Long-term follow-up post-cryosurgery in a sheep breast model

This study constitutes the advanced stage of an ongoing project for the dev elopment of cryosurgical devices and techniques for breast cryosurgery. The current study focuses on the long-term follow-up post-cryosurgery in a she ep breast model. Results of this study indicate that the cryotreatment site in a sheep breast model cannot be identified up to 5 months post-cryosurge ry by means of ultrasound, mammography, or MRI. Histology findings of this study further indicate that there is no gross or microscopic difference bet ween lesions that have been subject to one versus three freeze/thaw cycles. Under either cryosurgical protocol, there is a main cryoinjured region tha t has uniform destruction of epithelium and healing scar formation and a tr ansition zone of damaged lobules without acini, surrounded by healthy tissu es. The cryoinjured region at 5 months post-cryosurgery was found to be abo ut half the diameter of the ultrasound-imaged frozen region during the cryo procedure. This study shows that, in terms of recovery and regeneration, su rgical excision appears to have an advantage over cryosurgery, which result s in a more rapid healing process. Based on observations that the cryoinjur ed region is no smaller than the ultrasound-imaged ice-ball and that the ty pical thickness of the transition zone is up to 5 mm, a conservative use of the cryosurgical device developed for the current study in an ultrasound-m onitored cryoprocedure requires at least 5 mm safety margins of the frozen region radius around the target region. (C) 1999 Academic Press.