Use of cultured cells as a control for quantitative immunocytochemical analysis of estrogen receptor in breast cancer - The Quicgel method

Variation in tissue fixation, processing, and staining is largely responsib le for poor reproducibility of estrogen receptor (ER) immunohistochemistry assays. A frozen, agar-suspended pellet of MCF-7 cells with known ER conten t was added to each of 55 samples of invasive breast carcinoma (IBC), sewin g as a control. Image analysis determined percentages of positive area (pos itive nuclei per total nuclei analyzed) and positive stain (sum of optical density of the positive nuclear area divided by sum of the optical density of all nuclei studied) of MCF-7 cells and IBC. MCF-7 cells had a mean value of 150 fmol/mg of ER by dextran-coated charcoal analysis. Image analysis o f MCF-7 cells included with the 55 cases showed a mean positive area of 70. 81. Positive staining from the IBC cases ranged from 0 to 98.5. By using th e known ER content and the positive area of the MCF-7 cells, a conversion f actor was used to translate the positive area of the clinical specimens to a femtomole equivalent, which for the 55 IBCs ranged from 0 to 1,790 (mean, 187). Inclusion of a control with known femtomole quantity of ER provides an internal standard for quality control and ER quantitation.