In 2009, Yauch had been treated for a cancerous parotid gland and a lymph node, undergoing surgery and radiation therapy. At the time, Yauch expressed hope it was "very treatable," but his illness caused the group to cancel shows and delayed the release of their 2011 album, "Hot Sauce Committee, Pt. 2."
The Beastie Boys - a trio of white Jewish kids - established themselves as one of the most respected groups in hip-hop at a time when white rappers were few.
Yauch, along with Adam "Adrock" Horovitz and Michael "Mike D" Diamond, founded the Beastie Boys in 1979. They released their chart-topping debut "Licensed to Ill" in 1986, a raucous album led by the anthem "(You Gotta) Fight for Your Right (To Party!)". The album was the first hip-hop album to top the Billboard 200.
The Beastie Boys were from the East Coast, but they recorded one of their albums in a studio in Atwater Village.
The group won three Grammys and was inducted into the Rock and Roll Hall of Fame this year. Yauch did not attend the ceremony due to illness, but Horovitz and Diamond read an emotional note from Yauch that ended with him calling his wife and daughter his soulmates.
When introducing the group at the Rock Hall, Public Enemy rapper Chuck D said the Beastie Boys "broke the mold."
"The Beastie Boys are indeed three bad brothers who made history," said Chuck D. "They brought a whole new look to rap and hip-hop. They proved that rap could come from any street - not just a few."
Celebrities reacted to the new of Yauch's death. Russell Simmons posted on his website Global Grind, "Adam was incredibly sweet and the most sensitive artist, who I loved dearly. I was always inspired by his work. He will be missed by all of us."
Musician Benji Madden tweeted, "This news hits hard. The Beastie Boys are 1of the reasons I do music & MCA was the captain. Thanx for everythin MCA. Rest in Peace."
The Brooklyn-born musician was also an activist and helped create the nonprofit Milarepa Foundation, which produces the Tibetan Freedom Concert benefits.
Yauch is survived by his wife, Dechen Wangdu, and daughter, Tenzin Losel.
The Associated Press contributed to this report.