(CNN)A group of patients with a rare type of eye cancer called ocular melanoma has researchers and epidemiologists stumped.
The cancer, which normally occurs in about six in every 1 million individuals, has been identified in more than 50 individuals around two locations: Huntersville, North Carolina, and Auburn, Alabama. At least 38 of these individuals attended Auburn University between 1983 and 2001, according to a Facebook page for the group of patients.
At least four have died of the disease.
The exact cause of ocular melanoma is still unknown. Individuals at highest risk include those with light eye color, those with light skin color and those exposed to high levels of artificial UV radiation. People with certain occupations, such as cooks and metal workers, also appear to have an increased risk, according to a 2001 study.
No common cause has been identified in the current group of cases, Orloff says.
"We are not calling them official clusters. In order to meet the definition of a 'cluster,' you need to look at the expected incidence and observed incidence, and for a number of reasons it's been hard to qualify these as true clusters," Orloff said.
"But certainly, it's a unique accumulation of cases," she added.
The Alabama Department of Public Health indicates it is evaluating the recent increase in cases but says it has not identified a common source.
"We are working closely with Auburn, a survivor we have connected with and Dr. Orloff's team," said Justin George, director of cancer epidemiology at the Alabama Department of Public Health. "We are collaborating and working in an advisory role; the survivor who has spoken out is providing us a complete list of all those who have been sickened, and then we will work to verify the incidents and make sure the cases meet the definition of ocular melanoma."
Auburn said in a statement that it is "working closely with the Alabama Department of Public Health, which is leading the review of area cases of uveal melanoma. Researchers from the Sidney Kimmel Cancer Center and the coordinator of research in North Carolina have also been involved.
"While we have been informed by ADPH officials that it would be premature to determine that a cancer cluster exists in the area, we are cooperating fully with their work. The health and safety of our students, employees and alumni are of the utmost importance."
Allred believes the group of cases among former Auburn students is no coincidence. She and at least two other patients lived in neighboring sororities and were all education majors, she said.
Green and another patient "were in the same sorority, and my sorority dorm was right next to theirs. And we were all education majors," Allred said.
