Cancer grows and changes, that is what makes it so scary. If the second scan shows abnormalities, go with that. Don't worry too much about why the information is now different. There are so many stories of missed, botched, misread, ignored diagnosis here it would make you weep with frustration.
Personally, I've had two critically delayed diagnosis and there is sweet nothing I can do except be thankful I finally got to the stage where the tumours were identified. I don't even know why we say 'thankfully'. It is a weird World. No wonder you are confused, keep hammering away until you have a clearer picture.