How fast is my cancer growing?

Hi was diagnosed with stage 2A grade 3 breast cancer on Friday 9th Feb and currently waiting for my plan which will take about 2 weeks. My cancer is 3cm. How long is it growing whilst I'm waiting? I will then have to wait to start chemo how big will it be then?? May sound silly but do we know how quick these cells can increase?

Thank you in advance and sorry I'm probably paranoid.