How do you reconcile the difference with regard to adjuvant treatment recommendations when a breast biopsy reveals >10% ER+ but a subsequent lumpectomy of the same lesion is ER-negative?

Situations such as this typically involve review with pathology, including a second opinion review, to settle on one of two basic camps of possible explanations:

1. Heterogenous cancer or even possibly multiple primaries with differing receptors. Although not common, some cancers are heterogeneous with areas of lower and higher grade, and differing receptors. Moreover, depending on how ER "positive" the initial biopsy, the cancer might simply be displaying a range, albeit with overall low positi...