What does cancer look like on an mri?

See below: This depends on the type of cancer and where it occurs. Usually, however, it shows up as a growth/mass and tends have tissues that light up with the intravenous contrast/dye. Sometimes it causes what's called "mass effect". Eg, a brain tumor may cause normal brain tissues to be displaced and compressed; a pancreas mass may cause obstruction of bile flow & thus jaundice, etc.

It depends: Cancer can look different depending on what part of the body that it occurs.