A 70-year-old man presents with fatigue, weight loss, abdominal pain, and ove blood in the stools. A complete blood count reveals anemia with hemoglobin of 10 g/dL. A colonoscopy and subsequent colonic biopsy reveal adenocarcinoma. Which of the following is the most likely predisposing lesion/disorder that lead to this malignancy?

The patient is most likely a case of sporadic colon cancer. Familial Adenomatous Polyposis (FAP) syndrome: Colorectal adenocarcinoma develops in 100% of untreated FAP patients, often before age 30 and nearly always by age 50. Hyperplastic polyps: These lesions are without malignant potential. Hereditary non-polyposis colorectal cancer (HNPCC) syndrome: Colon cancers in HNPCC patients tend to occur at younger ages than sporadic colon cancers and are often located in the right colon. Adenocarcinoma of colon Develops through a progression of mutations in oncogenes & tumor suppressor genes in a multistep process. Normal mucosa evolves into tubular adenoma with malignant potential-carcinoma (Adenoma-Carcinoma sequence) Majority of sporadic colon cancers (70-80%) follow this sequence and usually have cancers of left colon Rest of the sporadic cases have defects in DNA mismatch repair or DNA hypermethylation (arise from serrated adenoma and develop more commonly in right colon). Carcinoma of rectosigmoid (left-sided) colon-Early obstruction, with change in bowel habits & decreased caliber of stool. Carcinoma of right colon (right-sided)-Present late, with Iron deficiency anemia d/t chronic blood loss from lesion.