Epithelial and Stromal Estrogen and Progesterone Receptor Expression in Endometrial Cancer: True Color Computer-Assisted Image Analysis versus Subjective Scoring

Immunohistochemical methods provide the opportunity to evaluate the staining reaction in different histologic compartments of malignant tumors. Eighty-four formalin-fixed, paraffin-embedded and immunohistochemically stained endometrial cancer specimens were assessed for estrogen receptor (ER) and progesterone receptor (PR) expression by conventional light microscopy, a light microscopy scoring system, and by true color computer-assisted image analysis. Measurements of mean optical density (MOD) in the epithelium as well as in the stroma of the tumor were performed. A negative correlation was established between the MOD of ER and PR staining in the nuclei of the epithelium and the MOD of PR staining in the stroma of the tumor vs histological stage (Spearman correlation coefficient −0.32/P< 0.004, −0.23/P< 0.03, −0.26/P< 0.02, respectively) and depth of myometrial invasion (Spearman correlation coefficient −0.34/P< 0.002, −0.24/P< 0.02, −0.25/P< 0.02, respectively). The staining pattern in endometrial cancer was heterogeneous and %PA (percentage of positive stained area) and MOD were therefore linked by multiplication in order to correct for this potentially confounding phenomenon. A negative correlation with histological stage (Spearman correlation coefficient −0.29/P< 0.007) and depth of myometrial invasion (Spearman correlation coefficient −0.34/P< 0.001) was found for PR staining in the stroma of the tumor. MOD and subjective ranking of staining intensity showed a high correlation as well as %PA and subjective estimation of stained surface. ER and PR content in the epithelium and also PR content in the stroma of endometrial cancer appear to be of value in the assessment of steroid hormone receptor status. This may be indicative of stromal–epithelial interaction.