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C50.511 ICD-10-CM Code: Malignant neoplasm of lower-outer quadrant of right female breast

C50.511 maps to CMS-HCC V28 23. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · free HCC coding tools

ICD-10-CM Code View

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Code lookupC50.511

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of breast (C50)

C50.511

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Malignant neoplasm of lower-outer quadrant of right female breast

Cancer that starts in the lower-outer area of the right breast in women. This quadrant is also a common site for breast cancer development.

Buddy the Bee presenting code insight

Buddy Insight

Malignant neoplasm of the lower-outer quadrant of the right female breast represents a common location for breast malignancy.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 23

Code-level coefficient reference

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

N/A

—

Not mapped

ESRD/PACE

N/A

—

Not mapped

RXHCC

HCC 22

Code-level coefficient reference

Code Book Path

Official
C50.5Malignant neoplasm of lower-outer quadrant of breastC50.51Malignant neoplasm of lower-outer quadrant of breast, femaleC50.511Malignant neoplasm of lower-outer quadrant of right female breast

Inclusion Terms

Official

No inclusion terms are included in this display for C50.511. Check the code and parent instructions in the Code Book.

Excludes 2

Official

No Excludes 2 notes are included in this display for C50.511. Check the code and parent instructions in the Code Book.

Related Codes

Official
C50.512Malignant neoplasm of lower-outer quadrant of left female breastC50.519Malignant neoplasm of lower-outer quadrant of unspecified female breast

Includes

Official
  • connective tissue of breastInherited from C50
  • Paget's disease of breastInherited from C50
  • Paget's disease of nippleInherited from C50

Excludes 1

Official
  • skin of breast (C44.501, C44.511, C44.521, C44.591)Inherited from C50

Code First

Official

No Code First sequencing instructions are included in this display for C50.511. Check the code and parent instructions in the Code Book.

Use Additional

Official
  • code to identify estrogen, and other hormones and factors receptor status (Z17.-)Inherited from C50

Code Also

Official

No Code Also instructions are included in this display for C50.511. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Confirmed female patient sex
Laterality documented as right breast
Specific quadrant identified as lower-outer
Histological type and grade (ductal, lobular, etc.)

MEAT Support

HCC Buddy guidance
Confirmed female patient sex
Laterality documented as right breast
Specific quadrant identified as lower-outer
Histological type and grade (ductal, lobular, etc.)

Audit Caution

HCC Buddy guidance
Misidentifying the quadrant from imaging reports — ensure clock position terminology maps to correct quadrant
Using the unspecified site code C50.911 when the quadrant is clearly documented in pathology or imaging
Confusing lower-outer with lower-inner quadrant codes
Not coding bilateral breast cancers separately when both breasts are affected

Common Mistakes

HCC Buddy guidance
C50.411 — Upper-outer quadrant of right female breast; coders may confuse upper vs. lower outer quadrant designations
C50.521 — Lower-outer quadrant of right male breast; wrong gender code — verify patient sex
C50.512 — Lower-outer quadrant of left female breast; laterality error — confirm right vs. left
C50.911 — Unspecified site of right female breast; less specific when quadrant is actually documented

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is C50.511 an HCC code?

Yes. C50.511 (Malignant neoplasm of lower-outer quadrant of right female breast) maps to HCC 23, Prostate, Breast, and Other Cancers and Tumors under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.186. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: C50.511 is billable and maps to V28 HCC 23, Prostate, Breast, and Other Cancers and Tumors. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
C50.511
Description
Malignant neoplasm of lower-outer quadrant of right female breast
HCC (V28)
HCC 23 — Prostate, Breast, and Other Cancers and Tumors
RAF reference coefficient
0.186
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 23, Prostate, Breast, and Other Cancers and Tumors
0.186
RxHCCHCC 22, Prostate, Breast, Bladder, and Other Cancers and Tumors
Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work C50.511 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C50.511

For C50.511, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

  • MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
  • EEvaluate: test results, medication response, or physical findings reviewed by the provider
  • AAssess: explicit mention in the assessment or plan with acknowledgment of status
  • TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Coder workflow notes

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What This Code Means

C50.511 is the ICD-10-CM diagnosis code for malignant neoplasm of lower-outer quadrant of right female breast. Cancer that starts in the lower-outer area of the right breast in women. This quadrant is also a common site for breast cancer development. C50.511 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of breast (c50).

Under the CMS-HCC V28 risk adjustment model, C50.511 maps to Prostate, Breast, and Other Cancers and Tumors (HCC 23) with a source-labeled community, non-dual, aged reference coefficient of 0.186. No V24 mapping is shown for C50.511; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

Confirm the tumor location is lower-outer quadrant, not upper-outer or other locations. For C50.511, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for C50.511 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Confirm the tumor location is lower-outer quadrant, not upper-outer or other locations
  • •Verify right breast laterality is clearly documented before assigning this code

Clinical Significance

Malignant neoplasm of the lower-outer quadrant of the right female breast represents a common location for breast malignancy. The lower-outer quadrant is the second most common site for breast cancer after the upper-outer quadrant. Precise quadrant documentation supports accurate tumor mapping and surgical planning.

Documentation Requirements

  • ✓Confirmed female patient sex
  • ✓Laterality documented as right breast
  • ✓Specific quadrant identified as lower-outer
  • ✓Histological type and grade (ductal, lobular, etc.)
  • ✓Tumor size and TNM staging
  • ✓Receptor status (estrogen receptor, progesterone receptor, HER2)
  • ✓Current treatment status and whether disease is active or in remission

Commonly Confused Codes

  • •C50.411: Upper-outer quadrant of right female breast; coders may confuse upper vs. lower outer quadrant designations
  • •C50.521: Lower-outer quadrant of right male breast; wrong gender code: verify patient sex
  • •C50.512: Lower-outer quadrant of left female breast; laterality error: confirm right vs. left
  • •C50.911: Unspecified site of right female breast; less specific when quadrant is actually documented

Child Codes

C50.511Malignant neoplasm of lower-outer quadrant of right female breast
HCC 22
C50.512Malignant neoplasm of lower-outer quadrant of left female breast
HCC 22
C50.519Malignant neoplasm of lower-outer quadrant of unspecified female breast
HCC 22

Code Hierarchy

└C50Malignant neoplasm of breast└C50.5Malignant neoplasm of lower-outer quadrant of breast└C50.51Malignant neoplasm of lower-outer quadrant of breast, female└C50.511Malignant neoplasm of lower-outer quadrant of right female breast
└C50.511Malignant neoplasm of lower-outer quadrant of right female breast

For C50.511, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

C50.511 maps to CMS-HCC V28 category 23, Prostate, Breast, and Other Cancers and Tumors. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for C50.511. Review its source-labeled HCC coefficient above, check the RAF Calculator with complete member context for CMS-HCC V28 PY2026, and confirm the documentation the chart needs before the code is submitted. HCC Buddy shows no RAF score unless every required source and calculation check passes.

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