Cancerous Polyp bowel

I am 67 year old woman, had breast cancer at 40 and 45 have been relatively healthy since. I have been symptom free of what is written below.

I had a 7x5 cm polyp removed two weeks ago. Have been told that 2 out of the 3 layers that were dissected are cancerous. It was a flat polyp. Told 8% chance of spread. So 92% chance of no spread. Trying to view this as good news despite feeling anxious. CT scan next week and the meeting with consultant to discuss further options. Because I was a bit thrown by the phone call I didn't ask two questions.

Q1 if two thirds were cancerous would those be the top two thirds , so would the third that was against the wall of the bowel be clear. (I had breast cancer 27 years ago and this was how it was presented) and if that is the case does that greatly reduce the chance of spread.

Q2 can a CT scan pick up cancer in lymph nodes and if not how will they know those are clear? The consultant said that's what they needed to make sure of, no spread to lymph nodes. And second part to this question is I am overweight will the CT scan be affected by that?