Cases reported "Colonic Neoplasms"

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11/12. Drastic genetic instability of tumors and normal tissues in Turcot syndrome.

    Turcot syndrome is characterized by an association of malignant brain tumors and colon cancer developing in the patient's teens. Since the mechanism of carcinogenesis in Turcot syndrome is still unclear, we analysed genetic changes in tumors from a Turcot patient with no family history of the condition. All tumors, including one astrocytoma, three colon carcinomas, and two colon adenomas, exhibited severe replication error (RER), and all colon tumors showed somatic mutations at repeated regions of TGFbetaRII, E2F-4, hMSH3, and/or hMSH6 genes. Somatic APC mutations were detected in three of three colon carcinomas, and somatic p53 mutations were detected in the astrocytoma and two of three colon carcinomas, both of which showed two mutations without allele loss. We also found that normal colon mucosa, normal skin fibroblasts and normal brain tissue from this patient showed respective high frequencies of RER, in contrast to usual HNPCC patients in which RER was very rare in normal tissues. These results suggest that extreme dna instability in normal tissues causes the early development of multiple cancer in Turcot syndrome. A missense mutation (GAG to AAG) at codon 705 of hPMS2 gene was detected in one allele of this patient, which was inherited from his mother without tumors. Additional unknown germline mutation may contribute to the genetic instability in normal tissues.
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keywords = carcinogenesis
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12/12. Multifocal neoplasia involving the colon and appendix in ulcerative colitis: pathological and molecular features.

    A patient with ulcerative colitis, extensive dysplasia, multifocal colon cancer, and an appendiceal cystadenoma is described. A 48-year-old man with a 26-year history of ulcerative colitis (UC) had extensive dysplasia involving nearly the entire colon and four dysplasia-associated mass lesions (DALMs). Four invasive adenocarcinomas were present. This case is the first documentation of a DALM (mucinous cystadenoma) arising in the appendix in the setting of UC. The genetic alterations present in the various lesions were analyzed. The molecular profiles of the neoplastic lesions differed. Mutations were found in p53 and ras genes, and one site showed microsatellite instability in a single genetic locus. These molecular abnormalities develop before invasive cancer develops, and may undergo clonal expansion to create large mucosal patches containing certain cells with genetic alterations. The diversity of the early changes suggests that the recurrent inflammation characteristic of long-standing UC randomly damages genes known to participate in colon carcinogenesis and that it affects multiple target genes. The findings also support a multiclonal origin of synchronous tumors because the molecular phenotypes of the preinvasive lesions differed at various sites.
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keywords = carcinogenesis
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