In conclusion, some of the injection-site associated sarcomas seen in cats (and occasionally in dogs), as well as the microchip associated sarcomas, may be examples of foreign body tumours associated with foreign material, probably insoluble aluminium compounds (or microchips) which results in inflammation, failure of resolution, chronic inflammation, and subsequent DNA damage and cell proliferation, with the induction of p53 as a counter measure to suppress the process of carcinogenesis through disruption of the cell cycle and initiation of apoptosis. The gene discussed is TP53; the disease is neoplasm.