Johannes Andreas Grib Fibiger (23 April 1867 – 30 January 1928) was a Danish physician and professor of anatomical pathology at the University of Copenhagen.

He was the recipient of the 1926 Nobel Prize in Physiology or Medicine "for his discovery of the Spiroptera carcinoma".

While working at the Institute of Pathological Anatomy of University of Copenhagen, Fibiger discovered new roundworms in 1907 from wild rats.

[1] In 1926, he was nominated for the Nobel Prize in Physiology or Medicine along with Katsusaburo Yamagiwa, who had experimentally induced carcinoma by painting crude coal tar on the inner surface of rabbits' ears in 1915.

Erling Norrby, who had served as the Permanent Secretary of the Royal Swedish Academy of Sciences and Professor and Chairman of Virology at the Karolinska Institute, in 2010 declared Fibiger's Nobel Prize as "one of the biggest blunders made by the Karolinska Institute.

[4] His father died of internal bleeding when he was three years of age, after which the family moved to Copenhagen where his mother earned their living by writing.

In 1883, at age 16, he passed his matriculation and was enrolled at the University of Copenhagen to study zoology and botany.

For a few months he worked as a physician at different hospitals, and also continued to study under Robert Koch and Emil Adolf von Behring in Berlin.

One of his experiments from 1898 in which he tested the blood serum for diphtheria is regarded by some as the first controlled clinical trial.

[3] While working as a Junior Physician in Blegdamshospitalet, he tested his diphtheria serum among hundreds (484) patients.

According to an article in The British Medical Journal in 1998: [Fibiger's experiment in 1898] was the first clinical trial in which random allocation was used and emphasised as a pivotal methodological principle.

He published his discovery in a series of three papers, and also presented them at the Académie Royale des Sciences et des Lettres de Danemark (Royal Danish Academy of Sciences and Letters), and Troisième Conférence Internationale pour l’Étude du Cancer (Third International Conference for Researches in Cancer) at Brussels the same year.

With Hjalmar Ditlevsen, of the Zoological Museum of the University of Copenhagen, he described it as Spiroptera (Gongylonema) neoplastica in 1914.

[8] Ditlevsen revised the description in 1918, and gave the final valid name Gongylonema neoplasticum.

His discovery was supported by the experiment of two Japanese scientists Katsusaburo Yamagiwa and Koichi Ichikawa in 1918.

[11] A number independent experiments subsequently confirmed the cancer-inducing effect of coal-tar in mice.

Henschen was in favour of the nomination and concluded that "the experimental carcinoma is worthy of the Nobel Prize.

But Bergstrand opposed to it, concluding that "an experimental confirmation of a previously known fact... [referring to the prevalence of cancer among chimney sweeps and factory workers, an already established medical fact at the time[16][17]] can, in this case, not be considered... that one cannot, at this point, find much support for the possibility that the work of Fibiger and Yamagiwa will have great importance in the solving of the riddle of cancer.

However, the authority at the Karolinska Institute disagreed with the recommendation for Warburg for undisclosed reasons, and Fibiger became the sole winner.

They concluded that Fibiger had probably mistaken metaplasia (a non-cancerous tumour) with malignant neoplasia (true cancer).

[28] Although G. neoplasticum is non-carcinogenic, other helminth parasites such as Schistosoma haematobium, Opisthorchis viverrini and Clonorchis sinensis are now established to cause cancer in humans.