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Suzanne,
The answer to your question is in buried in the Background section of the abstract in the post:
"Gene expression profiling of breast cancer has identified two biologically distinct estrogen receptor (ER)-positive subtypes of breast cancer: luminal A and luminal B. Luminal B tumors have higher proliferation and poorer prognosis than luminal A tumors."
The two subtypes have to do with being ER+. The Luminal A group is what I have heard referred to as "garden variety" bc: ER+ PR+ Her2-. It is frequently low grade, slow growing, with moderate to high ER+ and PR+, responsive to endocrine therapy but not particularly sensitive to chemotherapy. The Luminal B cancers are more of a catchall for anything that is technically ER+ but NOT classified as Luminal A, with higher grade and a tendency for proliferation. Triple positives are usually clumped into this group. The point of this study was that an expensive Oncotype Dx test isn't needed to distinguish the "low risk" Luminal A's from the "high risk" Luminal B's, all you need to do is look at the Ki-67 score, which is a measure of proliferation. I pointed out since I have a blend of factors from both Luminal A (high ER+, moderate PR+, low Ki-67) and Luminal B (Her2+), I don't know how I truly should be classified, especially if Ki-67 is the deciding factor.
Hopeful
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