Maybe there was something on the ground when Mark "Pete" Peterson waded through rice paddies in Vietnam in his first year as a U.S. Marine. Or in the air, across Asia and South America, where he piloted helicopters for most of his 22 years of service.
Or maybe there was nothing and he got sick for no apparent reason.
It began as a sore throat, like the ones before a seasonal head cold. It was mid-August 2012.
"After a week, the runny nose and mucus buildup never showed up," recalls the West Grove resident, who is 65. He went to see his family practitioner, who prescribed a 10-day course of antibiotics. No effect.
Now almost three weeks in, Peterson turned to an ear, nose, and throat doctor in West Chester who scoped and biopsied the still-painful throat.
"Gee whiz, I have no idea," the patient recalls hearing the bewildered specialist say as he snipped a piece of gray tissue near the vocal cords.
Looked like cancer but wasn't recognizable. Results took a week and were inconclusive. Nearly a month and a half had passed, and Peterson's scratchy throat remained. "My wife became very worried and put out the word we were in search of a specialist at Penn," he says.
They found one in Ara Chalian, a head and neck surgeon at the Hospital of the University of Pennsylvania. Peterson waited two weeks for an appointment, taking him into October.
Another scope, but one that enabled Peterson to see the probe's feedback on a video screen along with Chalian. "I saw a mostly pink collar the shape of a lifesaver around my windpipe, then a dull gray area on the right side," Peterson says.
A more extensive biopsy was taken and the results came back 10 days later with a confirmed diagnosis that had Chalian and his team at Penn scratching their heads.
"This did not have the typical appearance of a throat cancer," he said.
Two months in and the reason he still had a sore throat finally had a name:
NK/T-cell lymphoma. But it was still a mystery. The cancer was in an unusual place: under the voice box.
NK (natural killer cells) in combination with T-cells is a rare and aggressive non-Hodgkin's lymphoma. It is an extranodal lymphoma, lethal to organs and tissues other than lymph nodes, that destroys cartilage, bone, and soft tissue. It's hard to diagnose because biopsy space is often scant.
Not much is known about it because it makes up just 1.5 percent of lymphomas in North America.
NK/T-cell lymphoma is one Chalian and colleagues had seen only a few times in their careers.
More prevalent throat and nasal cancers are called lethal midline granulomas, which are aggressive enough to cave in the face or nose. But Peterson's tumor didn't have granuloma markers.
Instead, markers were found for a lymphoma linked to a strain of the Epstein-Barr virus (EBV) endemic in Asia and South America.
EBV lives unnoticed in more than 90 percent of the world's population. Only a fraction develop into diseases. The most common are infectious mononucleosis prevalent in Europe and North America, Burkitt's lymphoma in Central Africa, and nasopharyngeal cancer, including NK/T cell lymphoma, common in South America and Southeast Asia, Peterson's "office" for 15 years.
"It is believable that while in those areas, he was exposed to a strain of EBV that is a clear link to this diagnosis," says John Plastaras, a radiation oncologist at Penn.
Plastaras also found the tumor's location odd because NK/T-cell lymphoma typically occurs in the nose and throat.
"What is this thing, and why is it in this unusual location?" Plastaras recalls thinking.
Doctors began an investigation. Research from Samsung University in South Korea proved key.
NK cells are lymphocytes, like B-cells and T-cells. When NK cells become cancerous, they are generally grouped with other T-cell lymphomas, some of which are quite rare, and, as in Peterson's case, hard to diagnose. They are also challenging to treat. Basic lymphomas respond to modest doses of radiation.
Higher doses would be needed for this type of radiation-resistant lymphoma, according to trial data from the Samsung study.
Plastaras said a pre-radiation PET scan found another problem: a tiny node near the tumor. Rather than be lulled by its size, doctors opted to treat it as a threat.
"The clinical trials in Asia gave us a hint as to what to do - add chemotherapy," said Plastaras, who worked with Jakub Svoboda of hematology-oncology.
Peterson was about to see the lifesaving power of nuclear medicine - years after his role as a presidential military aide guarding the launch codes for nuclear weapons.
Peterson "carried the football" for President Ronald Reagan as part of a team who kept a briefcase, also known as the football, attached to themselves and accessible to the president at all times.
His treatment began the Monday after Thanksgiving, nearly four months after his throat became scratchy. Chemotherapy began at the end of January and ended in mid-February.
Follow-up PET scans in May 2013 and April 2014 showed no sign of cancer.
No mystery how that happened.