Cancer in ancient times would appear to be linked to genetics, since the environment then was free of industrial pollutants. (National Museum of Archeology/Associated Press)

An Egyptian professor says the discovery of prostate cancer in a 2,200-year-old mummy indicates the disease was caused by genetics, not environment.

The genetics versus environment question is key to understanding cancer.

American University in Cairo professor Salima Ikram, a member of the team that studied the mummy in Portugal for two years, said Sunday the mummy was of a man who died in his 40s.

"These radiologic findings in a wrapped mummy, to the best of our knowledge, have never previously been documented, and could be one of the oldest evidence of this disease, as well as being the cause of death," Ikram and her co-authors concluded in the International Journal of Paleopathology.

Ikram said this was the second-oldest known case of prostate cancer.

"Living conditions in ancient times were very different; there were no pollutants or modified foods, which leads us to believe that the disease is not necessarily only linked to industrial factors," she said.

A statement from AUC says the oldest known case came from a 2,700-year-old skeleton of a king in Russia.