From the Guidelines
Breast cancer originates from the epithelial tissue of the breast, specifically from the cells lining the milk ducts (ductal carcinoma) or the milk-producing lobules (lobular carcinoma), with approximately 85% to 90% of invasive carcinomas being ductal in origin. The malignant transformation occurs when these epithelial cells undergo genetic mutations that disrupt normal cell growth and division mechanisms, as noted in studies such as 1 and 1. These mutations can affect genes responsible for cell cycle regulation, DNA repair, and apoptosis (programmed cell death), leading to uncontrolled proliferation of abnormal cells. The transformed cells can remain within the ducts or lobules (in situ carcinoma) or invade surrounding breast tissue (invasive carcinoma).
Key points to consider include:
- The spectrum of proliferative abnormalities in the breast, including hyperplasia, atypical hyperplasia, in situ carcinoma, and invasive carcinoma, as discussed in 1 and 1.
- The importance of understanding the tissue of origin in guiding treatment approaches, as it explains why breast cancer typically begins in the ducts or lobules before potentially spreading to nearby tissues and lymph nodes.
- Various factors that can influence the development of breast cancer, including genetic predisposition (such as BRCA1/BRCA2 mutations), hormonal factors, and environmental exposures, as mentioned in 1.
Given the information from the most recent and highest quality studies, such as 1, the tissue of origin for breast cancer is primarily the ductal epithelium, with a smaller proportion originating from the lobular epithelium. This understanding is crucial for developing effective treatment strategies and improving patient outcomes.
From the Research
Tissue of Origin for Breast Cancer
The tissue of origin for breast cancer is the epithelial cells lining the ducts or lobules of the breast 2.
Epithelial Cells and Breast Cancer
- Epithelial cells can be divided into light and dark cells using electron density 3
- The normal mammary gland can be roughly divided into the large duct close to the nipple and the terminal duct located within the lobulus, both composed of epithelial cells and myoepithelial cells 3
- Breast cancer arises from epithelial cells lining the breast ducts and lobules 4
Terminal Ductal-Lobular Unit
- The terminal ductal-lobular unit is the site of origin for most breast diseases, including hyperplasias and neoplasia 5
- The terminal ductal-lobular unit is drained by a terminal duct attached to the main duct system 5