I do agree with Japdip - the internet is full of studies of various types and often reading through these, instead of providing us with helpful insight, causes unnecessary fear and anxiety.
The most important piece of information that you need right now, has already been provided by Radiology that they feel there is nothing to worry about.
But, at this point, you still do have other options open to you.
Get another second opinion. Sometimes doing this is definitely worth the money spent as it gives peace of mind. Breast Cancer is scary, it does cause fear and seeing another clinic could help ease your concerns.
The other option you have, is to request another mammogram at 6 months, rather than wait for the entire 12 months.
Hope this helps
It's true that mammary nodes are not unusual ... if the node were found to be terribly enlarged or showed some other indication I'm sure a biopsy would have been recommended. If you stop reading so much perhaps you can relax .... tracking the size of the node of course will be noted on your next Mammogram. Regards ...