This may sound like a strange question. But could a Cancerous cell be transferred from one person to another from Oral contact e.g. Through Saliva, or other exchange of bodily fluids? I know that other diseases from Bacteria / Viral can be transferred in this way, but does the same apply to Cancerous cells? - or would the recipient's body just breakdown and destroy the cancerous cells?
Cancer is successful at killing it's victims because it is genetically still very similar to the host. The immune system does not respond to it sufficiently to eradicate the mutated cells and this allows it to grow out of control.
When dealing with any kind of transmittal this would be close to an organ donation. Without a very close match, and Immunosuppressants the body will "reject" any cancer cells, and wipe them out. Saying this here have been freak incidents where in an organ transplant scenario, cancer was transmitted.