SUBCUTANEOUS SOFT-TISSUE TUMORS AT THE SITE OF IMPLANTED MICROCHIPS IN MICE

An experiment using 4279 CBA/J mice of two generations was carried out to investigate the influence of parental preconceptual exposure to X- ray radiation or to chemical carcinogens. Microchips were implanted su bcutaneously in the dorsolateral back for unique identification of eac h animal. The animals were kept for lifespan under standard laboratory conditions. In 36 mice a circumscribed neoplasm occurred in the area of the implanted microchip. Females were significantly more frequently affected than male mice. An influence of age or different treatment o n the s. c. tumour incidence in two mice generations could not be obse rved. Macroscopically, firm, pale white nodules up to 25 mm in diamete r with the microchip in its center were found. Microscopically, soft t issue tumours such as fibrosarcoma and malignant fibrous histiocytoma were detected.