Brachylophosaurus
In 2003, evidence of tumors, including metastatic cancer, was discovered in fossilized Brachylophosaurus skeletons. Rothschild and co-workers tested dinosaur vertebrae for tumors using computerized tomography and fluoroscope screening. Several other hadrosaurs, including Edmontosaurus, Gilmoreosaurus, and Bactrosaurus, also tested positive. Although more than 10,000 fossils were examined in this manner, the tumors were limited to Brachylophosaurus and closely related genera. The reason for this is not known.