DALLAS - Packing a microscope and a yen for history, a Dallas pathologist has taken on one of the great medical mysteries of all time.

What killed Napoleon Bonaparte?

The French emperor, who fought and conquered most of Europe, was defeated by the British at Waterloo in 1815. He died six years later in exile on the South Atlantic island of St. Helena.

But the great warrior has continued to spark battles between those who say he died of natural causes and those who believe he was poisoned.

The latest to enter this arena is Robert Genta, a scholarly, soft-spoken professor of pathology at the University of Texas-Southwestern Medical Center at Dallas.

But solving the mystery wouldn't be easy.

"We had no evidence to look at. We only had the reports of others," said Genta, whose fellow investigators include five former colleagues, four Swiss and one Canadian.

Napoleon's autopsy indicated that he died of stomach cancer. But conspiracy theories that Napoleon had been poisoned arose from the start. They gained more credibility in the 1960s with the discovery of arsenic in samples of Napoleon's hair.

Napoleon was poisoned to prevent him from once again returning to power, conspiracy buffs say. They also argue that the emperor's reported obesity wasn't consistent with stomach cancer.

So Genta, a longtime expert on stomach cancer, decided to see for himself whether the autopsy's finding was correct. Would the conspiracy theorists finally meet their Waterloo in Dallas?

Genta and his team decided to conduct a case study using what he called a "kind of medical-legal approach." They applied modern clinical and pathological methods to historical reports.

The questions they would try to answer for a jury of skeptics: If Napoleon had escaped from St. Helena, could he have gone back to France and taken power for a third time? Or would his stomach cancer have quickly caught up with him, thwarting his final chance to change the history of the world?

So Genta's team went to work, comparing the findings in Napoleon's autopsy report with 50 modern cases of gastric cancer.

They determined that Napoleon had a large tumor extending the length of the stomach. That was a strong indication that his cancer had reached at least a stage-three level, Genta said.

At stage three, the prognosis is considered bleak, with a survival rate of less than 50 percent up to one year and less than 20 percent up to five years.

"We concluded that even if he had been seen by a cancer specialist today, he'd be dead in months," Genta said. That wouldn't have left much time for him to take over a village, let alone a continent.

Then there was the question of Napoleon's obesity. Genta's team looked at historical records and did extensive legwork. Swiss physician Alessandro Lugli and his wife, also a physician, visited museums around Europe, examining different pants that Napoleon had worn.

The pants investigation showed that the emperor had lost some of his girth over the years, Genta said.

All in all, the team determined that in the six months before his death, Napoleon's weight had dropped by as much as 33 pounds. Significant weight loss is common with stomach cancer.

In all likelihood, Napoleon had a Helicobacter pylori infection, a bacterial infection in the stomach that can lead to gastric cancer, Genta said.

His team's analysis of the autopsy report also showed an absence of medical signs that are consistent with arsenic poisoning, including lack of hemorrhage in the heart.

The team's report, which was published in the January edition of Nature Clinical Practice Gastroenterology & Hepatology, may not settle the debate, said Genta, who was senior author of the study.

"I'm sure the cynics will say this is not right," he said at his office at the Dallas Veterans Affairs Medical Center, where he spends part of his time. But if it increases awareness in gastric cancer, then all this attention to Napoleon's death might have a good result, he said.

Read the full case study via http://go.philly.com/napoleon.