Abstract. Colorectal cancer (CRC) is one of the most frequent cancers worldwide. Adenoma is the main precursor lesion and, recently, the serrated polyps were described as a group of colorectal lesions with malignant potential. The morphologic and biologic characterizations of serrated polyps remain limited. The aim of the present study was to determine the frequency of KRAS and BRAF mutations and microsatellite instability (MSI) in CRC precursor lesions, to evaluate the association between molecular, pathologic and morphologic alterations in precursor lesions and to compare with the alterations detected in CRC. A series of 342 precursor lesions were removed from 155 patients during colonoscopy. After morphologic classification, molecular analysis was performed in 103 precursor lesions, and their genetic profile compared with 47 sporadic CRCs. Adenomas were the main precursor lesions (70.2%). Among the serrated polyps, the main precursor lesion was hyperplastic polyps (HPs) (82.4%), followed by sessile serrated adenomas (12.7%) and traditional serrated adenomas (2.0%). KRAS mutations were detected in 13.6% of the precursor lesions, namely in adenomas and in HPs, but in no serrated adenoma. BRAF mutations were found in 9 (8.7%) precursor lesions, mainly associated with serrated polyps and absent in adenomas (P<0.001). High MSI (MSI-H) was absent in precursor lesions. In the 47 CCR cases, 46.8% exhibited KRAS mutation, 6.5% BRAF mutations and 10.6% MSI-H. This study confirms the role of KRAS and BRAF mutations in CRC carcinogenesis, a crucial step in implementing CRC screening strategies.

Crystallization proceeds through high-temperature and non-stoichiometric phases which recrystallize to become sanbornite (BaSi2O5) during heating or through time.

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We report here the analysis of vibrational properties of the sanbornite (low-BaSi2O5) and Ba5Si8O21 using theoretical and experimental approaches, as well as results of high temperature experiments up to 1100-1150˚C. The crystal parameters derived from Rietveld refinement and calculations show excellent agreement, within 4%, while the absolute mean difference between the theoretical and experimental results for the IR and Raman vibrational frequencies was <6 cm-1. The temperature-dependent Raman study renders that both sanbornite and Ba5Si8O21 display specific Ba and Si sites and their Ba-O and Si-O bonds. In the case of the stretching modes assigned to specific Si sites, the frequency dependence on the Si-O bond length exhibited very strong correlations. Both phases showed that for a change of 0.01 Å, the vibrational mode shifted 10 ± 2 cm-1. These results are promising for using Raman spectroscopy to track in situ reactions under a wide variety of conditions, especially during crystallization.