There are no fixed reasons for breast cancer however the classic reason for breast cancer is the presence of a lump in the breast or the armpit. Breast cancer like other cancers occurs due to the interaction between environment and a defective gene.
According to Vinay Aggarwal, Internal medicine Physician, cedarsSinai Hospital, Los Angeles, breast cancer is genetic. If you have any family history of breast cancer then you have strong chances to have the disease.