Figure 2From: The origins of estrogen receptor alpha-positive and estrogen receptor alpha-negative human breast cancerExamples illustrating the wide range of estrogen receptor alpha (ER) expression characteristic of invasive breast cancers (IBCs) (dark nuclei, ER-positive as assessed by immunohistochemistry). (a) A substantial (~25%) subset of IBCs does not contain any ER-expressing cells. The majority (~75%), however, do contain ER-expressing cells, but the proportion varies on an evenly distributed continuum ranging from (b, c) very low, to (d, e) intermediate, to (f) very high.Back to article page