Cancer occurs as a result of mutations, or abnormal changes, in the genes responsible for regulating the growth of cells and keeping them healthy. The genes are in each cell’s nucleus, which acts as the “control room” of each cell. Normally, the cells in our bodies replace themselves through an orderly process of cell growth: healthy new cells take over as old ones die out. But over time, mutations can “turn on” certain genes and “turn off” others in a cell. That changed cell gains the ability to keep dividing without control or order, producing more cells just like it and forming a tumor.

The term “breast cancer” refers to a malignant tumor that has developed from cells in the breast. Usually breast cancer either begins in the cells of the lobules, which are the milk-producing glands, or the ducts, the passages that drain milk from the lobules to the nipple. Less commonly, breast cancer can begin in the stromal tissues, which include the fatty and fibrous connective tissues of the breast.

Breast cancer has been known to mankind since ancient times. It has been mentioned in almost every period of recorded history. Because of the visible symptoms especially at later stages the lumps that progress to tumors have been recorded by physicians from early times. This is more so because, unlike other internal cancers, breast lumps tend to manifest themselves as visible tumors.

Earlier, however, it was a matter of taboo and embarrassment that meant detection and diagnosis was rare. The mention of breast cancers in literature beyond medical journals and books was rare. Involvement of more women and actively bringing out the disease into the open is a recent phenomenon that is around three or four decades old. In the 1990’s the symbol of breast cancer - the pink ribbon – brought out a revolution against this cancer.

In 1713 Bernardino Ramazzini's developed a hypothesis that high frequency of breast cancer in nuns was due to lack of sex. Ramazzini said that without regular sexual activity, reproductive organs, including the breast may decay and develop cancers. Yet another researcher Friedrich Hoffman of Prussia postulated that women who had regular sex but still developed cancer were practicing “vigorous” sex. This could be leading to lymphatic blockage.