Cancer incidence, and prevalence are now five. Cancer mortality remains one. As diagnostic means become more and more refined, more slowly growing tumors are detected. Some require decades to reach the upper cancer death line, and are relatively harmless, yet they are included in the statistics. This is known as length bias.
Genetic methods reveal six tumors.
Prevalence and incidence are now 6, more tumors were detected at an earlier stage, yet the overall tumor biology did not change. In other words, a young female with a BRCA1 gene may carry a slow growing tumor without any clinical significance. Take for instance incidental tumors that are less dangerous to the patient than overt tumors. The two tumor types cannot be equated, or pooled together. Each tumor type poses a certain threat to the patient, and this important information is not accounted for by epidemiology.