Early-stage colon cancer may cause no noticeable discomfort; the most common first clue is a persistent change in bowel habits—diarrhea, constipation, or alternating patterns lasting more than two weeks. Stools become narrower, pencil-shaped, or are coated with mucus or blood, which may appear dark red or bright red. As the tumor grows, vague lower-abdominal cramping or bloating worsens after meals; if the lumen narrows, colicky pain and progressive distension develop. Systemic features include unexplained weight loss, fatigue, pallor from chronic blood loss, and low-grade fever. A hard, fixed mass may be palpable in the right or left lower quadrant. Perforation... Learn more