C50.429 ICD-10-CM Code: Malignant neoplasm of upper-outer quadrant of unspecified male breast
C50.429 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 · HCC coding software
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FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of breast (C50)
C50.429
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceMalignant neoplasm of upper-outer quadrant of unspecified male breast
Cancer in the upper-outer area of the breast in men when the specific side is not documented or cannot be determined.
Buddy Insight
This unspecified laterality code for male breast cancer of the upper-outer quadrant should be a red flag for incomplete documentation.
CMS-HCC V28
MappedHCC 23
Coefficient HCC 23: 0.186 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
Context neededHCC 011, HCC 012
Coefficient needs member context
ESRD/PACE
Context neededHCC 12
Coefficient needs member context
RXHCC
MappedHCC 22
Code-level coefficient reference
Code Book Path
Inclusion Terms
OfficialNo inclusion terms are included in this display for C50.429. Check the code and parent instructions in the Code Book.
Excludes 2
OfficialNo Excludes 2 notes are included in this display for C50.429. Check the code and parent instructions in the Code Book.
Related Codes
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
OfficialNo Code First sequencing instructions are included in this display for C50.429. 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
OfficialNo Code Also instructions are included in this display for C50.429. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
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 C50.429 an HCC code?
Yes. C50.429 (Malignant neoplasm of upper-outer quadrant of unspecified male 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: C50.429 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
- C50.429
- Description
- Malignant neoplasm of upper-outer quadrant of unspecified male 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
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 C50.429 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for C50.429
For C50.429, 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
C50.429 is the ICD-10-CM diagnosis code for malignant neoplasm of upper-outer quadrant of unspecified male breast. Cancer in the upper-outer area of the breast in men when the specific side is not documented or cannot be determined. C50.429 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, C50.429 maps to Prostate, Breast, and Other Cancers and Tumors (HCC 23) with a source-labeled community, non-dual, aged reference coefficient of 0.186. 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.
This unspecified code should be used only when laterality is truly unknown. For C50.429, 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 C50.429 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This unspecified code should be used only when laterality is truly unknown
- •Attempt to clarify laterality through provider query or review of imaging reports
Clinical Significance
This unspecified laterality code for male breast cancer of the upper-outer quadrant should be a red flag for incomplete documentation. Male breast cancer requires precise anatomical coding for treatment planning and cancer registry reporting. Using an unspecified code misses the opportunity for accurate risk stratification.
Documentation Requirements
- ✓Confirmed male patient sex
- ✓Clinical explanation for why laterality cannot be determined
- ✓Quadrant confirmed as upper-outer
- ✓Histological type and grade
- ✓Staging information
- ✓Evidence of provider query attempt for laterality clarification