Progesterone receptor detection in paraffin sections of human breast cancers by an immunoperoxidase technique incorporating microwave heating.

We sought to establish an easily interpretable and highly sensitive immunohistochemical method for detecting progesterone receptor protein in formalin-fixed, paraffin-embedded samples of breast carcinomas. Beginning with a conventional immunoperoxidase staining procedure, we incorporated microwave heating to compensate for the effects of conventional fixation and processing and then applied the method to 90 samples of primary breast carcinomas. We used the results of hormone binding assays as true values to establish the sensitivity, specificity, positive predictive value, and negative predictive value of the staining method. Our technique yielded good preservation of morphological detail and low nonspecific staining of background tissue. Comparisons of the results of staining and biochemical assays revealed that this progesterone receptor immunostaining procedure shows high sensitivity and acceptable specificity. We believe its performance characteristics make reliable study of small specimens and archival material possible.