We updated this breast cancer ICD-10 guide in October 2026 for the FY2027 ICD-10-CM code set, effective October 1, 2026.
Quick answer: Active breast cancer is coded to category C50.- (malignant neoplasm of breast), with codes that build out by site, sex and laterality, for example C50.412 for the upper outer quadrant of the left female breast. Use D05.- for carcinoma in situ, C79.81 only when cancer from another site has spread to the breast, and Z85.3 when the cancer has been excised or eradicated and no treatment is directed at it.
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What are the main ICD-10-CM codes for breast cancer?
| Condition | ICD-10-CM Code | When to Use |
|---|---|---|
| Primary malignant breast cancer | C50.- | Active malignancy that started in the breast |
| Cancer that spread to the breast from another site | C79.81 | Secondary malignant neoplasm of breast only |
| Breast cancer that spread to another site | C50.- plus the secondary site code | For example C78.0- (lung), C78.7 (liver), C79.31 (brain), C79.51 (bone) |
| Carcinoma in situ of breast | D05.- | Non-invasive cancer, such as DCIS (D05.1-) or LCIS (D05.0-) |
| Personal history of breast cancer | Z85.3 | Cancer excised or eradicated, no further treatment directed to the site, no evidence of disease |
| Hormone receptor status | Z17.- | Reported in addition to C50.- (code first the malignancy) |
| Genetic susceptibility to breast cancer | Z15.01 | Confirmed abnormal gene, such as a BRCA mutation |
Key takeaway
- C50.- = active breast cancer
- C79.81 = cancer that spread to the breast from somewhere else
- D05.- = carcinoma in situ (non-invasive)
- Z85.3 = history of breast cancer, no current treatment
How is the C50 code built?
Each C50 code captures three details from the documentation. Assign the most specific code the record supports.
- Site (4th character): nipple and areola (C50.0-), central portion (C50.1-), upper inner quadrant (C50.2-), lower inner quadrant (C50.3-), upper outer quadrant (C50.4-), lower outer quadrant (C50.5-), axillary tail (C50.6-), overlapping sites (C50.8-), or unspecified site (C50.9-).
- Sex (5th character): 1 for female breast, 2 for male breast.
- Laterality (6th character): 1 for right, 2 for left, 9 for unspecified.
Example: C50.412 = malignant neoplasm of upper outer quadrant of left female breast.
Bilateral breast cancer: ICD-10-CM has no bilateral C50 code. Report a separate code for each breast.
CPC exam tip
If the provider documents the quadrant, you must code it. Choosing an unspecified code when the record supports more specificity will cost you points on the exam.
How do you code metastatic breast cancer?
The word “metastatic” can point in two directions, so read the documentation carefully.
- Breast cancer that spread elsewhere: code the primary breast site from C50.- and add the code for each secondary site, such as C79.51 for bone metastasis.
- Cancer from another site that spread to the breast: code C79.81 for the breast, plus the primary site code (or Z85.- if the primary has been excised and is no longer treated).
Which code is sequenced first?
Sequencing follows the reason for the encounter. When treatment targets the primary breast malignancy, list the C50 code first. When the encounter is for treatment directed only at the secondary site, list the secondary neoplasm code first, even if the primary is still present. Always confirm sequencing against Section I.C.2 of the FY2027 ICD-10-CM Official Guidelines.
CPC exam tip
Do not assume metastatic disease. The provider must document it clearly.
When do you use Z85.3 instead of C50?
Use Z85.3 (personal history of malignant neoplasm of breast) when:
- The cancer was excised or eradicated
- No further treatment is directed to the breast
- There is no evidence of existing disease
- The patient is in follow-up or surveillance
Common mistake: using Z85.3 while the patient is still receiving treatment such as chemotherapy or radiation. If treatment is ongoing, the cancer is still coded as active with C50.-.
How do you code hormone receptor and HER2 status?
Report receptor status with Z17.- codes in addition to the C50 code. Code first the malignancy. The category instructs you to use one code, as available, for each receptor.
- Z17.0 estrogen receptor positive and Z17.1 estrogen receptor negative
- Z17.21 and Z17.22 progesterone receptor positive or negative
- Z17.31 and Z17.32 HER2 positive or negative
- Z17.410 and Z17.411 hormone receptor positive with HER2 positive or negative
- Z17.420 and Z17.421 hormone receptor negative with HER2 positive or negative
Are there BRCA and hereditary cancer codes?
Z15.01 (genetic susceptibility to malignant neoplasm of breast) remains valid for a confirmed abnormal gene. The FY2027 update, effective October 1, 2026, also added new codes for familial cancer syndromes, including QA1.790 (familial cancer syndrome with pathogenic BRCA1 mutation) and QA1.791 (familial cancer syndrome with pathogenic BRCA2 mutation). Verify these new codes and their instructional notes in your current year ICD-10-CM code book before reporting them.
For family history of breast cancer without a personal diagnosis, report Z80.3.
Does invasive ductal carcinoma have its own ICD-10 code?
No. “Invasive ductal carcinoma” describes the cell type, not the ICD-10-CM code. IDC is still coded to C50.- based on site, sex and laterality. Ductal carcinoma in situ (DCIS), which is non-invasive, goes to D05.1-.
How do you code breast cancer step by step?
- Determine whether the cancer is active or history only.
- Identify whether it is primary, secondary, or in situ.
- Confirm the site, the sex, and the laterality.
- Assign the most specific C50 (or D05) code.
- Add secondary site codes, Z17 receptor status, and any genetic susceptibility codes the record supports.
- Sequence based on the reason for the encounter.
Pro tip
If you feel stuck, start in the Alphabetic Index, then verify the code in the Tabular List.
Frequently asked questions
What is the ICD-10 code for breast cancer?
Active breast cancer goes to category C50.-. The full code depends on the site in the breast, whether the patient is female or male, and which side the cancer affects, for example C50.911 for malignant neoplasm of unspecified site of right female breast.
Is C79.81 used for metastatic breast cancer?
Only when cancer from another site has spread to the breast. When breast cancer spreads to other organs, code C50.- for the breast and add the code for each secondary site.
When should I use Z85.3?
Use Z85.3 when the breast cancer has been excised or eradicated, no further treatment is directed to it, and there is no evidence of disease.
Is there a bilateral breast cancer code?
No. Report a separate C50 code for the right and the left breast.
Did breast cancer codes change for 2027?
The C50, D05, C79.81 and Z85.3 codes did not change in the FY2027 update. The update also added new familial cancer syndrome codes for BRCA1 and BRCA2 mutations.
For a closely related topic, see our guide to mammography coding guidelines.
Coding Clarified final thoughts
Breast cancer coding is one of the most tested and most used scenarios on the CPC exam and in real-world coding. Success comes from understanding the code structure, applying the guidelines, and practicing real scenarios.
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Use these Medical Coding Tools such as ICD-10 Data and the FY2027 ICD-10-CM Official Guidelines.
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