Hello @kdgranger and welcome to the NETs support group on Mayo Connect. I am glad that you found this forum and that you are posting your questions and concerns. When we are dealing with a rare form of cancer, like NETs, it is helpful to find others who have experienced this same thing, isn't it?

You mentioned that you had surgery 12 years ago for a NET in your colon. Is that correct? It appears that you have also had surgery for a NET in your breast. Was this a lumpectomy? Was there any other treatment for the breast NET?

You might want to read through the posts in the following discussions where members have had NETs in the breast.
https://connect.mayoclinic.org/discussion/ned-of-breast/
and
https://connect.mayoclinic.org/discussion/neuroendocrine-cells-in-breast-and-lungs-dipnech/?commentsorder=newest#chv4-comment-stream-header
I can understand your concern regarding this new NET in the colon. Please remember that it is always the patient's right to get a second opinion, whenever you feel the need. If you do get a second opinion, I highly recommend that you consult with a NET specialist. Mayo Clinic has NET specialists at all there of their locations. If you would like an appointment at Mayo Clinic for a consultation, here is the link that will help you get an appointment, https://connect.mayoclinic.org/discussion/ned-of-breast/.

If an appointment at Mayo is not a possibility, for any reason, here is a list of NET specialists worldwide,

https://www.carcinoid.org/for-patients/treatment/find-a-doctor/. On this list, NET specialists are listed by state and then by country.

Seeing a NET specialist, either by a virtual or by an in-person appointment can help you feel more confident about your current medical treatment. Often, after a consultation with a NET specialist, you can then follow up with your current oncologist.

Have you considered getting a second opinion in order to determine if the "watch and wait" approach for this new NET is the best option?