Breast Cancer Information/Diagnosis and Testing

Unspecified Laterality on Pathology Report: What Does It Mean?

Medically reviewed by Maybell Nieves, M.D.

Written by Hannah Actor-Engel, Ph.D.

Updated on September 9, 2026

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Key Takeaways

A breast cancer pathology report is an important document that helps you and your care team understand your diagnosis and explore treatment options, but some of the terms in it can be confusing.

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When you’re getting diagnosed with breast cancer, the last thing you need is to receive a hard-to-understand pathology report. What does “unspecified laterality” mean, and why can’t doctors use plain English?

The pathology report is an important tool for helping you and your oncology provider understand your diagnosis and assess treatment options. The report can be technical and hard to interpret, so it’s normal to have a lot of questions about what it means.

Here we’ll describe one portion of the report that may not be immediately obvious: laterality.

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What Does the Pathology Report Show?

When receiving your initial diagnosis, you likely had a procedure called a breast biopsy. Following this procedure, you should have received a pathology report that describes the key characteristics of your cancer.

A pathology report may include information such as:

The type of your cancer

Whether lymph vessels are invaded by cancer cells

The tumor grade

The final diagnosis

Molecular or biomarker test results, such as estrogen receptor, progesterone receptor, and HER2 status

Together, these details can help your oncology team identify the best treatment options for your specific breast cancer.

What Is Laterality in a Breast Cancer Pathology Report?

“Laterality” is a term used in clinical settings to describe which side of the body a condition affects. It’s used in cases where there are paired organs (two of the same organ) that could be referred to in a report. In breast cancer, the left and right breasts are the paired organs being referred to.

In a breast cancer pathology report, laterality describes which breast the tissue sample came from or which breast is affected. Laterality is one feature of the anatomic site (or body site) that the pathology report describes.

Laterality in medical records is usually documented as left, right, or bilateral. “Bilateral” means both sides. In ICD-10-CM coding guidance, some diagnosis codes include a bilateral option.

If the side isn’t identified in the medical record, a code for the unspecified side may be used.

A primary tumor of left or right origin seems relatively easy to understand. It means that the tumor started growing in the left or right breast. The term “unspecified laterality,” on the other hand, may leave you with questions.

What Does Unspecified Laterality Mean?

The term “unspecified laterality” means that the record didn’t identify the affected side clearly enough for a more specific left- or right-side code. It doesn’t necessarily mean your oncologist couldn’t tell which breast had cancer, and it doesn’t mean your cancer is more advanced.

Sometimes wording on a report or bill reflects the information available to the coding team, not every detail your doctor knows about your diagnosis. ICD-10-CM guidance says “unspecified” codes are used when the information in the medical record isn’t detailed enough to assign a more specific code.

The guidance also says codes for an unspecified side should be used rarely, such as when documentation is insufficient and clarification isn’t possible.

If your breast cancer diagnosis report says “unspecified laterality,” ask your doctor what it means in your situation. They may be able to point to another part of the report, your biopsy order, imaging results, or your broader medical record that identifies the side.

If the side is still unclear, your care team can explain whether it matters for your next steps.

Why Are There Codes on Your Breast Cancer Pathology Report?

Medical diagnoses are given numerical codes for consistency of reporting, reproducibility, and billing purposes. Diagnostic codes are important for insurance claims and research projects that look at anonymous patient data and outcomes of cancer cases over time.

That said, diagnosis codes are not the same as your treatment plan.

Unless you’re experiencing problems with your insurance company accepting a claim, you don’t need to worry about which code was used. If a code or term on your pathology report is unclear, your healthcare provider can explain what it means and whether it has any effect on your care.

Should You Be Concerned About Unspecified Laterality?

Seeing “unspecified laterality” on your pathology report or billing paperwork may be confusing, but it often reflects incomplete side documentation rather than a new medical finding. It’s not proof that your cancer started in both breasts, that you need a different treatment, or that your prognosis has changed.

Laterality is just one part of understanding a breast cancer pathology report. Many other details are more central to planning treatment, including the type of breast cancer, tumor size, grade, lymph node status, margin status, stage, and biomarker results.

If you’re still waiting for final pathology, biomarker testing, or imaging, your care team may explain that some details are pending.

If you have any questions about terms or codes on your pathology report, it’s important to talk to your healthcare provider. The doctor in charge of your treatment can tell you about the findings in the report and help you understand what the report means for your situation.

You can also ask who to contact if the report appears to contain an error or if your insurance company asks for additional information.