Shamsuddin said the tumor could be a sarcoma - a malignant tumor of the bone or soft tissue - or a cancer that spread from an organ to her tailbone, but there is no evidence of cancer elsewhere in Troia's body. He said it's more likely bone cancer.
The Armed Forces Institute of Pathology reviewed a biopsy and described it as an aggressive cancer, but the institute also couldn't determine the tumor's origin, Shamsuddin said.
Such cases are extremely rare, Shamsuddin said.
According to the American Cancer Society, cancers that start in bone, muscle or fibrous tissue can develop anywhere in the body and account for less than 0.2 percent of all cancers.
While cancer researchers now know more about cancer than they ever have, there is still significant work to be done to understand what causes different types of cancer, how to prevent cancer and how to improve the quality of life for those affected by cancer, American Cancer Society spokeswoman Dawn Ward wrote in an e-mail to The Herald-Mail.
The society has spent about $3 billion in cancer research since it began its research program in 1946, Ward said. Currently the society is paying for more than $10.4 million in cancer research conducted at Maryland research institutions and hospitals, and more than $431 million nationwide.
While Troia appreciates the investment in cancer research, she said it's of little comfort to her because medical officials still don't know what's going on with her cancer.
On March 27, Troia completed her radiation treatments, about 25, designed to give the tumor as much radiation as possible but sparing as much regular tissue as possible.
She said she is in the midst of a respite from chemotherapy treatments and will continue those in a few weeks.
She expects to get magnetic resonance images of the tumor within the next several weeks to see if the tumor has shrunk from what was the size of a softball.
If it hasn't, Troia might have to consider a surgical option she hasn't wanted to think about - amputation of her right leg and part of her buttocks.
Because Troia's cancer has not appeared anywhere else in her body, it's possible the tumor on her tailbone is the primary location, Shamsuddin said.
The other thing Troia doesn't know is how she got the cancer. She has never smoked and can't think of any habits or circumstances that would have led to her condition.
The first sign of a problem was in March 2006 when she experienced pain in her right leg. The pain went away, returning in mid-October 2006. Troia said she thought she had pulled a muscle, but when the pain didn't subside after two weeks she sought medical attention.
Shamsuddin said Troia's situation is unusual, but there are proven ways to detect several types of cancer, hopefully early enough for treatment. Those include mammograms, colonoscopies, blood screenings for prostate cancer and pap smears for cervical cancer.
Early detection and screening methods have improved greatly during the last 50 years, including recent advancements in vaccinations for cervical and prostate cancers, Ward said.
Troia said she's gotten mammograms and pap smears, but they didn't help discover this particular kind of cancer.
Meanwhile even though Troia is taking numerous painkillers she said she still feels pain from the tumor when she moves.
Shamsuddin said the pain is so severe because the large tumor is along her spine and a bundle of nerves.
Troia's husband, Denny, is a self-employed contractor who said his insurance covers visits to doctors and hospitals and 60 percent of the medication. But the many medications his wife takes, including several painkillers, are expensive, plus there are travel and motel expenses every time she has to visit Hershey Medical Center in Hershey, Pa., for testing.
In March alone, Denny Troia said the couple's share of his wife's medication was at least $1,585.
He also had to cut back on his work hours to spend more time at home to care for his wife.
"I'm a proud man," Troia said. But, he said, they need help. The couple is one month behind on their mortgage because Denny Troia said he had to make a decision whether to pay the mortgage or medical expenses. He is increasing his work hours the next few weeks to help pay the overdue mortgage.
The Troias established a nonprofit account in March at First National Bank of Greencastle for people who want to make donations to help with Linda Troia's medical expenses.
Denny Troia said so far the couple has received at least $3,000 in donations.
They're grateful for the help, though Denny Troia said he doesn't feel good about accepting others' money.
Donations can be made at any First National Bank of Greencastle branch or by mailing a check, made payable to Linda Troia Medical Fund, to First National Bank of Greencastle, P.O. Box 8, Greencastle, PA, 17225.