I'm so sorry to hear of your recurrence, Andrea. I was diagnosed around the same time as you in 2016 and I remember your story very well and reading all of your messages.
Yes, there are other things that can cause lymph nodes to enlarge, like a mild infection or illness. I had a few enlarged nodes on my original staging MRI scan which thankfully turned out not to be cancerous. How distant is it? You say it is a colon lymph node. My understanding is that it would still be considered a local recurrence if a colon lymph node is cancerous.
Wishing you all the best and hoping for some positive scan results.
Male, 33 @ dx, stage 1 RC (T1N0M0 0/29 LNs)
2016-02 - Cancerous polyp removed during colonscopy, 0.5 mm margin
2016-03 - ULAR & TME surgery, temp ileostomy
2016-04 - DVT, pulmonary embolism
2016-11 - Ileostomy reversal
2018-10 - Another DVT & PE