DIFFUSION

  1. Colon Carcinoma The model of stepwise genetic alterations in cancer is best illustrated by observation of colonic lesions at different stages of progression to malignancy. Certain genetic alterations are found commonly in early-stage adenomas, whereas others tend to occur more frequently at later stages of tumorigenesis or after the development of invasive carcinoma. The timeline of genotypic and phenotypic changes during the development of colon cancer .These changes are in keeping with the concept that serial phenotypic changes, driven by serial genetic alterations, must occur in a cell for it to exhibit full malignant (invasive and metastatic) properties. The earliest molecular defect in the pathogenesis of colon cancer is activation of the Wnt signaling pathway, which occurs through the development of somatic mutations in the APC tumor suppressor gene in the normal colonic mucosa. This leads to abnormal cell proliferation and the initial steps in neoplasia that lead to fo...