The incidence of spontaneous neoplasia in two populations of captive rhesus macaques (Macaca mulatta).

Rhesus macaques (Macaca mulatta) are genetically similar to humans and share many characteristics of aging and age-related diseases. They age at approximately three times the rate of humans and develop spontaneous cancers. In both humans and rhesus macaques, cancer incidence increases with age with the greatest incidence in those over 60 years of age and 20 years, respectively. The current survey reports on the incidence of spontaneous neoplasia in two colonies of captive rhesus macaques: the Wisconsin National Primate Research Center colony with 28 years of records and a National Institute on Aging colony with 21 years of records. When categorized by organ and histologic diagnosis, the average age at diagnosis was greater than 20 years for all categories except oral squamous cell carcinoma. Neoplasms of the gastrointestinal system were the most commonly diagnosed, accounting for 48.8% of the cases. Adenocarcinomas of the large intestine were the most prevalent tumor identified. Although there are differences in the biological behavior of cancer in the rhesus macaque when compared with humans, they are a valuable model of comparative oncology.