乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)的(de)(de)(de)(de)病(bing)(bing)(bing)因(yin)(yin)(yin)尚未完全清楚，研(yan)究發現(xian)乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)的(de)(de)(de)(de)發病(bing)(bing)(bing)存在(zai)一定(ding)的(de)(de)(de)(de)規律(lv)性(xing)，具有(you)(you)乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)高(gao)危(wei)(wei)因(yin)(yin)(yin)素(su)(su)(su)的(de)(de)(de)(de)女性(xing)容(rong)易(yi)患(huan)(huan)乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)。所(suo)謂高(gao)危(wei)(wei)因(yin)(yin)(yin)素(su)(su)(su)是指(zhi)與乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)發病(bing)(bing)(bing)有(you)(you)關的(de)(de)(de)(de)各種危(wei)(wei)險因(yin)(yin)(yin)素(su)(su)(su)，而(er)大多數乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)患(huan)(huan)者都具有(you)(you)的(de)(de)(de)(de)危(wei)(wei)險因(yin)(yin)(yin)素(su)(su)(su)就(jiu)稱為(wei)乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)的(de)(de)(de)(de)高(gao)危(wei)(wei)因(yin)(yin)(yin)素(su)(su)(su)。據中(zhong)(zhong)國(guo)腫瘤登記年(nian)報顯示：女性(xing)乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)年(nian)齡(ling)(ling)別發病(bing)(bing)(bing)率0～24歲(sui)(sui)年(nian)齡(ling)(ling)段處較(jiao)低(di)水(shui)平，25歲(sui)(sui)后(hou)逐漸(jian)(jian)上升(sheng)，50～54歲(sui)(sui)組(zu)達到高(gao)峰，55歲(sui)(sui)以后(hou)逐漸(jian)(jian)下降(jiang)。乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)家族史是乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)發生的(de)(de)(de)(de)危(wei)(wei)險因(yin)(yin)(yin)素(su)(su)(su)，所(suo)謂家族史是指(zhi)一級親屬(母親,女兒,姐妹)中(zhong)(zhong)有(you)(you)乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)患(huan)(huan)者。近年(nian)發現(xian)乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)腺(xian)(xian)(xian)(xian)體致密(mi)也(ye)成為(wei)乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)的(de)(de)(de)(de)危(wei)(wei)險因(yin)(yin)(yin)素(su)(su)(su)。乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)的(de)(de)(de)(de)危(wei)(wei)險因(yin)(yin)(yin)素(su)(su)(su)還(huan)有(you)(you)月經(jing)初(chu)潮早（<12歲(sui)(sui)），絕經(jing)遲（>55歲(sui)(sui)）；未婚，未育，晚育，未哺乳(ru)(ru)(ru)；患(huan)(huan)乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)良性(xing)疾病(bing)(bing)(bing)未及(ji)時診治(zhi)；經(jing)醫院活檢(活組(zu)織檢查)證實(shi)患(huan)(huan)有(you)(you)乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)非典型(xing)增生；胸(xiong)部接受過高(gao)劑量(liang)(liang)放射線(xian)的(de)(de)(de)(de)照射；長期服用外源(yuan)性(xing)雌激素(su)(su)(su)；絕經(jing)后(hou)肥胖(pang)；長期過量(liang)(liang)飲酒；以及(ji)攜帶與乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)相關的(de)(de)(de)(de)突變基因(yin)(yin)(yin)。需要(yao)解釋的(de)(de)(de)(de)是乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)的(de)(de)(de)(de)易(yi)感基因(yin)(yin)(yin)歐、美國(guo)家做了大量(liang)(liang)研(yan)究，現(xian)已(yi)知(zhi)的(de)(de)(de)(de)有(you)(you)BRCA-1、BRCA-2，還(huan)有(you)(you)p53、PTEN等，與這些基因(yin)(yin)(yin)突變相關的(de)(de)(de)(de)乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)稱為(wei)遺傳性(xing)乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)，占全部乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)的(de)(de)(de)(de)5%～10%。具有(you)(you)以上若干項高(gao)危(wei)(wei)因(yin)(yin)(yin)素(su)(su)(su)的(de)(de)(de)(de)女性(xing)并不一定(ding)患(huan)(huan)乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)，只能說(shuo)其患(huan)(huan)乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)的(de)(de)(de)(de)風險比正常人高(gao)，中(zhong)(zhong)國(guo)婦(fu)女乳(ru)(ru)(ru)腺(xian)(xian)(xian)(xian)癌(ai)(ai)(ai)的(de)(de)(de)(de)發病(bing)(bing)(bing)率還(huan)是低(di)的(de)(de)(de)(de)。