0.0019). CONCLUSIONS: Nuclear Notch3 expression might be a novel predictive marker for recurrence in Stage II and III CRC.

Prognostic impact of primary tumor resection and lymph node dissection in stage IV colorectal cancer with unresectable metastasis: a propensity score analysis in a multicenter retrospective study.

BACKGROUND: Retrospective studies have shown that primary tumor resection improves the prognosis of patients with colorectal cancer with unresectable metastasis (mCRC). Prognostic significance of lymph node dissection (LND) in mCRC has not been examined previously. The aim of this study was to investigate the prognostic impact of primary tumor resection and LND in mCRC. METHODS: A total of 1,982 patients with mCRC from January 1997 to December 2007 were retrospectively studied. The impact of primary tumor resection and LND on overall survival (OS) was analyzed using Cox proportional hazards model and propensity score analysis to mitigate the selection bias. Covariates in the models for propensity scores included treatment period, institution, age, sex, carcinoembryonic antigen, tumor location, histology, depth, lymph node metastasis, lymphovascular invasion, and number of metastatic organs. RESULTS: In a multivariate analysis, primary tumor resection and treatment in the latter period were associated with an improved OS, and age over 70 years, female sex, lymph node metastasis, and multiple organ metastasis were associated with a decreased OS. In the propensity-matched cohort, patients treated with primary tumor resection showed a significantly better OS than those without tumor resection (median OS 13.8 vs. 6.3 months; p = 0.0001). Furthermore, among patients treated with primary tumor resection, patients treated with D3 LND showed a significantly better OS than those with less extensive LND (median OS 17.2 vs. 13.7 months; p < 0.0001). CONCLUSIONS: It was suggested that primary tumor resection with D3 LND improves the survival of patients with mCRC.

Laparoscopic resection of a gastrointestinal stromal tumor of the lower rectum in a patient with coronary artery disease following long-term neoadjuvant imatinib treatment and anticoagulation therapy.

Surgery is the mainstay of treatment for gastrointestinal stromal tumors (GISTs). However, complete resection of rectal GISTs is sometimes difficult because of bulkiness and/or anatomical reasons. Neoadjuvant imatinib therapy has gained attention as an alternative treatment to increase the chance of en bloc resection of rectal GISTs, although it usually takes several months. In this case report, we first demonstrated that neoadjuvant imatinib therapy can be performed safely not only to downsize tumors, but also to allow adequate time for the effective treatment of major comorbid illnesses. A 74-year-old man was diagnosed with a 45 mm GIST of the lower rectum. He also had severe stenosis in the proximal segment of the left anterior descending coronary artery. Following the implantation of a drug-eluting stent, the patient received imatinib together with dual anti-platelet therapy for 12 months without obvious side effects. Follow-up image studies revealed tumor shrinkage as well as stent patency. En bloc resection of the GIST was performed laparoscopically, which preserved the anus. The patient is currently alive without any evidence of relapse for 12 months after surgery.

A case of extraperitoneal stoma-associated internal hernia after abdominoperineal resection.

Published reports concerning internal hernias after extraperitoneal stoma construction are scarce. In our present report, we describe the case of a 56-year-old man who was referred to our hospital for the treatment of rectal cancer. He underwent abdominoperineal resection of the rectum with sigmoidostomy using an extraperitoneal route. On the ninth postoperative day, the patient experienced sudden and intense abdominal pain and was diagnosed with strangulation of the small intestine due to a stoma-associated internal hernia. Therefore, an emergency laparotomy was performed. The surgical findings showed that the small intestine protruded through the space between the sigmoid colon loop and the abdominal wall in a cranial-to-caudal direction. The strangulated portion of the small intestine was recovered, and the orifice of herniation was closed. No recurrence of internal herniation was observed during the follow-up period.

FOLFOX as adjuvant chemotherapy after curative resection of distant metastases in patients with colorectal cancer.

OBJECTIVES: The prophylactic effect of FOLFOX regimen, a standard regimen for unresectable colorectal cancer (CRC), was investigated in the adjuvant setting of CRC cases with distant metastases. METHODS: The study population included 116 CRC patients with synchronous metastases and 91 patients with metachronous metastases who had undergone curative operation in our hospital between 2000 and 2009. Clinicopathological parameters of CRC, postoperative chemotherapeutic regimen, recurrence rate, and relapse-free survival (RFS) were analyzed retrospectively. RESULTS: After resection of CRC and synchronous metastases, 53 (84%) out of 63 patients without chemotherapy, and 38 (83%) out of 46 that received 5-fluorouracil (5-FU) alone or with leucovorin (LV) developed recurrent tumors. By contrast, only 1 (17%) among 6 patients who underwent FOLFOX treatment showed recurrence. The FOLFOX group exhibited significantly improved RFS as compared to the 5-FU (+ LV) or surgery-alone group (p = 0.03, p = 0.007, respectively). On the other hand, in patients with metachronous metastases, tumor-relapse rate and RFS were not significantly influenced by post-metastasectomy therapies. CONCLUSIONS: In this retrospective analysis, the adjuvant administration of FOLFOX appeared to reduce the risk of relapse in a small group of CRC patients with synchronous metastases. Prospective randomized trials will be required to confirm the benefits of this management strategy.

Gene expression of mesenchyme forkhead 1 (FOXC2) significantly correlates with the degree of lymph node metastasis in colorectal cancer.

In stage III colorectal cancer, patients with N1 stage tumors show poorer outcome than patients with N2 stage tumors. Our objective was to identify genes that are predictive for the presence of lymph node metastasis, and to characterize the aggressiveness of lymph node metastases. Gene expression profiles of colorectal cancer were determined by microarray in training (n = 116) and test (n = 25) sets of patients. We identified 40 discriminating probes in patients with and without lymph node metastases. Using these probes, we could predict the presence of lymph node metastasis with an accuracy of 87.1% (training set) and 76.0% (test set). Among discriminating probes, FOXC2 expression was significantly correlated with the degree of lymph node metastasis. FOXC2 was expressed significantly and disparately in patients with N1 and N2 stage tumors as analyzed by real-time reverse transcriptase-polymerase chain reaction. FOXC2 appears to be involved in determining the aggressiveness of lymph node metastasis in colorectal cancer.

[FOLFOX as adjuvant chemotherapy after curative resection of distant metastatic lesions in patients with colorectal cancer].

We investigated the effectiveness of prophylactic FOLFOX after curative resection of synchronous metastases in patients with colorectal cancer (CRC). Clinicopathological information including postoperative chemotherapy, such as a therapeutic regimen, relapse-free survival (RFS), site of recurrence, etc., was retrospectively analyzed in 116 CRC patients with synchronous distant metastases, and 63 patients with metachronous metastases who had received surgery in our hospital between 2000 and 2009. Fifty-three patients (84%) out of 63 without adjuvant chemotherapy, and 38 (83%) out of 46 patients that received oral or intravenous 5-fluorouracil (5-FU) (alone or with leucovorin (LV)or isovorin) developed recurrent tumor(s) afterwards. The median RFSs were 119 and 281 days, respectively. By contrast, a single patient among 6 who underwent FOLFOX (up to 12 therapeutic courses) showed recurrence 476 days after surgery. The RFS of the FOLFOX was significantly higher than that of the 5-FU (+LV) or surgery alone (p=0. 03, p=0. 007, respectively). In conclusion, the FOLFOX regimen is more beneficial for CRC patients with synchronous metastasis as adjuvant chemotherapy than 5-FU (+LV) or other followup strategies.

Simple feedback of colonoscopy performance improved the number of adenomas per colonoscopy and serrated polyp detection rate.

Background and study aims High-quality endoscopy requires improvement of not only the adenoma detection rate (ADR) but also the serrated polyp (SP) detection rate and the mean number of adenomas per positive procedure (MAP +). We evaluated whether a simple feedback of colonoscopy performance improves those quality indicators using propensity-score matching. Patients and methods Eleven endoscopists were evaluated regarding colonoscopy performance including ADRs, SP detection rates, mean numbers of adenomas per procedure (MAPs), and MAPs + with their ranking in the clinic. Endoscopic performance was compared before and after the feedback. Results Colonoscopies were performed for 874 patients before the feedback and 1,272 patients after the feedback. Using propensity-score matching, 803 patients before the feedback and 803 patients after the feedback were matched. ADR after the feedback was significantly higher than that before the feedback (50.8 % and 40.8 %, respectively). MAP after feedback was significantly larger than that before the feedback (0.92 and 0.69, respectively), as well as MAP + (1.96 and 1.69, respectively). Clinically significant SP detection rate was also improved from 10.0 % to 14.9 %. Conclusions Feedback including ADR, MAP, MAP +, and clinically significant SR detection rate could improve on those quality indicators. Further studies are needed to effectively prevent colorectal cancer in colonoscopy practice.

Filiform polyposis with sigmoid colon adenocarcinoma: a case report.

BACKGROUND: Filiform polyposis is a rare form of inflammatory polyposis, which is occasionally formed in the colon of patients with history of inflammatory bowel disease (IBD). It is characterized by presence of several to hundreds of slender, worm-like polyps in the colon lined by histologically normal colonic mucosa and often coalesce, resulting in a tumor-like mass. Filiform polyposis is most frequently associated with a post-inflammatory reparative process in patients with IBD history, and only cases of filiform polyposis occurring in patients without IBD history have been reported. Filiform polyposis has been considered as a benign inflammatory polyposis without any risk of dysplasia, while the possibility of carcinogenesis of inflammatory polyps is not fully excluded. To date, only three cases of filiform polyposis coexisting with dysplasia have been reported. CASE PRESENTATION: A 59-year-old male patient with no past medical history of IBD underwent laparoscopic sigmoidectomy for obstructive filiform polyposis, which was associated with sigmoid colon adenocarcinoma. Based on the histological findings of the resected specimen, invasive sigmoid colon adenocarcinoma was surrounded by filiform polyposis, and adenocarcinoma also scattered uniformly on the surface of filiform polyposis. In immunohistochemistry, abnormal p53 expression was observed in adenocarcinoma, while it was not shown in mucosa on filiform polyposis. CONCLUSIONS: This is the fourth case of filiform polyposis that is closely associated with colon dysplasia or adenocarcinoma based on histological findings. However, immunohistochemical findings did not support the theory that inflammation initiates adenocarcinoma in filiform polyposis like IBD. Hence, further immunohistochemical and genetic analyses are needed to clarify the association between filiform polyposis and carcinogenesis.

Gene expression signature and the prediction of ulcerative colitis-associated colorectal cancer by DNA microarray.

PURPOSE: Ulcerative colitis (UC) is associated with a high risk of colorectal cancer. To identify genes that could predict the development of cancer in UC, we conducted a DNA microarray analysis using nonneoplastic rectal mucosa of UC patients. EXPERIMENTAL DESIGN: Gene expression in nonneoplastic mucosa of 53 UC patients were examined. Gene expression profiles were examined using human Genome U133 Plus 2.0 gene chip array (Affymetrix). Among 53 UC patients, 10 had UC-associated cancer (UC-Ca group) whereas 43 did not (UC-NonCa group). RESULTS: By comparing gene expression profiles of nonneoplastic rectal mucosae between the UC-Ca and UC-NonCa groups, we could identify 40 genes that were differentially expressed between two groups. The list of discriminating genes included low-density lipoprotein receptor-related protein (LRP5 and LRP6). Previous studies suggested that LRP5 and LRP6 expression promotes cancer cell proliferation and tumorigenesis and are considered as candidate oncogenes. In the present study, both LRP5 and LRP6 showed significantly higher expression in the UC-Ca group, which suggests the importance of these genes in the development of UC-associated colorectal cancers. With the 40 selected discriminating genes, we did class prediction of the development of colorectal neoplasms in UC patients. Using the k-nearest neighbor method and the support vector machine, we could predict the development of UC-associated neoplasms with an accuracy of 86.8% and 98.1%, respectively. CONCLUSIONS: These findings have important implications for the early detection of malignant lesions in UC and may provide directions for future research into the molecular mechanisms of UC-associated cancer.

Silencing of secreted frizzled-related protein genes in MSI colorectal carcinogenesis.

BACKGROUND/AIMS: The epigenetic pathway of colorectal carcinogenesis has recently become the focus of attention. The most common epigenetic change is the promoter hypermethylation of tumor suppressor genes. Secreted frizzled-related proteins have been identified and are reported to act as inhibitors of the Wnt signaling pathway. It has also been reported that microsatellite unstable cancers show more frequent hypermethylation in tumor suppressor genes and less frequent APC mutation. METHODOLOGY: Fifty-one sporadic colorectal cancers were investigated, of which 22 were MSI-H and 29 were MSI-L/MSS. Methylation-specific polymerase chain reaction was performed to detect the methylation status of SFRP1, 2 and 5 genes. RESULTS: All of the samples showed hypermethylation in the promoter region of SFRP1. MSI-H cancers showed more frequent hypermethylation in SFRP2 than MSI-L/MSS cancers, though there was no statistical significance. SFRP5 promoter hypermethylation was significantly more frequent in MSI-H cancers than in MSI-L/MSS cancers. CONCLUSIONS: SFRPs may act as an important inhibitor of the Wnt signaling pathway in MSI-H cancers.

Distal colorectal cancers with microsatellite instability (MSI) display distinct gene expression profiles that are different from proximal MSI cancers.

Promoter methylation of the mismatch repair gene plays a key role in sporadic microsatellite instability (MSI) colorectal cancers. However, promoter methylation often occurs in proximal colon cancers, and molecular phenotypes underlying MSI cancers in distal colon have not been fully clarified. Our goal was to clarify the difference between MSI and microsatellite stability (MSS) cancers and, furthermore, to determine distinct characteristics of proximal and distal MSI cancers. By DNA microarray analysis of 84 cancers (33 MSI and 51 MSS), we identified discriminating genes (177 probe sets), which predicted MSI status with a high accuracy rate (97.6%). These genes were related to phenotypic characteristics of MSI cancers. Next, we identified 24 probe sets that were differentially expressed in proximal and distal MSI cancers. These genes included promoter methylation-mediated genes, whose expression was significantly down-regulated in proximal MSI cancers. Among discriminating genes between MSI and MSS, nine methylation-mediated genes showed down-regulation in MSI cancers. Of these, 7 (77.8%) showed down-regulation in proximal MSI cancers. Furthermore, methylation-specific PCR confirmed that frequency of hMLH1 promoter methylation was significantly higher in proximal MSI cancers (P = 0.0317). These results suggested that there is a difference between proximal and distal MSI cancers in methylation-mediated influence on gene silencing. In conclusion, using DNA microarray, we could distinguish MSI and MSS cancers. We also showed distinct characteristics of proximal and distal MSI cancers. The inactivation form of hMLH, per se, differed between proximal and distal MSI cancers. These results suggested that distal MSI cancers constitute a distinct subgroup of sporadic MSI cancers.