Ductal Carcinoma In Situ, often referred to as DCIS, represents a non-invasive form of breast cancer where abnormal cells are confined to the milk ducts and have not spread into surrounding breast tissue. When DCIS is diagnosed, a common approach to treatment involves a lumpectomy, a surgical procedure also known as breast-conserving surgery. This surgery aims to remove the cancerous tissue while preserving as much of the healthy breast as possible. Evaluating the success of this removal involves examining the “surgical margins” of the excised tissue to determine if all cancerous cells were effectively removed.
Defining Surgical Margins in DCIS
A surgical margin in the context of a DCIS lumpectomy refers to the border of healthy, normal tissue that surrounds the cancerous area removed by the surgeon. During the lumpectomy procedure, the surgeon excises the tumor along with a surrounding buffer zone of apparently healthy tissue.
Immediately after removal, the entire specimen is sent to a pathologist for detailed examination. To help the pathologist orient the tissue, the surgeon applies different colored inks to the surface of the removed tissue. This allows precise mapping of the edges for accurate margin analysis.
The pathologist then carefully examines the inked edges of the tissue under a microscope. This microscopic assessment determines whether cancer cells are present at the very edge of the removed specimen. The goal is to confirm that the entire cancerous lesion has been successfully removed. This analysis of the inked margins is a standard procedure following breast-conserving surgery for DCIS.
Understanding Margin Status
The pathologist’s report classifies the surgical margins into distinct categories, providing clarity on the completeness of the cancer removal. A “negative margin,” also known as a clean margin, signifies that no cancer cells were found at the inked edge of the removed tissue when viewed under the microscope. This outcome indicates that the surgeon likely removed all the cancerous cells along with a buffer of healthy tissue.
Conversely, a “positive margin” means that cancer cells are present at the very inked edge of the removed tissue. This finding suggests that some cancerous cells may have been left behind in the breast. A “close margin” indicates cancer cells are very near the inked edge, typically within 2 millimeters, but not touching it. These classifications guide subsequent treatment decisions.
The Standard for an Acceptable Margin
For DCIS treated with lumpectomy followed by radiation therapy, a widely accepted standard for an adequate margin is at least 2 millimeters. This consensus guideline was established by major oncology organizations, including the Society of Surgical Oncology (SSO), the American Society for Radiation Oncology (ASTRO), and the American Society of Clinical Oncology (ASCO).
The 2-millimeter standard exists to achieve a balance between thoroughly removing enough tissue to minimize the risk of cancer recurrence and preserving as much healthy breast tissue as possible. Evidence suggests wider margins do not further reduce recurrence, meaning removing more tissue than this standard offers no additional benefit. Adhering to this guideline helps standardize treatment approaches and aims to optimize patient outcomes after breast-conserving surgery for DCIS.
Procedures for Positive or Close Margins
When a pathology report indicates a positive margin, where cancer cells are present at the inked edge, the primary recommendation is typically a re-excision surgery. This procedure involves the surgeon returning to the area of the initial lumpectomy to remove additional tissue from where the margin was positive. The aim is to achieve a clear margin, ensuring no cancer cells remain in the breast. Re-excision rates for positive margins are substantial, often requiring a second surgery.
For close margins, where cancer cells are very near but not touching the inked edge, the decision regarding further surgery can be more nuanced. While some guidelines recommend considering re-excision for margins less than 2 millimeters, the choice often depends on various factors such as the patient’s age, the grade and size of the DCIS, and whether radiation therapy is planned. A multidisciplinary team involving the surgeon, pathologist, and radiation oncologist may discuss these factors to determine the most appropriate next step. In situations where clear margins cannot be achieved even after multiple re-excisions, or if the extent of DCIS is widespread, a mastectomy might be considered as a more extensive surgical option to remove all breast tissue.
Margin Status and Recurrence Risk
Achieving clear surgical margins after a DCIS lumpectomy significantly lowers the chance of local recurrence (IBTR). Positive margins, where cancer cells are at the edge of the removed tissue, are consistently associated with a higher risk of local recurrence. The presence of adequate negative margins is therefore a primary objective of breast-conserving surgery.
Evaluating and addressing margin status aims to reduce the long-term risk of DCIS recurrence. Even when clear margins are achieved, other treatments like radiation therapy are often recommended after a lumpectomy for DCIS to further diminish recurrence risk. This combined approach of surgical removal with clear margins and radiation therapy provides comprehensive local control and improves the long-term outlook for DCIS patients.