Here are three good articles which explain that the Microchip can give you or your pet cancer

...Foreign body induced tumors can pose serious threats to animal health. Researchers report that most tumors arising from foreign bodies are malignant mesenchymal neoplasms with a rapid growth rate, killing the animal in a matter of weeks. Many of the study animals with microchip associated tumors died prematurely....

..The Toxicology Department of Bayer Corporation in Stillwell, Kansas reported, “Tumors surrounding implanted microchip animal identification devices were noted in two separate chronic toxicity/oncogenicity studies using F344 rats...

...neither the company nor the regulators publicly mentioned this: A series of veterinary and toxicology studies, dating to the mid-1990s, stated that chip implants had “induced” malignant tumors in some lab mice and rats. “The transponders were the cause of the tumors,” said Keith Johnson, a retired toxicologic pathologist, explaining in a phone interview the findings of a 1996 study he led at the Dow Chemical Co. in Midland, Mich...