Is.6 cm maglinant breast cancer considered small? easily treatable?

Yes and no: in general yes it is if there is no metastases to the regional lymph nodes, so the bottom line depen (penicillamine) on the staging from 1-5. and the treatment for the original cancer will dictate the need for other treatment like chemotherapy, and radiation therapy. the lower the stage the higher chance of survival.

Good news, but...: A 0.6 cm tumor usually has a very good prognosis once excised, but there are no certainties. I am VERY glad you found it early. Best wishes.