Freaking out. Internal mammary node

I was diagnosed with a cancer in the 4 o'clock position right breast not far from intramammary nodes. My concern was about these nodes. When surgery was done they injected dye etc into nipple which travelled to sentinel nodes under arm. But if injected into cancer would it have gone to intramammary or underarm. I asked surgeon and oncologist re the intramammary nodes and was told not to worry.  Once I start Arimidex after radiotherapy that any cancer cells remaining should reduce/disappear.