This is an AP story about studies that were published in veterinary and toxicology journals between 1996 and 2006. Between 1% and slightly more than 10% of mice and rats implanted with microchips developed subcutaneous sarcomas, malignant tumors, with most of them encasing the implants. It's important to note the lack of controls in any of the studies.It is unclear if the FDA reviewed these studies before its approval of RFID technology.
I don't want to suggest that it is possible to assume these results can be applied to the risk to humans.
VeriChip Chairman and CEO:
The company was "not aware of any studies that have resulted in malignant tumors in laboratory rats, mice and certainly not dogs or cats," but he added that millions of domestic pets have been implanted with microchips, without reports of significant problems.
He goes on to say:
"In fact, for more than 15 years we have used our encapsulated glass transponders with FDA approved anti-migration caps and received no complaints regarding malignant tumors caused by our product."
UPDATE: I see this story has been Slashdotted with the title "Implanted RFID Chips Linked to Cancer." I prefer that title I used for this post, but I sure the MSM will come up with even more dramatic headlines to help inflate interest. I didn't link to the Slashdot post, mainly because the comments are pretty sophomoric.