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C50.911
C50.911

C50.911: Malignant neoplasm of unspecified site of right female breast

The ICD-10-CM code for primary breast cancer in the right female breast when the specific site within the breast is not documented.

Billable
FY2027

TABLE OF CONTENTS

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TABLE OF CONTENTS

At a glance

Code Family

C50: Malignant neoplasm of breast.

DRG Grouping

MS-DRG 597, 598 or 599 (Malignant Breast Disorders) as principal diagnosis under the FY2027 MS-DRG v44 grouper. A mastectomy admission groups to MS-DRG 582 or 583 (Mastectomy for Malignancy).

HCC Mapping (v28)

HCC 23: Prostate, Breast, and Other Cancers and Tumors.

Condition

Breast cancer

Family Specificity

C50 codes vary by site within the breast, laterality and sex. C50.911 is unspecified site, right breast, female.

Which C50 code do I assign?

C50 codes encode three axes at once: site within the breast, laterality and sex. The C50.A codes for inflammatory neoplasm carry laterality only. A change in any one axis produces a different code.

When documentation says…
Code
Right female breast, site within breast not documented
C50.911
Assign when imaging and pathology do not identify the quadrant, nipple, areola or axillary tail.
Right female breast, upper-outer quadrant
C50.411
Assign the site-specific code whenever the site is named. The same pattern applies to the other quadrant codes.
Left female breast, site not documented
C50.912
Laterality is an axis. It must match the documented affected breast.
Inflammatory breast cancer, right breast
C50.A1
Requires the provider's documented diagnosis of inflammatory breast cancer, the inclusion term at C50.A. The C50.A codes carry no sex axis.
Right male breast
C50.921
Sex is an axis, not an edit.
Female breast, laterality not documented
C50.919
Check the full record for laterality, then query the provider before defaulting here.

Tabular notes

USE ADDITIONAL: HORMONE RECEPTOR STATUS

Category C50 instructs: use additional code to identify estrogen, and other hormones and factors receptor status (the Z17 codes). Z17.0 (ER+) and Z17.1 (ER-) report estrogen receptor status. Progesterone, HER2 and combined receptor status have their own codes in subcategories Z17.2, Z17.3 and Z17.4. Report each status that is documented. A Use Additional code always sequences after C50.911. It is never the principal diagnosis.

EXCLUDES1

Category C50 carries an Excludes1 note for skin of breast (C44.501, C44.511, C44.521, C44.591). A malignancy of the skin of the breast takes one of those C44 codes, not a C50 code.

INFLAMMATORY BREAST CANCER CODES

Subcategory C50.A covers malignant inflammatory neoplasm of breast: C50.A0 (unspecified breast), C50.A1 (right breast) and C50.A2 (left breast). Its inclusion term is inflammatory breast cancer (IBC). Unlike the rest of C50, these codes carry laterality only and no sex axis.

FY2027: EFFECTIVE 1 OCTOBER 2026

FY2027 changed the note for malignant neoplasm of breast (C50.-) at category D05, carcinoma in situ of breast, from Excludes2 to Excludes1. FY2027 also adds QA1.790 and QA1.791, familial cancer syndrome with pathogenic BRCA1 or BRCA2 mutation. Category QA1 carries a Code also note for associated malignant neoplasms. C50.911 is unchanged in the FY2027 update.

Operational & financial impact

Why specificity matters beyond the chart: risk adjustment, DRG assignment and denial exposure all follow from which C50 code is selected.

CMS-HCC v28 (PY2024+)

HCC 23: Prostate, Breast, and Other Cancers and Tumors.

CMS-HCC v24 (legacy)

C50.911 mapped to HCC 12: Breast, Prostate, and Other Cancers and Tumors. CMS-HCC v28 carries the full risk score for payment year 2026.

RECAPTURE REQUIREMENT

Active malignancy must be documented at a qualifying encounter in each data collection year. Z85.3 (personal history) does not map to HCC 23. HCC 23 is not captured in a year when only Z85.3 is reported.

INPATIENT

Surgical admissions (mastectomy, lumpectomy) group to breast-surgery DRGs. Medical admissions group by the principal diagnosis. When an admission treats a complication of the malignancy or its therapy, Guideline I.C.2.c can make the complication the principal diagnosis.

Documentation checklist to support C50.911

Chart elements that support code selection and reduce specificity-driven denials.

FAQ

Is C50.911 a billable code?

Yes. C50.911 is a billable/specific ICD-10-CM code valid for reimbursement in the FY2027 code set, effective 1 October 2026.

What is the difference between C50.911 and C50.A1?

C50.911 covers malignant neoplasm of the right female breast when the site within the breast is not documented, any type except inflammatory. C50.A1 covers malignant inflammatory neoplasm of the right breast. When the provider documents inflammatory breast cancer, C50.A1 replaces C50.911.

What is the difference between C50.911 and C50.919?

The difference is laterality. C50.911 is the right breast. C50.919 is used when laterality is not documented. Check the full record for laterality before using C50.919. When laterality is not found, C50.919 should prompt a query rather than be assigned by default.

Should Z85.3 or C50.911 be used once treatment is finished?

Use Z85.3 (personal history of malignant neoplasm of breast) when the cancer was excised or eradicated and no further treatment is directed to the site. There must also be no evidence of existing malignancy there (Guideline I.C.2.m). C50.911 stays while treatment is still directed to the site. The transition point is the provider's documentation, not elapsed time.

Does C50.911 map to a Medicare HCC?

Yes. C50.911 maps to HCC 23 under CMS-HCC v28. The mapping requires active malignancy documented at a qualifying encounter in each data collection year. A history code does not recapture it.

Related codes

Codes in the same family as C50.911. Only codes with a published page render as links.

Sibling codes in the C50 family

  • C50.912: Malignant neoplasm of unspecified site of left female breast.
  • C50.919: Malignant neoplasm of unspecified site of unspecified female breast.
  • C50.411: Malignant neoplasm of upper-outer quadrant of right female breast.
  • C50.A1: Malignant inflammatory neoplasm of right breast.
  • C50.921: Malignant neoplasm of unspecified site of right male breast.

Additional codes to consider

Codes outside the C50 family considered alongside C50.911.

Companion: code alongside when documented

  • Z17.0: Estrogen receptor positive status [ER+].
  • Z17.1: Estrogen receptor negative status [ER-].
  • Z15.01: Genetic susceptibility to malignant neoplasm of breast, where documented. Subcategory Z15.0 carries a Code first note for any current malignant neoplasm.

Consider instead

  • C50.A1: Malignant inflammatory neoplasm of right breast (use instead of C50.911 when inflammatory breast cancer is documented).
  • Z85.3: Personal history of malignant neoplasm of breast (use when the breast cancer was excised or eradicated, no further treatment is directed to the site and no existing malignancy remains, per Guideline I.C.2.m).
  • C77.0–C79.9: Secondary malignant neoplasm at the metastatic site (coded in addition to the primary, not instead of it).
  • C44.501: Unspecified malignant neoplasm of skin of breast, where the lesion is skin of breast rather than breast tissue.

Sources

All claims on this page derive from government and professional-standards sources.

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