I ve small pain in my left breast, left armpit & back(left side). can dis b a symptom of breast cancer(no cancer history in my family) i am 21 female?

Highly Unlikely: Sorting out different causes of breast pain starts with determining if the pain is coming from the breast tissue or the chest wall. Favoring the former includes variation w/menstrual cycle; favoring the latter is relation to activity and post-menopausal state. I recommend that you see your gyne or primary care dr. To help sort thru this. Good luck.

Very unlikely: It would be extremely unusual, but not impossible, for this to be a breast cancer. Any persistent symptom in the breast, and certainly any mass, should be examined by a doctor. You may need to have an ultrasound of the area done. It is always better to look into these things than ignore them.

Probably not: Pain is not a common symptom of breast cancer. Additional it would be rare of a 20 year to develop breast cancer. However you should see your primary care physician to report these symptoms.