Cancer is a disease of antiquity. The Ancient Greeks were familiar with onkos (from which we have the term oncology)—tumour of all sorts. Hippocrates coined karkinos and karkinoma, our source of the words cancer and carcinoma. Of a plethora of carcinogens, parasitic worms (helminths) constitute a considerable health concern. Three trematodes, Clonorchis sinensis, Opisthorchis viverrini, and Schistosoma haematobium are now officially classified carcinogens. But the discovery of helminths as cancer-causing agents took wrong turns and marks an inglorious chapter in the history of science. The carcinogenicity of worms, vindicating Rudolf Virchow’s reiztheorie (irritation theory) of cancer origin, was glorified in the scientific forefront by Johannes Fibiger in the 1910s. Discovery of a new nematode, which he proudly named Spiroptera carcinoma, and his subsequent demonstration that the parasite could induce stomach cancer in rats, earned Fibiger a retrospective Nobel Prize in Physiology or Medicine in 1926, and a lasting fame. But not in an appealing way. His achievement did not withstand the test of time. S. carcinoma was annulled as an invalid taxon in zoology—supplanted by Gongylonema neoplasticum—and eventually was branded as a non-carcinogenic agent.