neo90 It can be so hard to make these decisions :(
I had a different situation to you as I had a lumpectomy for a 10mm tumour that was grade 1 (slow growing) and it was ER+ PR+ HER2-. I had 3 out of 4 lymph nodes involved.
The multidisciplinary team found my situation unusual and recommended axillary dissection. That dissection of 6 lymph nodes found no involvement.
I then had radiation because I'd had the lumpectomy and number of lymph nodes involved. Now hormone therapy.
Chemo wasn't suggested to me due to the grade, size and type of my tumour. So I didn't need the onco test.
If chemo had been on the table I would have been trying to ask them why specifically in my case and, unless they had a superstrong case, I would have looked at doing the onco test to help with my decision making.