Gongylonema neoplasticum is a species of nematode. It was previously known as Spiroptera carcinoma. Under this name, it was the basis of the research that won Johannes Fibiger the 1926 Nobel Prize in Physiology or Medicine. His research indicated that nematode infection led reliably to gastric tumors in rats, and this finding was one of the first demonstrations that an infection could be a carcinogen. His work was later reappraised, and current consensus is that while the worms stimulated previously damaged cells to form tumors, the worms themselves were not carcinogenic to healthy cells.