Cancer cells in Lump after chemo

Hello.

I am trying to find out from my doctors what the implications are when they found cancer cells in the lump removed from the breast AFTER I'd had chemo. The margins are clear - had no cancer cells in them - but the lump itself still had some.

My surgeon said it means the chemo didn't kill all the cancer, so they worry. She actually said "we worry" and stopped there. She didn't say anything else.

Has anyone else had cancer that the initial chemo didn't kill completely? What did it mean for your treatment and prognosis?

Thank you for any understanding support.