Cancers have common traits: spreading uncontrollably, metastasizing - these are what make cells cancerous. But cells from different specialized tissues tend to

Cancers have common traits: spreading uncontrollably, metastasizing - these are what make cells cancerous. But cells from different specialized tissues tend to become cancerous in different ways, by expressing different genes. So a treatment that targets a particular gene expression may work for one type but not others. And a cancer that returns after treatment will have yet a different gene expression (usually resistant to that particular treatment). Like the Borg, cancer adapts. That's why it's called the Emperor of all maladies: http://www.pbs.org/show/story-cancer-emperor-all-maladies/ http://www.pbs.org/show/story-cancer-emperor-all-maladies/