Large lobular,low onco result

Hi lovely ladies .I’m trying to find out if anybody on here has had an onco type dx test done for a large lobular.?..Mine was 6.5 cm and node neg…test came back as low risk of recurrence so didn’t have to have chemo…just worried how it can be low risk when it’s large…?? I’ve had mastectomy,reconstruction and now on arimadex Rachael xx