Luminal breast cancer subtypes are characterized by estrogen-receptor and estrogen-related genes, which sets them apart from other tumors that are not hormonally driven.
“Luminal B tumors have lower estrogen gene expression, and have higher expression of more proliferative types of genes,” says Angela DeMichele, MD, MSCE, professor of medicine and epidemiology, University of Pennsylvania.
So, whereas estrogen-receptor positive breast cancers don’t divide very quickly, “luminal B tumors are different. These tumors, while still having estrogen-related cell expression, are actually now dividing much more quickly due to the existence of these proliferative genes.”
In addition, estrogen-receptor positive breast tumors have “unique patterns of recurrence,” and reasons for this are not very well understood. It may be due to resistance, says Dr. DeMichele.