11/27/2023 0 Comments Apple diagnostics via nbiCpG island methylator phenotype (CIMP): global hypermethylation of CpG islands → silencing of MMR gene expression.Hypermethylation phenotype pathway in colon cancer.Microsatellite instability pathway in colon cancer: due to methylation or mutations in mismatch repair genes ( MMR genes, e.g., MLH1 or MSH2).Most cases of sporadic CRC develop via this pathway.APC gene mutation (loss of cellular adhesion and increased cellular proliferation ) → KRAS gene mutation (unregulated cellular signaling and cellular proliferation ) → TP53 and DCC gene mutation.Chromosomal instability pathway in colon cancer : The adenoma-carcinoma sequence is the progressive accumulation of mutations in oncogenes (e.g., KRAS ) and tumor suppressor genes (e.g., APC, TP53 ) that results in the slow transformation of adenomas into carcinomas.As the incidence of CRC is high, screening for CRC is recommended for all individuals, starting at 45–50 years of age (earlier in high-risk individuals).Ĭolorectal carcinogenesis pathways (molecular pathology) Surveillance following CRC treatment is essential to identify and manage recurrence and/or metastases. In addition, for cancer stages ≥ II, chemotherapy is required for colon cancer and chemotherapy and/or radiation therapy for rectal cancer. The type and extent of resection depend on the stage of the cancer. Curative surgical resection of colorectal cancers and metastases is preferred when feasible. Staging of the cancer is necessary to evaluate the extent of disease and determine the appropriate management. Complete colonoscopy with histopathologic analysis confirms the diagnosis. Since the introduction of screening with direct visualization or stool-based testing, early-stage carcinomas have become easier to diagnose in asymptomatic patients. These features as well as iron deficiency anemia in men older than 50 years of age and postmenopausal women are red flags for CRC. Clinical signs are often nonspecific and may include a change in bowel habits, lower GI bleeding, and weight loss. Most colorectal cancers (95%) are adenocarcinomas. Risk factors include a positive family history, hereditary syndromes, diet, and a number of conditions, such as inflammatory bowel disease. Colorectal cancer ( CRC) is the fourth most commonly diagnosed cancer in the United States.
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