How did Hannah Montanas mom die from?

in the show her mom died not in real life!she died after she became Hannah Montana it clearly states that in suite life on deck with Hannah Montana when she looses the ankelet she says to lilly my mom gave me this before my first show so im not sure how she died but i think she knew she was gonna die cuz in he could be the one the video that her mom was in she said i knew i wouldn't be around so i think it was of cncer or something