Understanding breast cancer — Classification of breast cancer
IN our ongoing efforts to raise breast cancer awareness and encourage annual self-examinations for women, we are launching the ‘Understanding Breast Cancer’ series in the coming weeks. This series aims to deepen knowledge of the disease, including risk factors, classification and management strategies.
The goal is to bridge the knowledge gap in breast cancer education in Jamaica. Research has shown that essential knowledge and positive attitudes towards breast cancer is often lacking in developing countries with predominant Afrocentric communities.
Breast cancer is a heterogeneous (mixed) disease rather than a single disease, in which cells typically from the ductal lobular components of the breast grow independently from the usual cell regulatory mechanisms. These cells develop the ability to invade nearby structures and spread to distant organs. The appreciation and understanding of this mixed disease model have been significant in advancing the contemporary understanding of breast cancer and improving its long-term prognosis.
Histologically, approximately 99 per cent of breast cancers arise from the ducto-glandular/lobular tissue, while one per cent originate from the stromal/supporting tissue of the breast. Those arising from the ducto-glandular tissues are referred to as adenocarcinomas and are the usual types of breast cancer that we see in any population. Those arising from the stromal/supporting tissue are referred to as sarcomas.
Adenocarcinomas can exist in two forms: in-situ, known as ductal carcinoma in-situ (DCIS), or invasive. In our population, approximately 95 per cent of adenocarcinomas are invasive, compared to 80 per cent in high-income countries. This discrepancy is primarily attributed to more effective population-based screening in those countries, in contrast to the situation in Jamaica.
Invasive adenocarcinomas can be categorised into two groups: special type in 25 per cent of patients and non-special type in 75 per cent. These special types often have a different prognosis and may require different treatment approaches, particularly in terms of surgery and subsequent chemotherapy/radiation therapy.
It is important to know and understand the specific histologic subtype of the breast cancer prior to commencing treatment. The tubular, mucinous and adenoid cystic tend to carry good long-term survival and may not require chemotherapy as part of the management protocol. The metaplastic subtypes are notoriously aggressive and are generally associated with poor long-term survival.
Luminal A – Excellent long-term survival.
Luminal B – Excellent/Good long-term survival with appropriate multidisciplinary treatment. [Usually requires chemotherapy and targeted anti-HER 2 therapy].
HER 2 Over-expressed – Good long-term survival with appropriate multidisciplinary treatment. [Usually requires chemotherapy and targeted anti-HER 2 therapy].
Triple Negative – Least favourable long-term survival, but this is not a uniformed group as there is a variable subgroup with good outcomes.
Prior to any definitive treatment of a patient with breast cancer, it is extremely important to ascertain the receptor/molecular subtype. The combination of the receptor/molecular subtype, the histologic subtype and the clinical stage are the most important determinants of breast cancer treatment and survival outcomes in the contemporary management of breast cancer.
Dr Jason Copeland is a fellowship trained Breast surgeon, breast surgical oncologist (Roswell Park, Buffalo, New York) and consultant general surgeon. He is the founder and clinical director of the Breast Health & Oncology Care Centre at the Andrews Memorial Hospital. He is the clinical director of the Kingston Public Hospital Breast Oncology Clinic and is an associate lecturer at The University Hospital of the West Indies.