Freezing and storage of breast cancer tissue for estrogen receptor protein assay: a convenient method

Sixteen patients underwent biopsy of primary or metastatic breast cancer and had equal portions of the tumors rapidly frozen by either the use of liquid nitrogen or the fluorinated hydrocarbon spray, Cryokwik. The estrogen receptor protein (ERP) assay was then performed on both specimens, utilizing the surcose gradient density method. In general, both methods of freezing gave similar results. Three patients had ERP measured after approximately three to four months of storage at -70 C. After a minimum of 14 weeks' storage, there was no statistically significant loss of activity by either method of preparation. The Cryokwik preparation method makes the accurate measurement of ERP possible for all community hospitals. The tissue may be prepared and stored until a convenient time for transportation to the appropriate laboratory.