When you’re getting diagnosed with breast cancer, the last thing you need is to receive a hard-to-understand pathology report. Have you recently received a pathology report that stated “unspecified laterality”? Do you feel like you understand what “laterality” means in the context of receiving your diagnosis?

When receiving your initial breast cancer 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. The report includes detailed information about your tumor size, how much it has spread, and what stage of breast cancer you have. It also contains technical information on the histologic grade (how the cells of the tumor look), what molecular markers the cancer has, and whether it has metastasized (spread) to distant organs and lymph nodes.

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 will describe one portion of the report that may not be immediately obvious: laterality.

What Is Laterality?

“Laterality” is a term used in clinical settings to describe how a condition affects one side of the body. 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 that need to be differentiated from one another in certain situations.

In the pathology report, laterality describes the breast where the primary tumor originated. Laterality is one feature of the anatomic site (or body site) that the pathology report describes. It also will describe the severity and grade of different characteristics of your tumor.

There are three general options for laterality of a primary tumor in breast cancer:

• Left
• Right
• Unspecified

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. More people have left-side laterality, and genes can play a role in which side your tumor starts. The term “unspecified laterality,” on the other hand, may leave you with questions.

What Does Unspecified Laterality Mean?

The term “unspecified laterality” means that your oncologist could not determine from the biopsy which breast the primary tumor originated from. This may occur if both breasts have cancer at the time of your diagnosis. Even with taking several biopsy samples from each breast, it might not be possible to determine where the tumor started.

Your doctor also may indicate unspecified laterality if only one breast was sampled for a biopsy and it’s unclear if that’s where the primary tumor started.

Unspecified laterality could also occur in a bilateral mastectomy, where both breasts were removed. Unspecified laterality may be indicated if there’s extensive metastasis or the cancer is spreading to distant sites.

For medical billing purposes, the laterality should always be indicated, if possible. If it’s not possible, the reason should be stated. There are specific diagnosis codes used in billing for different unspecified laterality cases.

Why Are There Codes on Your Pathology Report?

Medical diagnoses are given numerical codes for consistency of reporting, reproducibility, and billing purposes. They help doctors and researchers compare trends in diseases across nations.

Diagnostic codes can generally be useful for:

• Standardized research protocols
• Evidence-based research
• Insurance-claim submissions

In terms of billing, these codes may affect whether the insurance company will accept a claim or what kind of treatment you may be able to receive. Medicare and Medicaid make revisions to international guidelines for categorizing diagnosis. The International Classification of Diseases, 10th Revision, Clinical Modification (ICD-10-CM) provides consistent guidelines for diagnosis codes.

When there is a clinical diagnosis of a paired organ, such as the breasts, laterality status is required to be stated. If the pathology results do not provide this information, your clinician may be able to use your personal medical record for this information.

If the primary site of the tumor happened to be bilateral — originating from both breasts — then ICD-10 codes indicate that both left and right breasts should be reported.

The term “unspecified” is used only if the primary site is truly unknown. There are specific ICD-10 codes that should be used if the laterality cannot be determined.

Unless you’re experiencing problems with your insurance company accepting a claim, you don’t need to worry about which code was used.

Should You Be Concerned About Unspecified Laterality on Your Pathology Report?

Seeing “unspecified laterality” on your pathology report isn’t anything to be concerned about. A research study from 2014 looked at more than 300,000 women with diagnosed cases of breast cancer and asked if laterality had any impact on their likelihood of surviving their cancer. The study found that the side on which the tumor originated played no role in survival rates. Even if your doctor doesn’t know the original side of your tumor, it likely won’t play a huge role in your treatment.

Laterality is just one feature of your overall pathology report. Reporting this information may be useful at some point from a research perspective to determine whether certain treatments are more effective when a primary tumor comes from one breast over the other.

If you have any questions about terms or codes on your pathology report, it’s important to talk to your health care provider. They can provide you with any additional information you need to understand your pathology report and why your laterality was unspecified.

Talk With Others Who Understand

On MyBCTeam, more than 64,000 members diagnosed with breast cancer come together to ask questions, give advice, and share their stories with others who understand life with breast cancer.

Are you living with breast cancer? Have you received a pathology report that states “unspecified laterality” or something else that was unclear to you? Share your experience in the comments below, or start a conversation by posting on your Activities page.