Estrogen receptor immunocytochemistry: the promise and the perils

Estrogen receptor immunocytochemistry (ERICA) is favored over dextran-coated charcoal (DCC) or sucrose gradient assay (SGA) by many pathologists and oncologists since it allows an estimation of tumor cell and tissue heterogeneity and permits assays to be performed on specimens not suitable for DCC/SGA. Additionally, ERICA can be performed with greater ease and with less expense at the level of the community hospital pathology laboratory. Initially, like DCC/SGA, ERICA had to be done on fresh or frozen tumor samples or face a significant loss in sensitivity when applied to formalin-fixed, paraffin-embedded sections. Recently, several anti-estrogen receptor (ER) antibodies have appeared which can be successfully employed to assay routinely prepared tissue sections if used in conjunction with new antigen-retrieval techniques such as the microwave oven and citrate buffers. However, more work is needed to correlate results of these new procedures with biochemical ER assays, endocrine response, and survival before they can be reliably employed as prognostic parameters. Furthermore, if any ER assay is to be useful and valid, strict attention must be paid to details of specimen collection, freezing, and fixation in order to inhibit receptor degradation and false negative results.