Automated immunohistochemical estrogen receptor in fixed embedded breast carcinomas. Comparison with manual immunohistochemistry on frozen tissues.

Estrogen receptor (ER) status of breast carcinomas determines prognosis and treatment. Biochemical ER assays are expensive and time-consuming and require fresh tumor. Immunohistochemical ER was assessed in 68 breast carcinomas, by an automated method using routinely processed formalin-fixed paraffin-embedded tissues, and manually with the use of snap-frozen tissues with a monoclonal anti-ER and peroxidase-antiperoxidase technique. The paraffin sections were digested with DNase to enhance development of signal. Positive nuclear ER was obtained in 9 (13%) fixed tissues and 36 (53%) frozen tissues. The sensitivity, specificity, and predictive value of a positive test result, as compared with the biochemical assay, were 25%, 100%, and 100% for the paraffin section technique, and 89%, 88%, and 89% for the frozen sections. Although it is specific, lack of sensitivity, resulting from loss of ER with fixation and room temperature handling, renders this immunohistochemical technique unacceptable on fixed tissues. However, ER immunostain on frozen tissue is an acceptable alternative to biochemical assay.