So my hubby had precancerous cells during a colonoscopy and he is only 36 so yes, it does happen, BUT - he went for a colonoscopy because he has had crazy amount of issues - not talking just a bit of blood - if he hadn't had something wrong I'd have been shocked. So, of your only issue is the blood, trust me there is still hope, and if it is colon cancer, take heart in that it takes about ten years to fully develop I to cancer, and the pre cancer, once it is removed for biopsy, it is gone! It is highly treatable if caught early, and if this is your first symptom and you are under 40, IF you do have cancer it is likely to be early on and you will be fine.