Stage 1B, beginning radiation and 2 very tiny lung nodules found..,anything to worry about?

Hi. I am posting this for my Mom. She is still learning how to use a discussion board so I'm helping. Mom is 64, uterine cancer was unexpectedly found after vaginal hysterectomy. Because of that, lymph nodes were not sampled. Cancer was invasive adenocarcinoma, and was confined to uterus as far as we know but was 80% into uterus muscle. Gym Onc said he was confident it did not reach lymph nodes and did a ct scan. Staged at 1B (used to be called 1C). Said if Mom had no treatment he would give her an 80% chance of no reoccurrence and if she did radiation 90-96% chance of no reoccurrence. Mom decided to have 25 external treatments and 3 internal. They start next week.

Here is our question, met with the local radiation oncologist who will be doing the external treatments. She said results of the radiologist report of the ct scan from a couple weeks ago looked good. No apparent lymph nodes issues. But she did note there were 2 very tiny lung nodules, one was about 2mm and the other was about 4mm. She said they are nothing to worry about and they will just keep an eye on them. Called our radiation oncologist at UK and had them look over then. They called us back and said they are so tiny they are nothing to be concerned over and the chance they have anything to do with Mom's cancer is "remote". That's all good but how can they be sure it isn't cancer that had spread or something? Any ideas or advice?

Thank you so much.