Comparison of immunohistochemical and biochemical assay of steroid receptors in primary breast cancer--clinical associations and reasons for discrepancies.

Estrogen (ER) and progesterone receptor (PgR) status was analysed in paraffin-embedded breast cancer material with immunohistochemical (IHC) technique and compared with corresponding analyses in cytosols (CYT). ER showed the same status (positive/negative) with both methods in 88% of the samples (352/402). The concordance was also high for PgR status (81% [321/394]). Besides values near cut-off, heterogeneity in the distribution of receptor positive and negative nuclei within a tumour sample was the main reason for discordances. Histological type, presence of sclerosis, necrosis and non-invasive cells, and technical artefacts seem to be of only limited importance for explaining discordances All patients have been treated with adjuvant tamoxifen for two years. The two subgroups, which were ER(CYT)+/ ER(IHC) + or ER(CYT)-/ER(IHC) +, both had a significantly better progression-free survival (PFS; median follow-up: almost 6 years) than the ER(CYT)-/ER(IHC)- group (p < 0.001 and p = 0.007, respectively). The remaining group, ER(CYT)+/ER(IHC)-, had an intermediate PFS. For PgR, the associations with PFS were weaker, with significantly better PFS than the PgR(CYT)-/PgR(IHC)- group being found only for the PgR(CYT) +/PgR(IHC)- group (p = 0.03).