Sharon Osbourne is facing a setback in her battle against colon cancer.

The lively, tough matriarch of MTV's The Osbournes has revealed in an interview with People that her cancer has spread and that she will undergo three months of chemotherapy to contain it.

"It was not the best news," Osbourne, the spouse and manager of metal pioneer-turned-TV dad Ozzy Osbourne, says in the magazine's July 29 edition. "You think nothing will ever happen to you. You're invincible. Then after you get over the shock and panic, you realize how lucky you are to be alive."

After Ozzy, an admitted hypochondriac, insisted she go in for her first checkup in three years, the 50-year-old Sharon Osbourne was diagnosed with colorectal cancer on July 1. Two days later she went under the knife at a Los Angeles-area hospital, where doctors removed a one-foot section of her colon.

Just days later, Osbourne's publicist issued a statement saying, "Doctors expect her to make a full recovery."

But her illness turned out to be more serious than either she or her physicians first thought. A lymph node removed during the operation tested positive for cancer cells, indicating the disease had spread beyond the bowel wall.

Her chemotherapy begins July 29.

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> Known on The Osbournes as a sort of anti-June Cleaver for lording over a house that includes her space cadet hubby, their rebellious teen kids, aspiring music executive Jack and burgeoning pop star Kelly (older daughter Aimee was MIA in the first season), and a menagerie of weak-bladdered pets, Sharon handled the bad news with typical aplomb.

"Why'd they have to find it in my bum of all places?" she jokes.

Osbourne says she remains upbeat and that her prognosis is still "very, very good."

She says her cancer treatment, which will be documented on the upcoming second season of The Osbournes, will be handled with humor.

"We need to get a different vibe going," she says of the cancer treatment center. "I think I'll bring some music, introduce myself, maybe we can sing some songs and cheer the place up...People will see me having chemo. It'll be interesting."

Sharon is so confident that she will recover that, according to the New York Daily News, she is considering parlaying her image as an influential TV mom into having her own daytime talk show. Osbourne is said to be in talks with syndicator King World, the folks behind Oprah and Jeopardy, about possibly hosting such a program. She's also considering penning a book on parenting, Osbourne-style of course.

Not faring nearly as well over the cancer news is Ozzy, who Sharon says in People, was a complete wreck and "was hysterical, just terrified." Sharon says her husband was so distraught that a doctor was called to the house to sedate the usually out-of-it Ozzy.

The rocker, who called himself the "Prince of f---ing Darkness" on one memorable episode, has said he has since looked heavenward for some divine intervention, praying for his wife's recovery.

"She's my whole world," he tells People. "She's the best lover I've ever had, the best friend I've ever had. She has been my pillar of strength for many years."

Meanwhile, Sharon isn't the only Osbourne member requiring some quality time at the hospital.

In a bit of daredevilry gone awry, 16-year-old Jack reportedly injured his left arm while trying to scale a vacant two-story building on the Malibu Pier.

He was in the company of a group of friends, who were apparently climbing the vacant buildings and diving into the ocean.

"I looked up and there was a bunch of kids doing cannonballs off the Malibu Pier, which is illegal," Norton Wisdom, a Los Angeles County lifeguard who patrols the Beach, tells the Associated Press.

Jack lost his grip, however, and plunged to the pier deck.

Lifeguards who witnessed the fall said Jack was in a state of shock following his hard landing, but suffered only minor injuries. They immobilized his left arm, after he complained of a sharp pain.

A film crew that was following Jack around at the time of the accident (authorities say they were shooting without a permit) took him to nearby St. John's Malibu-Urgent Care center where he was treated and released.

No word on whether they were filming for The Osbournes, which just earned an Emmy nomination. The new season is set to kick off this fall.