(1867–1928), Danish pathologist and Nobel laureate, known for his pioneering work in the etiology (causes) of cancer. Born in Silkeborg, he was educated at the University of Copenhagen, obtaining his Ph.D. in 1895. Fibiger was appointed professor of pathological anatomy at the University of Copenhagen and director of the Institute of Pathological Anatomy in 1900, where he spent the rest of his career.

Fibiger's early research was on the bacteriology of DIPHTHERIA, and TUBERCULOSIS, (qq.v.). In 1907, while examining rats infected with tuberculosis, he noted the incidence of stomach cancers among them. He also noted the presence in the center of these tumors of a parasite belonging to the family of Spiroptera. Attempts to provoke cancerous tumors by feeding the parasite to healthy mice failed. By 1913, however, he was able to induce such tumors in healthy mice and rats by feeding them cockroaches infected with the parasite. By showing how normal cells can be changed into cancerous cells, Fibiger demonstrated, for the first time, that cancer can be caused by an external stimulus. His findings gave impetus to the study of CANCER, (q.v.) and carcinogens (see CARCINOGEN,). His work led Japanese pathologists to conduct research with coal-tar induced tumors in rabbits, experiments which Fibiger himself adopted and used in the post–World War I period.

Fibiger was awarded the 1926 Nobel Prize in physiology or medicine for “his discovery of the Spiroptera carcinoma.”