Adam Yauch, 47, best known as MCA and a founding member of the Beastie Boys rap group, died Friday  after a three-year battle with salivary cancer, Rolling Stone magazine reports.

In 2009, Yauch received surgery and radiation therapy for what was then believed to be an early-stage cancer of the salivary gland. It's not yet clear whether his death was due to the cancer.

The cancer had spread from his parotid gland to a lymph node, but Yauch fully expected to be cured.

"It is a little setback, a pain in the ass, but it is treatable in most cases and people don't have continued problems with this," he said at the time in a video made for his fans.

But Dong Moon Shin, MD, a professor of otolaryngology, hematology, and oncology at Atlanta's Emory University, told WebMD at the time that it was impossible to predict a cure.

"Until the surgeon goes into the local area, we cannot assume any specific outcome," Shin said. He noted that predicting the course of Yauch's salivary cancer depended on the size and grade of the original tumor, the size of the tumor that spread to his lymph node, the extent of spread to the lymph node, and whether the cancer had spread to other parts of Yauch's body.

And it very much depended on the type of cell in the tumor, as salivary gland tumors may arise from many different cell types. Yauch had not publicly revealed these details.

Salivary Gland Cancer

Cancer of the salivary gland is a rare disease. It's considered a type of head and neck cancer.

There are three main pairs of salivary glands: the parotid glands in front of and below each ear, the sublingual glands under the tongue, and the submandibular glands below the jawbone.

In addition, there are hundreds of tiny salivary glands lining parts of the mouth, nose, and throat. Most salivary gland cancers begin in the roof of the mouth.

About half the time, salivary gland tumors are benign and do not spread.

According to the National Cancer Institute, signs of salivary gland cancer include:

• A lump (usually painless) in the area of the ear, cheek, jaw, lip, or inside the mouth
• Fluid draining from the ear
• Trouble swallowing or opening the mouth widely
• Numbness or weakness in the face
• Pain in the face that does not go away

SOURCES: Dong Moon Shin, MD, professor of otolaryngology, hematology, and oncology, Emory University, Atlanta, Ga. Rolling Stone: "Beastie Boys Co-Founder Adam Yauch Dead at 47."TMG web site. National Cancer Institute web site.

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