What Are Clear Margins in Breast Cancer Surgery?
Partnership note: I work with Perimeter Medical Imaging AI in a paid partnership as a patient advocate.
Two days after my lumpectomy in 2019, my phone rang, and I didn’t recognize the number. I wasn’t expecting any more medical calls after my surgery, but I answered, just in case it might be important.
I’m so glad I did.
It was my breast surgeon. “Jennifer, I’m between surgeries, but I wanted to let you know that we got the pathology back, and the margins were clear!”
I wanted to scream and jump up and down, but I’d had my lumpectomy just two days earlier, so that was a terrible idea. I thanked him for calling and told him I’d see him at my follow-up the next week.
Then I started telling everyone. Dave, my family, anyone who would pick up the phone. Clear margins meant I didn’t need a second surgery, and I could move on to the next phase of my treatment. I was so relieved.
I slept so much better that night.
What are cancer margins?
Margins are an important part of cancer surgery, and the guidance is different depending on the type of cancer you have. Before we get into that, let’s talk about what a margin actually is.
Your surgeon’s goal is to remove the cancer, and also a small rim of normal tissue around it. That additional tissue is what’s referred to as a margin.
Think of it like the margins around a page in a book. The empty space is the margin, and how big it needs to be depends on the type of cancer you have.
Margins matter because they are associated with recurrence risk. When cancer is removed with a clear margin, the risk of recurrence in that breast is lower. (Reference Link)
Margin Terms You Might See or Hear
Like most things in breast cancer, there are lots of terms used when talking about margins and pathology. The graphic here shows an illustration of each of them.
Clean or clear margins means that there is a rim of healthy tissue around the cancer. This is also referred to as negative margins on many pathology reports, which can be a bit confusing because most of the time we read negative as bad. But in the case of lumpectomy margins, it is good news.
Positive margins means there are cancer cells right at the edge of the tissue that came out. This means the margins were not clear (cancer was left behind), and an additional surgery may be needed to clear them.
Close margins indicate that there wasn’t cancer on the edge of the removed tissue, but that the cancer is close to the margin. If this is the case, then your team will need to discuss what the best options for you would be based on that pathology report.
How big of a margin is necessary?
Margin guidance varies by cancer type, so I encourage you to ask your surgeon what margin would be considered clear for your case. For DCIS, the standard of care is 2 mm of healthy tissue around the DCIS.
Now, I can say 2 mm, and some of you will go get a ruler out. If you don’t have one sitting next to you, here are a couple of other images to consider.
A nickel is about 2 mm thick. You could also think of a tangerine. The peel is thinner than an orange, and that peel could be the rim of normal tissue surrounding the cancer that is removed.
How do they check my margins?
Final pathology is done after your surgery is completed. Once the cancer is removed, the tissue will be inked on all of the sides, so that the medical team knows where each side came from. This is important because in pathology, the tissue is sectioned and viewed carefully under a microscope.
That report typically takes 2 to 7 days to get back. That’s a long time to wait for results.
There are additional methods that may be used, during your surgery, to check your margins. Perimeter Claire™ is one of them. Claire™ is an adjunctive tool that surgeons can use to evaluate the margins at the microscopic level while you are still in the operating room.
What happens if the margins aren't clear?
If your margins come back positive or close, your surgeon may recommend a second surgery to clear them. That’s called a re-excision. A re-excision is another lumpectomy where the surgeon will go in and take additional tissue from the area that still showed cancer on the margins. In some cases, a mastectomy may be recommended.
Research shows that 21% of lumpectomies require a re-excision. The re-excision rate varies significantly between surgeons, based on the type of cancer, and even on the age of the patient. I didn’t realize before I went into a lumpectomy that the reoperation rates are much higher for women under 65, like me.
As you head into surgery, I highly recommend you talk to your surgeon about her reoperation rate, and ask if she uses any additional techniques in the operating room to check margins while you are still in surgery.
Can margins be checked in the operating room?
Not every surgeon has a tool to check for microscopic cancer along the margins during surgery. Since my lumpectomy in 2019, the tools for evaluating margins have continued to advance.
Perimeter Claire™ is one tool that can be used during breast cancer surgery to evaluate margins. It has the ability to see at the microscopic level, in real-time, right in the operating room, but was not yet available to my surgeon at the time of my lumpectomy.
Here’s how Claire fits into surgery. Your surgeon removes the tissue from your breast, and that tissue is then scanned on all six sides with OCT, which stands for optical coherence tomography. OCT is like an ultrasound, but instead of sound waves it uses light. It’s designed to see through the entire 2 mm margin, the standard of care for DCIS, at the microscopic level.
Claire’s AI then identifies suspicious areas for your surgeon to review. It is like your surgeon has an AI-enabled extra set of eyes in the operating room.
Claire is an adjunctive margin assessment tool, which means it supports your surgeon’s own evaluation rather than replacing it. Your surgeon can look at those areas to review while you’re still in the operating room under anesthesia, and take additional tissue if it’s needed.
Claire’s AI doesn’t diagnose a margin as positive or negative; instead, it flags suspicious tissue. Claire is designed as a human-AI team, where the AI acts as a screening tool and your surgeon provides the clinical judgment and makes the call.
Pathology remains the gold standard for final margin measurements and diagnosis, an analysis that takes several days.
All of this matters especially with DCIS, which is challenging to detect while operating because it often feels and looks the same as healthy tissue. I’ll be writing more about that particular challenge in another post.
How did my surgeon get clear margins?
At my follow-up appointment, I read through my pathology report. The notes showed that the first piece of tissue my surgeon removed didn’t have 2 mm of margin around the DCIS. He had gone back in during that same surgery and taken more, and the second specimen was clear. I had been asleep for all of it.
I didn’t realize that my surgeon checked margins during surgery using a technique called frozen section. When I asked him about it, he mentioned that he worked closely with the pathologists at the hospital during his lumpectomies to check the margins.
Frozen section isn’t widely used in breast cancer surgery because it is highly resource intensive, requiring pathology teams to be on call during surgeries. It is considered a sampling technique, meaning it doesn’t look at all of the margins, just selected parts of the tissue and is not as accurate as the final pathology review performed after the surgery. (Reference link one, Reference link two)
He shared with me that his re-excision rate was 8 percent. That’s extremely low, and it made sense to me once I understood what he was doing in the operating room.
I’m so grateful he checked, because I would have been headed back into another lumpectomy if he hadn’t checked.
Clear margins meant that I was able to move on to radiation after recovery and finish my treatment before Christmas 2019.
Margins are such an important part of our cancer treatment, and I hope this has been helpful to explain what margins are and how they are evaluated.
I didn’t know all the questions I could ask before my lumpectomy, especially about re-excision rates or techniques to check margins during surgery.
I’ve worked with Perimeter to put together a list of questions you can take with you to your next appointment. Feel free to head over there and get a copy for yourself.
Disclosures
This post is produced in partnership with Perimeter Medical Imaging AI. You can read more about my policies here .
The content in this post is general education and information and is not to be considered medical advice. Always talk with your medical team about your care.
The Claire OCT System is an adjunctive three-dimensional imaging tool which provides volumetric cross-sectional, real-time depth visualization, coupled with an artificial intelligence computer aided detection algorithm which identifies and marks focal areas suspicious for breast cancer and is used concurrently with physician interpretation of the images.
The Claire OCT System is intended for use in conjunction with other standard methods for evaluation of the margins of excised lumpectomy tissue during surgical procedures in patients with a biopsy-confirmed diagnosis of breast cancer.
The Claire OCT System is an adjunctive tool; it does not replace standard tissue histopathology nor provide a diagnosis. For regulatory and important safety information about Claire, please visit https://perimetermed.com/claire-disclosures/.
References
- Margins and Recurrence: Ezzat A, Shanthakumar D, Laskar N, Cutress RI, Hadjiminas D, Boland M, et al. Impact of resection margin width on local recurrence following breast-conserving surgery and whole breast radiotherapy for pure ductal carcinoma in situ: a systematic review and meta-analysis. BMJ Oncology. 2025;4:e000633. https://doi.org/10.1136/bmjonc-2024-000633
- Re-excision: Kim, Y., Ganduglia-Cazaban, C., Tamirisa, N. et al. Correction: Contemporary Analysis of Reexcision and Conversion to Mastectomy Rates and Associated Healthcare Costs for Women Undergoing Breast-Conserving Surgery. Ann Surg Oncol 31, 3956 (2024). https://doi.org/10.1245/s10434-024-15212-0
- Frozen Section One: Garcia, M. T., Mota, B. S., Cardoso, N., et al. (2021). Accuracy of frozen section in intraoperative margin assessment for breast-conserving surgery: A systematic review and meta-analysis. PLOS ONE, 16, e0248768. https://doi.org/10.1371/journal.pone.0248768
- Frozen Section Two: Li, W., & Li, X. (2022). Development of intraoperative assessment of margins in breast conserving surgery: a narrative review. Gland Surgery, 11, 258–269. https://doi.org/10.21037/gs-21-652
Jennifer Douglas
Jennifer Douglas is an author, patient advocate, and DCIS breast cancer survivor. After navigating her own breast cancer journey in 2019, she began writing and encouraging others who were newly diagnosed. Her resources include her book, "A Breast Cancer Journey: Living It One Step at a Time," and her online support course, "Encourage: Breast Cancer and Beyond." Jennifer also actively supports patients through her online presence and direct involvement in communities and support groups, offering guidance and encouragement every step of the way.
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