Your Pathology Report

A pathology report is created when a tissue or cell sample is tested for cancer or other abnormalities. This includes results from a biopsy (small tissue sample), a lumpectomy (tumour and some surrounding tissue), or a mastectomy (removal of the entire breast).

The report provides key details about the diagnosis, guiding treatment decisions. It includes:

Structure of a Pathology Report

• Specimen Description: Where the tissue was taken from and how it was collected

• Macroscopic Findings: Size, shape, and appearance of the sample

• Microscopic Findings: How cells look under a microscope, including cancer presence and aggressiveness
• Additional Tests: Specialized tests for hormone receptors (HR), HER2 status, and other biomarkers.

Cancerous vs. Non-Cancerous Cells
The pathology report determines whether the sampled cells or tissue are cancerous or non-cancerous:

• Non-cancerous (benign) cells: No cancer is found, but follow-up may be recommended
• Cancerous (malignant) cells: Cancer is present. The report will indicate whether the cancer is:
  • Non-invasive (in situ): Cancer has not spread beyond ducts or lobules
  • Invasive: Cancer has spread into surrounding breast tissue

Tumour Grade and Nuclear Grade
Tumour grade shows how different cancer cells are from normal ones and predicts how fast they grow and spread:

• Grade 1 (Low): Cells look slightly different from normal cells and grow slowly
• Grade 2 (Intermediate): Cells look less normal and grow at a moderate rate
• Grade 3 (High): Cells look very abnormal, grow quickly, and may spread aggressively

Nuclear grade refers to how abnormal the cell’s nucleus (centre) appears, often linked to tumour aggressiveness. Some reports include Ki-67, a marker of how quickly cells are dividing.

Surgical Margins
Surgical margins show if cancer is present at the tissue edges after surgery:

• Negative (Clear): No cancer at the edges and additional surgery is likely not needed
• Positive: Cancer cells at the edges and further surgery may be required
• Close: Cancer cells are near but not at the edge and your healthcare team will assess the need for further surgery

Lymphovascular Invasion (LVI) and Lymph Node Involvement
LVI: Cancer cells are found in the blood or lymph vessels within the breast, increasing the risk of spread. LVI is reported as either:

• Absent: No cancer found in these vessels
• Present: Cancer cells are found, suggesting a higher risk of recurrence or metastasis

Lymph Node Involvement: Lymph nodes help filter harmful substances, including cancer cells. The pathology report will indicate if cancer is present in the lymph nodes:

• Negative: No cancer found in lymph nodes
• Positive: Cancer is present in one or more lymph nodes, increasing the risk of spread

The report may specify:

• The number of affected nodes
• The extent of cancer in each node
• Whether cancer has spread beyond the nodes

HR and HER2 Status
Your pathology report will also include HR status and HER2 status, which help guide treatment decisions.

• HR status: Breast cancer may have estrogen (ER) or progesterone (PR) receptors. If positive, hormone therapy may be effective.
• HER2 status: HER2 positive cancers have high levels of HER2 protein, which promotes growth. Targeted treatments may be recommended.

Additional Biomarker Testing
In some cases, additional biomarker tests may be ordered to further guide treatment. These are not always included in standard pathology reports but may be requested by healthcare providers if they could impact treatment options. These include:

• ESR1 Mutations (HR positive breast cancer): These mutations can make hormone therapy, especially aromatase inhibitors, less effective. They are more common in metastatic breast cancer. ESR1 mutations are detected through next-generation sequencing (NGS) or liquid biopsy.

• PIK3CA Mutations (HR positive/HER2 negative breast cancer): Found in about 40% of HR positive/HER2 negative breast cancers, these mutations help cancer grow. People with metastatic breast cancer may benefit from PI3K inhibitors like alpelisib (Piqray), combined with hormone therapy.

• PD-L1 Expression (triple negative breast cancer - TNBC): This test helps determine if someone with TNBC is eligible for immune checkpoint inhibitors (a type of immunotherapy). PD-L1 levels are measured using an immunohistochemistry (IHC) test. This test is mainly used in advanced or metastatic TNBC.

Learn More
For more information about pathology reports, visit:

• MyPathologyReport.ca: A patient-friendly resource to help you understand your pathology report
• Workshop: Understanding Your Pathology Report: A CBCN resource providing further guidance

Understanding your pathology report can help you make informed decisions and actively participate in your treatment plan. If you have questions about any part of your report, speak with your healthcare team.

Medical Review by Roochi Arora, MD, FRCPC, August 2025

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