A novel classification system for breast cancer based on normal breast cell phenotypes and various expression levels of estrogen receptor (ER), androgen receptor (AR), and vitamin D receptor (VDR). The various categories of the classification system are associated with different survival rates and prognoses. The invention includes a method of classifying breast cancer comprises measuring the levels of ER, AR, and VDR in the cancerous tissue, and classifying the breast cancer into one of the above-noted categories according to expression levels. The invention includes a method of predicting the prognosis of breast cancer in a patient and a method of determining a treatment regimen for breast cancer depending on the category in which the breast cancer is classified. The invention includes a method of treating breast cancer according to the expression profile of ER, AR, and VDR detected in the cancerous tissue. Kits for detecting the same are also provided.
