Doctor test my breast tumor tissue n say it wasn't cancer. could it be possible turn into cancer and how? what should i eat to not make it worst?

First,...: ...Unless you have a strong family history, the odds of a young girl to have breast cancer are low. Second, you can have all sorts of findings in a breast biopsy. Some can progress to cancer down the line and some do not. Ask the md who ordered the biopsy about its implications. Finally, eat well, exercise, don't smoke and limit alcohol intake. Enjoy your life with awareness, not fear.

Diet no relation: Diet is not related to breast cancer. It is very rare a breast malignancy at your age. The main risk is in family, mother, sister, breast cancer, mainly if the malignancy happened in premenopausal age. Also history of ovarian cancer. Early menarch with late menopause, obesity. Benign conditions do not become cancers.Self examination sould be done.