Multiple microsample analysis of intratumor estrogen receptor distribution in breast cancers by a combined biochemical/immunohistochemical method.

A multiple microsample analysis of estrogen receptors (ER) was performed on 81 samples obtained from 21 human breast cancers using a biochemical (BC) and immunohistochemical (IHC) method. Qualitative agreement occurred in 96% of the cases. Using both the percentage of cells staining specifically for ER as well as the intensity of staining (Histoscore) a semiquantitative correlation between the two analyses was obtained. Large variations in cellularity and the percentage of cells that stained specifically for ER existed within individual tumors. In most cases the variation in intensity of staining was minimal. Both the level and distribution of ER in different areas of individual tumors were calculated using a correction for differences in cellularity amongst samples. Heterogeneity in ER level as well as distribution was found in some tumors. In addition, a "checkerboard" type of staining with intermixed ER positive and ER negative cells was observed. This combined BC/IHC method may provide specific information about intratumor ER heterogeneity not available from either method alone.