Johnson, K., 1996: "Foreign-body tumorigenesis: Sarcomas induced in mice by subcutaneously implanted transponders." Toxicologic Pathology. 1996; 33(5):619. Abstract #198.

Summary: A two-year Dow Chemical study of 2,000 mice found an approximately 1% incidence of sarcomas surrounding microchip implants used for identification purposes. The tumors appeared in both control and experimental animals. This was consistent with a diagnosis of foreign-body-induced sarcoma.

Excerpt: "Investigators using. . . implanted devices need to be aware of foreign-body tumorigenesis [cancer development] when evaluating the results of long term studies using mice."