PIK3CA and breast cancer: Whilst this may seem counterintuitive, this could be related to the fact that the molecular composition of the tumors defined as PIK3CA wild-type is unknown- in other words, there are probably multiple other means of PI3K pathway activation that exist in this group– or that low as opposed to high levels of pathway activation could be enough in the luminal breast cancer subtype for reasons yet to be fully understood- ie for example, too high levels may result in senescence.