Appendiceal cancer (malignancies of the appendix, a small tissue pouch that is part of the gastrointestinal tract) is very rare, occurring in perhaps one or two people per 1 million per year. Prognoses are mixed, with a 5-year survival rate of 67 to 97 per cent for low-grade tumours detected early, but much lower for advanced cases that may have spread to other parts of the body.