Breast cancer is a largely unknown disease until today, despite the fact that it affects almost ten percent of the women above the age of forty years all over the world. The causes of this killer cancer are not known even after decades of research into it. Similarly it is unknown why some women have higher chances of getting breast cancers than others.

Though the causative factors are not known, some risk factors have been identified. There is no medical proof why these factors make the disease more probable, but this is a study of observation. In a vast cross-section of women with the observed risk factors, it has been found that the chances of getting breast cancers are very high.

The various risk factors for breast cancer are as follows:-

(1) Family History of Breast Cancer

If a near relative like a mother or a sister has had breast cancer, then there is a very high chance that the cancer will occur sometime in life. This propensity is observed even if far relatives such as cousins and aunts have had breast cancer, though the chances are lesser as the relatives are more removed. Even if a male relative has had breast cancer or prostate cancer, then there is a chance of getting breast cancer. This clearly indicates that breast cancer runs through family lines through inheritance. Certainly the chances are very high if more than one family member has had breast cancer.

(2) Personal History of Breast Cancer

If a woman has had breast cancer in the past, then there is a great chance that the breast cancer may recur. This is true even if the cancer had been removed in its benign stage itself. Sometimes the cancer cells spread into the nearby lymph. This makes a possibility that the cancer will occur in the opposite breast. In fact, women who have had cancer in one breast have 50 to 75% more chances of developing the cancer in the other breast.

(3) Diseases of the Breast

Several breast diseases can increase the chances of having breast cancer. Changes in the cells of the breasts can lead to atypical hyperplasia. This condition can cause a three to fourfold increase in the possibility of getting breast cancer in the later years. This risk also exists if the atypical hyperplasia has occurred in other women of the family. Another such condition is the benign breast tumor condition known as fibro adenoma. However, women with fibrocystic breasts generally do not have any added vulnerability to breast cancer. Yet, such conditions could make the breasts lumpy and hide the real tumors (if any) during mammography.

(4) Lifestyle

In today's world, lifestyle is the single largest contributing factor for the proliferation of breast cancer among women. Several elements of the lifestyle have been found to be directly accordant with the prevalence of breast cancer. Smoking and alcoholism in women are among the chief factors. Even diet has been pointed out as an important risk factor. Women who consume a diet with more high-cholesterol fats in them have higher chances of breast cancer. At the same time leading a sedentary lifestyle without indulging much in physical activity are also potentially dangerous.

(5) Radiation

It has been found that women who undergo radiation therapies in their chest region at a young age have an increased risk of developing breast cancer in their later lives. Radiation therapy is generally prescribed for women with conditions like Hodgkin's disease or non-Hodgkin's lymphoma. So women who have undergone such treatments may get breast cancer in their later years.

(6) Hormonal Imbalances
There are several factors that can change the hormone balance of the body. Some of them are:-
a) Beginning the menstrual cycle early, i.e. before the age of twelve years,
b) Having the first pregnancy after the age of thirty years,
c) Having no pregnancy at all,
d) Having a late menopause.
All these conditions can increase the level of estrogen in the body. This increases the risk of getting breast cancer to a mild extent. Apart from that women who take regular birth control pills, breast enhancement supplements, antidepressants and antihistamines and hormone modifying supplements stand at a higher risk to get breast cancers.

The above are the major risk factors for breast cancers. But since the study on breast cancers is not yet complete, the above is by no means a complete list. There are several other indications of breast cancers, like breast implant operations; but these have not yet been confirmed. The implants used in the earlier days were made of silicone gels. These were riskier in terms of breast cancer. However, nowadays the silicone gel implants have been replaced by saline implants. This has reduced the risk to a great extent.

It must be also noted that women have much higher chances of getting breast cancer than men. In fact, most people think that breast cancer is a disease that affects only women. This is not true. Men also get breast cancers, but to a much lesser degree than women. Also, age is a very important factor. The chances of getting breast cancer are much higher when the woman has crossed the age of 50 years.