How often are colon polyps malignant? what if the polyps was causing bloody stool?

Rarely...: Unless you have familial polyposis syndrome, risk of malignant colon polyps at 28 years old is small. In older patients, the vast majority of polyps are non-malignant. Polyps may bleed, & at 28 the possibility of juvenile retention polyposis must be considered. However, bleeding per rectum at your age more typically runs the spectrum from hemorrhoids & anal fissures to crohn's/colitis & infection.

1-3%: Approx 20% of patients >50 years old have adenomatous polyps (potentially precancerrous).The vast majority of colon polyps are benign, but if they remain in the colon for a long time(>10 years) they have the potential to progress to a cancer.Both benign and cancerous polyps can cause blood y stools all patients with blood with bm should be examined.