Breast Cancer Subtypes

By Isabella Martire, MD, Board Certified In Oncology

Breast cancer is a heterogeneous disease, characterized by many subtypes that have distinct molecular biological features. Each subtype is treated differently

Luminal A represents approximately 40% of all invasive breast cancers and it is characterized by estrogen receptor positive or progesterone receptor positive, HER2/neu negative tumors with a low growth rate (Ki67). Luminal A tumors are more common in the older patients and respond well to anti-estrogen therapy (tamoxifen, arimidex, evista, femara etc.).

Luminal B represents 20% of all invasive breast cancers. These cancers are estrogen receptor positive, and/or progesterone receptor positive, HER2/neu positive (or HER2/neu negative but with a high growth rate Ki67). Luminal B tumors are more aggressive and less responsive to hormonal therapy and if HER2/neu positive they need to be treated with anti HER2/neu therapies as well.

Triple negative/basal like represent 15-20% of all invasive cancers, the estrogen progesterone and HER2/neu receptors are all negative. These types of cancers are more common in the younger age group, and are aggressive. They are more common in African American women and in BRCA+ women. These cancers respond to PARP-inhibitors and platinum agents. Therapeutic agents are currently being investigated to better treat triple negative cancers but we have clearly made progress.

HER2/neu type is a cancer characterized by estrogen negative progesterone negative and HER2/neu positive cancers. These cancers represent between 10-20% of all invasive cancers. In addition to chemotherapy, HER2/neu targeted therapies need to be given (Herceptin, TDM, and Tykerb/pertuzumab), the cure rate for these cancers has dramatically improved. Thanks to these targeted agents.