Parker's story, which has received national attention, began without much fanfare with a small growth noticed last October on the floor of his mouth. According to the Jensens, Parker's dentist said it was a clogged saliva duct. When it hadn't disappeared after six months, the dentist referred them to an oral surgeon, who removed the nodule and sent it to the Laboratory Corporation of America in Kent, Wash.

After reviewing the lab work, Dr. Cheryl Coffin, chief of pathology at Primary Children's, confirmed that the tumor was Ewing's sarcoma, an aggressive cancer generally found in the bone but occasionally in soft tissue.

The Jensens have claimed that the second opinion they sought from Los Angeles Children's Hospital about Parker's diagnosis was simply a "rubber stamp" of Primary Children's original diagnosis. They also claim that subsequent tests conducted on Parker were "negative" and that Primary Children's is only assuming that their son has cancer, based on "micrometastatic cancer" that can't actually be tested for. Parker, they point out, looks and feels healthy — and seems so in recent photographs that show him riding a motorbike and jumping on a trampoline with his siblings and cousins.

Chemotherapy, they argue, is too toxic to be prescribed for a child who might not really have cancer.

Doctors have a different take. Although physicians associated with the case won't talk on or off the record, a Guardian Ad Litem report issued last week said three laboratories had tested tissue sample, and each had confirmed the Ewing's sarcoma diagnosis.

"If it's been looked at by two different labs, I'd be pretty comfortable with the diagnosis," said Dr. William H. Meyer, a pediatric oncologist at the University of Oklahoma Health Sciences Center.

Whenever Ewing's is diagnosed, said Meyer, chemo is the required response.

Yes, Parker may look healthy. Yes, micrometastatic cancer cells are impossible to test for. But years of caring for children with Ewing's — most patients are between 4 and 20 years old — have shown that chemotherapy is the only thing that works, said Dr. Joe Simone, a pediatric oncologist who was former clinical director at the Huntsman Cancer Institute and now runs a private consulting service in Atlanta.

Micrometastatic cancer, he said, is like a barrel of water into which you've dropped a tiny blob of oil. "Over time, the droplets will disperse. Little tiny bits of it mix with the water, and you can't see it with the naked eye." With Ewing's, the cancer may show up as a tumor, but tiny cancerous cells may also have infiltrated between normal cells.

For years, surgeons simply removed the Ewing's tumor. "They would go in and say, 'I got it,' and the kid always died," said Simone. So doctors began adding localized radiation. "But the recurrences still happened at about the same rate." In the early 1970s, doctors began trying chemotherapy after surgery.