Hearing that a horse has been diagnosed with cancer is one of many owners’ worst nightmares. But is there a way by which veterinarians can discover some cancers’ presence earlier, thereby allowing treatment to start sooner? Paraneoplastic manifestations of cancer–problems that are not due to the cancer’s physical presence, but to the cancer’s hormone secretion–are often the first clue a horse has developed the disease.

Philip J. Johnson, BVSc(Hons), MS, Dipl. ACVIM, Dipl. ECEIM, MRCVS, professor of internal medicine at the University of Missouri’s College of Veterinary Medicine, discussed paraneoplastic conditions at the 2011 American Veterinary Medical Association Convention, held July 16-19 in St. Louis, Mo.

"Sometimes the paraneoplastic manifestation is the most important and earliest sign of cancer," he explained. "For example, we often see an older horse that is weak, inappetant, and losing weight as a result of the cancer, but there is no sign of that cancer on physical examination.

"So the veterinarian might run routine blood work and notice an elevated blood calcium concentration. This abnormality, called hypercalcemia, has several possible causes, one of which is a paraneoplastic manifestation of underlying cancer