Officials say Tony Grier suffered from a rare lung disease. Back in January 2005, he joined a transplant waiting list and received the lungs.
Although doctors noticed a spot on his lungs a month later, the lawsuit claims they did not diagnose the cancer until late May.
The 43-year-old New Jersey man remained hospitalized at Penn from then until his death on July 16th.
The suit filed by Grier's mother alleges that Penn told Grier he was getting the healthy lungs of an 18-year-old -- a charge that Penn denies.