Now, scientists say they have, for the first time, found that dinosaurs suffered from osteosarcoma -- an aggressive malignant cancer that afflicts humans today.
When a lower leg bone or fibula from a horned dinosaur called Centrosaurus apertus that lived 76 to 77 million years ago was unearthed in Dinosaur Provincial Park in Alberta, Canada, in 1989, the malformed end of the fossilized bone was originally thought to be a healing fracture.
But a more detailed analysis, using modern medical techniques that approached the fossil in the same way as a diagnosis in a human patient, revealed that it was osteosarcoma, a bone cancer that in humans today usually occurs in the second or third decade of life.
It's an overgrowth of disorganized bone that spreads rapidly both through the bone and to other organs, including most commonly, the lung.
"Diagnosis of aggressive cancer like this in dinosaurs has been elusive and requires medical expertise and multiple levels of analysis to properly identify," said Dr. Mark Crowther, a professor of pathology and molecular medicine at McMaster University in a press statement.
"Here, we show the unmistakable signature of advanced bone cancer in (a) 76-million-year-old horned dinosaur -- the first of its kind. It's very exciting," said Crowther, author of the paper, which published Monday in the journal Lancet Oncology.
The team analyzing the fossilized bone included professionals from diverse fields including pathology, radiology, orthopedic surgery and paleopathology -- the study of disease and infection in the fossil record.
The bone was examined, cast and CT scanned before a thin slice of the bone was studied under the microscope. Then, powerful three-dimensional reconstruction tools were used to visualize the progression of the cancer through the bone. The investigators ultimately reached a diagnosis of osteosarcoma.
To confirm their diagnosis, the team compared the fossil to a normal fibula from a dinosaur of the same species, as well as to a fibula belonging to a 19-year-old man with a confirmed case of osteosarcoma.
Osteosarcoma is the cancer that afflicted Canadian athlete Terry Fox, a national hero who in 1980 set out to cross Canada, running about the equivalent of a marathon each day to raise money for cancer research. But Fox, who had a prosthetic right leg, had to quit after 143 days as his cancer spread. He died less than a year later.
Common biological links
"It is both fascinating and inspiring to see a similar multidisciplinary effort that we use in diagnosing and treating osteosarcoma in our patients leading to the first diagnosis of osteosarcoma in a dinosaur," said Seper Ekhtiari, an orthopedic surgery resident at McMaster University and study co-author.
The fossil specimen is from an adult dinosaur with an advanced stage of cancer that may have invaded other body systems; however, it's not clear if the dinosaur was killed by the cancer.
It was found in a massive bone bed, suggesting it died as part of a large herd of Centrosaurus that was struck down by a flood.
"The shin bone shows aggressive cancer at an advanced stage. The cancer would have had crippling effects on the individual and made it very vulnerable to the formidable tyrannosaur predators of the time," said study-co author David Evans, the James and Louise Temerty endowed chair of vertebrate palaeontology at the Royal Ontario Museum in Toronto in the news release.
"The fact that this plant-eating dinosaur lived in a large, protective herd may have allowed it to survive longer than it normally would have with such a devastating disease."
This study said it aimed to establish a new standard for the diagnosis of diseases in dinosaur fossils and opened the door to more precise diagnoses.
Studying disease in fossils is a complicated task given there are no living references. The diseases of the past, however, will help scientists to gain a better understanding of the evolution and genetics of disease, experts say.