Would a transvaginal ultra sound detect cervical cancer?

Only if advanced. A pap smear is the best way to screen for cervical cancer. A biopsy of the cervix is the way to diagnose cervical cancer or precancerous cells. Most abnormal cells on the cervix are precancerous, only a few are actual cancer when found. Most cervical cancers are early and small, so aren't seen by an ultrasound. An ultrasound could only see cervical cancer if it was causing a large mass.