Human breast cancer and sexual activities

Several studies have reported that high-risk human papillomaviruses (HPVs) are present in more than 50% of human breast cancers ( Yu et al, 2000 ; Liu et al, 2001 ; Damin et al, 2004 ; de Villiers et al, 2005 ; Kan et al, 2005 ; Lawson et al, 2006a , 2006b ; Yasmeen et al, 2007a , 2007b ). Furthermore, high-risk HPVs of the same type were found in both cervical and breast cancer of the same patients ( Hennig et al, 1999 ; Widschwendter et al, 2004 ). This finding has led to the hypothesis that HPVs could be transmitted to the breast through sexual activities ( Kan et al, 2005 ; Lawson et al, 2006a , 2006b ). Consequently, it is possible that the incidence of HPV-positive breast cancer in young women is related to high-risk HPV genital infections, which are much more common in young women who have multiple sexual partners ( IARC, 1995 ).