Dr. Oz explains how a tumor grows.

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To understand what happened to Linda, Dr. Oz explains what a tumor actually is, using a replica of Linda's tumor.

It starts with individual cells. "But cancer cells are sociopathic—they don't get along with each other," he says. "They have sharp elbows pushing the other cells out of the way."

Those cancerous cells really become a threat if they tap into a supply of blood vessels, Dr. Oz says. "They bring nutrients that allow the cancer to grow, and they give the cancer a way to escape, because the cancer gets into the blood cells," he says. "They get into the lymph nodes, and that's how cancer will spread."
Another big mystery is how the tumor could have gotten so massive without anyone ever knowing.

"It's a two-way street," Dr. Oz says. "When you miss a 140-pound tumor, a couple things happened wrong. The first was you were pretty heavy. You were over 300 pounds. When you're over 300 pounds, it's hard for doctors to get to your stomach. ... It's difficult to tell what's normal or not. You were too big to get into the scanner. They couldn't get pictures that they normally would take of the inside."
As a reminder, always consult your doctor for medical advice and treatment before starting any program.