Yes, very true! I have a friend on here who that happened to and it turned cancerous! I'm not sure of all the exact details, but I know it does happen!
It is a possibility.
A molar pregnancy is when the egg is not fertilized correctly and the placenta develops into an abnormal mass of cysts. Once discovered, the molar pregnancy needs to be removed with a D&C and HCG levels monitored for 6-12 months to make sure no tissue has remained. If there is tissue remaining after this time it will grow again and cancer drugs may be required to destroy the abnormal tissue. In very rare cases, cancer can develop from the mole and spread to other organs (so removing the tissue with a D&C as soon as the mole is discovered is crucial as is treatment if the mole tissue has remained and growth persists after the D&C).
A women who has had a molar pregnancy should NEVER get pregnant until a year after the D&C to ensure that all tissue has been removed. If you got pregnant before a year then you are high risk and need to be monitored. If you got pregnant after that time frame and were monitored appropriately then you have a very low risk of having a problem (from the last mole) but seeing a specialist to be on the safe side is a good idea.