BackgroundFlat adenomas are a subgroup of colorectal adenomas that have been associated with a distinct biology and a more aggressive clinical behavior compared to their polypoid counterparts. In the present study, we aimed to compare the mutation spectrum of 14 cancer genes, between these two phenotypes.MethodsA consecutive series of 106 flat and 93 polypoid adenomas was analyzed retrospectively for frequently occurring mutations in “hot spot” regions of KRAS, BRAF, PIK3CA and NRAS, as well as selected mutations in CTNNB1 (β-catenin), EGFR, FBXW7 (CDC4), PTEN, STK11, MAP2K4, SMAD4, PIK3R1 and PDGFRA using a high-throughput genotyping technique. Additionally, APC was analyzed using direct sequencing.Results APC mutations were more frequent in polypoid adenomas compared to flat adenomas (48.5% versus 30.3%, respectively, p = 0.02). Mutations in KRAS, BRAF, NRAS, FBXW7 and CTNNB1 showed similar frequencies in both phenotypes. Between the different subtypes of flat adenomas (0-IIa, LST-F and LST-G) no differences were observed for any of the investigated genes.ConclusionThe lower APC mutation rate in flat adenomas compared to polypoid adenomas suggests that disruption of the Wnt-pathway may occur via different mechanisms in these two phenotypes. Furthermore, in contrast to previous observations our results in this large well-defined sample set indicate that there is no significant association between the different morphological phenotypes and mutations in key genes of the RAS-RAF-MAPK pathway.
Urban a Background. The management and prognosis of subepithelial tumors (SETs) of the upper gastrointestinal tract depend on the correct preoperative evaluation, including tissue diagnosis in selected cases. Several methods providing deep tissue sampling for cytological and/or histological examinations have been described but their diagnostic yield and precise position in the diagnostic algorithm remain to be established. This prospective randomized study aims to compare the Endosonography-Guided Fine-Needle Aspiration (EUS-FNA) to KeyHole Biopsy (KHB) in cytological or histological diagnostics of upper gastrointestinal SETs. Patients and Methods. This study was conducted in a single tertiary endoscopy center in Ostrava, Czech Republic between November 2010 and October 2015. Patients with endoscopically detected SETs of the upper gastrointestinal tract with a diameter ≥ 2 cm, were randomized to either the EUS-FNA with 22G needle, or to the Key Hole biopsy (forceps biopsy through mucosal incision) groups. The main study outcomes were success rate of tissue diagnostics and, in the cases of Gastrointestinal Stromal Tumours (GIST), possibility of determining mitotic activity. A cross-over examination was performed in situations where the first method had failed. Results. A total of 46 consecutive patients were randomized. Of these, 24 (52%) and 22 (48%) were randomized to EUS-FNA group and KHB arm, respectively. 5 SETs (11%) were detected in the esophagus, 40 (87%) in the stomach and 1 (2%) in the duodenum. The definitive diagnosis was established by the first sampling method in 42 (91%) patients, including 22 (92%) in the EUS-FNA group and 20 (91%) in the KHB group (P=0.999), and after a cross-over in another 3 (7%) patients. The most prevalent SET was GIST (70%). Although some mitotic activity could be observed in 11 patients, the mitotic index could be diagnosed in none of them. Of a total of 20 surgically treated patients, preoperative and postoperative tissue diagnosis corresponded in 19/20 (95%) cases, including 100% in FNA group and 91% in KHB group (P=0.999). No adverse events of tissue sampling occurred in the study. Conclusions. Deep tissue sampling by EUS-FNA and KHB are equally effective in the diagnostics of SETs of the upper gastrointestinal tract ≥ 2 cm. However, neither EUS-FNA nor KHB provided adequate tissue sample to determine mitotic index. Trial Registration: Clinicaltrials.gov (NCT02025244).
BackgroundNonpolypoid adenomas are a subgroup of colorectal adenomas that have been associated with a more aggressive clinical behaviour compared to their polypoid counterparts. A substantial proportion of nonpolypoid and polypoid adenomas lack APC mutations, APC methylation or chromosomal loss of the APC locus on chromosome 5q, suggesting the involvement of other Wnt-pathway genes. The present study investigated promoter methylation of several Wnt-pathway antagonists in both nonpolypoid and polypoid adenomas.MethodsQuantitative methylation-specific PCR (qMSP) was used to evaluate methylation of four Wnt-antagonists, SFRP2, WIF-1, DKK3 and SOX17 in 18 normal colorectal mucosa samples, 9 colorectal cancer cell lines, 18 carcinomas, 44 nonpolypoid and 44 polypoid adenomas. Results were integrated with previously obtained data on APC mutation, methylation and chromosome 5q status from the same samples.ResultsIncreased methylation of all genes was found in the majority of cell lines, adenomas and carcinomas compared to normal controls. WIF-1 and DKK3 showed a significantly lower level of methylation in nonpolypoid compared to polypoid adenomas (p < 0.01). Combining both adenoma types, a positive trend between APC mutation and both WIF-1 and DKK3 methylation was observed (p < 0.05).ConclusionsMethylation of Wnt-pathway antagonists represents an additional mechanism of constitutive Wnt-pathway activation in colorectal adenomas. Current results further substantiate the existence of partially alternative Wnt-pathway disruption mechanisms in nonpolypoid compared to polypoid adenomas, in line with previous observations.
Purpose: Flat adenomas are a subgroup of colorectal adenomas that have been associated with a more aggressive clinical behavior compared with their polypoid counterparts. Here, we aimed to compare one of the molecular changes most explicitly associated with adenoma to carcinoma progression, that is, chromosomal instability, between flat and polypoid colorectal adenomas.Experimental Design: Consecutive series of 83 flat and 35 polypoid adenomas were analyzed for DNA copy number changes using a high-resolution array comparative genomic hybridization platform, microsatellite instability (MSI) status, and for mutations in the adenomatous polyposis coli (APC) gene. Immunohistochemical stainings for CD3, CD8, and FoxP3 expression were carried out.Results: Patterns of DNA copy number changes differed between the two phenotypes, with significantly more frequent loss of 5q14.3 and 5q15-q31.1 in flat adenomas, whereas losses of 1p36.32-p35.3, 10q25.3, 17p12, and chromosome 18 were more frequent in polypoid adenomas (false discovery rate < 0.2). MSI was observed in one flat adenoma. As the 5q15-q31.1 region harbors the APC locus, APC mutation status was investigated, showing significantly less mutations in flat adenomas (P ¼ 0.04). An initial exploration of a possible association of 5q loss with inflammation indicated that tumor-infiltrating lymphocytes were more abundant in the stroma of flat adenomas compared with that of polypoid adenomas.Conclusion: Flat and polypoid adenomas have partially distinct chromosomal profiles, consistent with differences in the biology underlying these phenotypes. Alterations more specific to flat adenomas, in particular 5q loss, may be associated with inflammation.
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