Molecular features of colorectal hyperplastic polyps and sessile serrated adenoma/polyps from Korea. Am J Surg Pathol. 2011;35:1274-1286. [PMID: 21836485 DOI: 10.1097/pas.0b013e318224cd2e]

Prolapse-related changes are a confounding factor in misdiagnosis of sessile serrated adenomas in the rectum

The differential diagnosis of rectal serrated polyps is challenging due to its unique anatomic location, the evolving concept of serrated polyps over the past several years, and to histologic changes seen in rectal mucosal prolapse. We reclassified 95 rectal polyps diagnosed originally as "sessile serrated adenoma" (SSA), "serrated polyp," or "hyperplastic polyp (HP) with features of SSA" in a 5-year period based on World Health Organization classification criteria for colorectal serrated polyps. BRAF (V600E) mutation assay was performed to explore its value in the differential diagnosis for serrated polyps. Twenty-six originally diagnosed SSAs were reclassified as SSA (15/26, 57.7%), HP with mucosal prolapse (HP-P; 7/26, 26.9%), and HP (4/26, 15.4%). Fifty-two polyps originally diagnosed "HP with features of SSA" were reclassified as HP-P (24/52, 46.2%), HP (10/52, 19.2%), inflammatory-type polyp (5/52, 9.6%), and serrated polyp unclassifiable (13/52, 25.0%). Thirty-one of the 78 originally diagnosed SSA or HP with features of SSA were reclassified as HP-P, which accounted for 32.6% of the rectal polyps in this study. Mucosal prolapse along with chronic inflammation and tissue embedding artifact were the most common features that led to misdiagnosis in rectal serrated polyps. BRAF mutation was identified in 8 of 11 HP, 4 of 4 SSA, and 8 of 11 unclassifiable serrated polyp of the rectum, and was absent in control tissue. Thus, histopathologic changes suggesting prolapsed rectal mucosa should take precedence over BRAF results.

Proximal colon cancers and the serrated pathway: a systematic analysis of precursor histology and BRAF mutation status

Although the serrated neoplasia pathway is thought to give rise to the majority of sporadic microsatellite instability-high (MSI-H) colon cancer, the exact proportion of these tumors that arise from serrated precursors has not been fully studied. Tubular and tubulovillous adenomas with features of the serrated neoplasia pathway have been described, and unlike sessile serrated adenomas, these lesions lack BRAF mutations. The contribution of these adenomas to sporadic MSI-H colon cancer is unclear. To this end, we conducted an analysis of right-sided sporadic MSI-H and microsatellite stable (MSS) colon cancer, with emphasis on precursor lesions. Overall 25% (19/75) of MSI-H colon cancer had a precursor, of which only 4 were recognized histologically as arising from a sessile serrated adenoma, and the remaining were best classified as adenomas. Of the 31 (of 89) MSS colon cancers with a precursor, only 1 was a sessile serrated adenoma (P=0.06). Histological analysis of the precursor adenomas to sporadic MSI-H colon cancer demonstrated a high frequency of crypt serrations compared with MSS colon cancer (93 vs 36%, P<0.001). BRAF mutations were found in 57/75 (76%) sporadic MSI-H and 10/89 (11%) MSS colon cancers (P<0.001). Molecular analysis demonstrated BRAF mutations in 11/12 adenoma and 3/3 sessile serrated adenoma precursors adjacent to BRAF-mutated MSI-H colon cancer. Similarly, all 4 precursors to BRAF-mutated MSS colon cancer were also BRAF mutated. The presence of BRAF mutations in these adenomatous precursors suggests that they represent sessile serrated adenomas with complete cytologic dysplasia. Finally, patients with sporadic MSI-H colon cancer were more likely to harbour synchronous sessile serrated adenomas (20 vs 8%; P=0.023). This is the largest study to rigorously evaluate the precursor and synchronous lesions in patients with right-sided colon cancer. Detailed molecular and histological analysis of these lesions confirms the importance of serrated precursors in the development of sporadic MSI-H colon cancer.

Wnt signalling pathway in the serrated neoplastic pathway of the colorectum: possible roles and epigenetic regulatory mechanisms

The role of Wnt signalling in the serrated neoplastic pathway of colorectal tumourigenesis appears to be heterogeneous. Wnt pathway abnormalities contribute to the progression of at least a subset of traditional serrated adenomas of the colorectum, but may play a less active role in its pathogenesis compared with that in conventional adenoma-carcinoma. However, immunohistochemical studies of β-catenin in sessile serrated adenomas have shown wide variability, producing conflicting results on Wnt signalling activation in sessile serrated adenomas. DNA methylation, involving APC, SFRPs and mutated in colorectal cancer (MCC), may bridge the mutational gap of APC or β-catenin for activating Wnt signalling in serrated adenomas of the colorectum.

Expression of Abelson interactor 1 (Abi1) correlates with inflammation, KRAS mutation and adenomatous change during colonic carcinogenesis

Background

Abelson interactor 1 (Abi1) is an important regulator of actin dynamics during cytoskeletal reorganization. In this study, our aim was to investigate the expression of Abi1 in colonic mucosa with and without inflammation, colonic polyps, colorectal carcinomas (CRC) and metastases as well as in CRC cell lines with respect to BRAF/KRAS mutation status and to find out whether introduction of KRAS mutation or stimulation with TNFalpha enhances Abi1 protein expression in CRC cells.

Methodology/Principal Findings

We immunohistochemically analyzed Abi1 protein expression in 126 tissue specimens from 95 patients and in 5 colorectal carcinoma cell lines with different mutation status by western immunoblotting. We found that Abi1 expression correlated positively with KRAS, but not BRAF mutation status in the examined tissue samples. Furthermore, Abi1 is overexpressed in inflammatory mucosa, sessile serrated polyps and adenomas, tubular adenomas, invasive CRC and CRC metastasis when compared to healthy mucosa and BRAF-mutated as well as KRAS wild-type hyperplastic polyps. Abi1 expression in carcinoma was independent of microsatellite stability of the tumor. Abi1 protein expression correlated with KRAS mutation in the analyzed CRC cell lines, and upregulation of Abi1 could be induced by TNFalpha treatment as well as transfection of wild-type CRC cells with mutant KRAS. The overexpression of Abi1 could be abolished by treatment with the PI3K-inhibitor Wortmannin after KRAS transfection.

Conclusions/Significance

Our results support a role for Abi1 as a downstream target of inflammatory response and adenomatous change as well as oncogenic KRAS mutation via PI3K, but not BRAF activation. Furthermore, they highlight a possible role for Abi1 as a marker for early KRAS mutation in hyperplastic polyps. Since the protein is a key player in actin dynamics, our data encourages further studies concerning the exact role of Abi1 in actin reorganization upon enhanced KRAS/PI3K signalling during colonic tumorigenesis.

Prospective, randomized, back-to-back trial evaluating the usefulness of i-SCAN in screening colonoscopy

BACKGROUND

The newly developed i-SCAN application can theoretically maximize the effectiveness of colonoscopy. However, the practical usefulness of the i-SCAN application during screening colonoscopy has not been assessed.

OBJECTIVE

To assess the efficacy of the i-SCAN application during screening colonoscopy.

DESIGN

A prospective, randomized trial that used a modified, back-to-back colonoscopy.

SETTING

Academic hospital.

PATIENTS

This study involved 389 asymptomatic, consecutive, average-risk patients who underwent screening colonoscopy.

INTERVENTION

The patients were randomized to the first withdrawal with either conventional high-definition white light (HDWL group; n = 119), i-SCAN contrast/surface enhancement (CE/SE) mode (i-SCAN1 group; n = 115), or i-SCAN CE/SE/tone enhancement-colorectal mode (i-SCAN2 group; n = 118). All patients underwent a second examination with HDWL as the criterion standard.

MAIN OUTCOME MEASUREMENTS

The primary outcome measurement was the adenoma detection rate and adenoma miss rate. The secondary outcome measurement was the accuracy of the histologic prediction of neoplastic and nonneoplastic polyps.

RESULTS

The adenoma detection rates during the first withdrawal of HDWL, i-SCAN1, and i-SCAN2 were 31.9%, 36.5%, and 33.1%, respectively (P = .742), and the adenoma miss rates of each group were 22.9%, 19.3%, and 15.9%, respectively (P = .513). Based on the multivariate analysis, the application of i-SCAN was not associated with an improvement in adenoma detection and the prevention of missed polyps. However, the prediction of neoplastic and nonneoplastic colorectal lesions was more precise in the i-SCAN2 group compared with the HDWL group (accuracy 79.3% vs 75.5%, P = .029; sensitivity 86.5% vs 72.6%, P = .020; and specificity 91.4% vs 80.6%, P = .040).

LIMITATIONS

Single-center trial.

CONCLUSION

i-SCAN during the screening colonoscopy may fail to improve adenoma detection and the prevention of missed polyps, but i-SCAN appears to be effective for real-time histologic prediction of polyps compared with conventional HDWL colonoscopy. (

CLINICAL TRIAL REGISTRATION NUMBER

NCT01417611.).

Colorectal serrated adenocarcinoma shows a different profile of oncogene mutations, MSI status and DNA repair protein expression compared to conventional and sporadic MSI-H carcinomas

Molecular characterization has been extensively studied in serrated polyps but very little is known in serrated adenocarcinomas (SACs). We analyzed the incidence of KRAS, BRAF and PIK3CA mutations, microsatellite instability (MSI) status and loss of the DNA repair proteins MLH1, MSH2, MSH6 and MGMT in a series of 89 SAC, 81 matched conventional carcinomas (CC) and 13 sporadic colorectal cancer showing histological and molecular features of high-level MSI (sMSI-H). Our results demonstrate that KRAS are more prevalent than BRAF mutations in SAC (42.7% vs. 25.8%; p = 0.011) being the KRAS-mutated cases even more abundant in SAC displaying adjacent serrated adenomas (51%). G12D and E545K are the most common KRAS and PIK3CA mutations found in SAC, respectively. SAC show higher frequency of MGMT loss compared to CC (50.6% vs. 25.3%; p = 0.001) especially in distal colon/rectum (60.0% vs. 21.6%; p = 0.0009). SAC differ from sMSI-H in terms of KRAS and BRAF mutation prevalence, MSI status and MLH1 expression (p = 0.0003, p < 0.0001, p < 0.0001, p < 0.001, respectively). SACs are more often KRAS-mutated and microsatellite stable and display different molecular and immunohistochemical characteristics compared to CC and sMSI-H.

Outcomes of a 5-year follow-up of patients with sessile serrated adenomas

OBJECTIVE

Sessile serrated adenomas (SSAs) are precursors to colorectal cancer (CRC). The purpose of this study is to determine the occurrence of new polyps and CRC in patients with an SSA over a 5-year follow-up interval.

METHODS

This study is a retrospective chart review of patients with SSAs diagnosed at colonoscopy in 2005. Abstracted information included patient demographics, colonoscopy information, and polyp characteristics.

RESULTS

During 2005, 34 SSAs and 5 mixed SSAs were identified in 33 patients. The mean patient age was 66 years and 58% were female. There was a family history of CRC in 45%, prior polyps in 33%, and previous CRC in 15%. The mean SSA size was 11 mm. SSAs were located proximal to the splenic flexure in 70%. Low-grade dysplasia was present in 3% of SSAs and 80% mixed SSAs. Synchronous adenomatous and hyperplastic polyps occurred respectively in 45% and 21%. High-grade dysplasia was present in 12% of the adenomas. Twenty-two patients underwent subsequent colonoscopies with 20 new SSAs and 1 mixed SSA identified. In SSAs low-grade dysplasia occurred in 10% and high-grade dysplasia in 5%. Low-grade dysplasia was present in the mixed SSA. Synchronous adenomatous and hyperplastic polyps occurred respectively in 45% and 37%. High-grade dysplasia was present in 10% of adenomas and CRC occurred in 1 (5%) patient.

CONCLUSIONS

SSAs occurred more frequently in females and in the right colon. Dysplasia occurred in a small subset of SSAs. There was a high rate of prior and subsequent CRC in patients with SSAs.

Genetic and epigenetic traits as biomarkers in colorectal cancer

Colorectal cancer is a major health burden, and a leading cause of cancer-related deaths in industrialized countries. The steady improvements in surgery and chemotherapy have improved survival, but the ability to identify high- and low-risk patients is still somewhat poor. Molecular biology has, over the years, given insight into basic principles of colorectal cancer initiation and development. These findings include aberrations increasing risk of tumor development, genetic changes associated with the stepwise progression of the disease, and errors predicting response to a specific treatment. Potential biomarkers in colorectal cancer are extensively studied, and how the molecular aberrations relate to clinical features. Yet, little of this knowledge has been possible to transfer into clinical practice. In this review, an overview of colorectal cancer genetics will be given, as well as how aberrations found in this tumor type are proposed as biomarkers for risk prediction, as diagnostic tools, for prognosis or prediction of treatment outcome.

The CpG island methylator phenotype may confer a survival benefit in patients with stage II or III colorectal carcinomas receiving fluoropyrimidine-based adjuvant chemotherapy

Background

Colorectal carcinoma (CRC) with CpG island methylator phenotype (CIMP) is recognized as a distinct subgroup of CRC, and CIMP status affects prognosis and response to chemotherapy. Identification of CIMP status in CRC is important for proper patient management. In Eastern countries, however, the clinicopathologic and molecular characteristics and prognosis of CRCs with CIMP are still unclear.

Methods

A total of 245 patients who underwent their first surgical resection for sporadic CRC were enrolled and CIMP status of the CRCs was determined using the quantitative MethyLight assay. The clinicopathologic and molecular characteristics were reviewed and compared according to CIMP status. In addition, the three-year recurrence-free survival (RFS) of 124 patients with stage II or stage III CRC was analyzed in order to assess the effectiveness of fluoropyrimidine-based adjuvant chemotherapy with respect to CIMP status.

Results

CIMP-high CRCs were identified in 34 cases (13.9%), and were significantly associated with proximal tumor location, poorly differentiated carcinoma, mucinous histology, and high frequencies of BRAF mutation, MGMT methylation, and MSI-high compared to CIMP-low/negative carcinomas. For patients with stage II or III CIMP-low/negative CRCs, no significant difference was found in RFS between those undergoing surgery alone and those receiving surgery with fluoropyrimidine-based adjuvant chemotherapy. However, for patients with CIMP-high CRCs, patients undergoing surgery with fluoropyrimidine-based adjuvant chemotherapy (n = 17; three-year RFS: 100%) showed significantly better RFS than patients treated with surgery alone (n = 7; three-year RFS: 71.4%) (P = 0.022).

Conclusions

Our results suggest that selected patients with CIMP-high CRC may benefit from fluoropyrimidine-based adjuvant chemotherapy with longer RFS. Further large scale-studies are required to confirm our results.