Child Sexual Abuse is any form of unwanted direct sexual contact or touching, non-touching exposure to sexual activities or pornography for the purpose of personal sexual gratification by the perpetrator.

Statistics vary; however, about 15% to 25% of women and 5% to 15% of men were sexually abused when they were children. Approximately 90% of the offenders have some familiarity with their victim; 30% are relatives and 60% are other acquaintances.

Signs of sexual abuse in a teenager:

 

The 3 starred * signs are often seen in teenage girls as strong indicators that they have been or are currently being sexually abused.

This list gives parents an idea of what to look for if you suspect your teenager has been sexually abused. Communicate with your teen. If a teenager says they were or are being sexually abused, they are typically telling the truth. It is important to get them help.

Reference:
https://www.childwelfare.gov/pubs/usermanuals/sexabuse/sexabusec.cfm
http://en.wikipedia.org/wiki/Sexual_abuse