My gf has a small lump under her chin right in the middle. it's firm, does not move and has no pain. she is worried it's cancer?

See MD: Area involved may be nothing more than an infected lymph node, associated with a skin irritation or infection. There may also be a dental infection. At any rate the patient should be seen by her doctor to determine what if anything needs to be done. At least have the area measured, maybe an ultrasound and a check of her neck and thyroid. Do not take chances.