Theron will sport the limited edition of Marc Jacobs' Hanes T-shirt for a public service announcement to benefit Saks Fifth Avenue's 2004 Key to the Cure women's cancer initiative, Zap2it.com reported Thursday.
The ad will appear in major fashion and lifestyle magazines in October, the report said.
"We all want to find better ways to detect cancer early," Theron said. "I'm honored to join the Entertainment Industry Foundation's Women's Cancer Research Fund and Saks Fifth Avenue to help bring more attention to this cause and the importance of the cutting-edge scientific work being funded through Key to the Cure."
A percentage of sales from the Saks Fifth Avenue's shopping weekend beginning Oct. 14 will be donated to local and national breast and women's reproductive cancer research centers. In the past five years, Saks has raised over $13 million.