Estrogen receptor stain in breast cancer

(A) Strongly ER-positive invasive cancer. Tumor cells exhibit variable intensity of staining in >90% of the cells.
(B) Tumor cells stained for ER show no ER activity. Normal breast ducts, shown at right have variable positivity indicating that the assay can be interpreted.
(C) Breast cancer with variable ER activity in invasive tumor cells. Although many areas are negative, some are strongly positive and the proportion of positive cells is greater than 1%. No intrinsic normal elements (ducts) are seen, but they were also positive in this case.
(D) Illustrates intrinsic controls. Slide shows DCIS at the lower left and normal ducts at the upper right. The DCIS is strongly ER positive.