C50.422 ICD-10-CM Code: Malignant neoplasm of upper-outer quadrant of left male breast
HCC Buddy Code Card
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FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of breast (C50)
C50.422
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceMalignant neoplasm of upper-outer quadrant of left male breast
Cancer that develops in the upper-outer area of the left breast in men. Male breast cancer is uncommon but requires specific coding.
Buddy Insight
Male breast cancer of the upper-outer quadrant of the left breast is a rare malignancy accounting for less than 1% of all breast cancers.
CMS-HCC V28
00
RAF 0
CMS-HCC V24
MappedHCC 12
RAF 0.150
ACA/HHS
00
RAF 0
ESRD/PACE
MappedHCC 12
RAF 0.0
RXHCC
MappedHCC 22
RAF 0.0
Code Trumping
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Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for C50.422 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for C50.422 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for C50.422 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for C50.422 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for C50.422 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for C50.422 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for C50.422 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is C50.422 an HCC code?
Yes. C50.422 maps to Breast, Prostate, and Other Cancers and Tumors under the V24 model but is not retained in V28.
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for C50.422
For C50.422to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.
- 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
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed C50.422 during that encounter, not just copy-forwarded from a problem list.
What This Code Means
C50.422 is the ICD-10-CM diagnosis code for malignant neoplasm of upper-outer quadrant of left male breast. Cancer that develops in the upper-outer area of the left breast in men. Male breast cancer is uncommon but requires specific coding. C50.422 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of breast (c50).
Under the older CMS-HCC V24 model, C50.422 maps to Breast, Prostate, and Other Cancers and Tumors (HCC 12) with a community, non-dual, aged base RAF weight of 0.150. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Verify male gender and left breast location in the documentation. Because C50.422 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. 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, RAF weights, and MEAT documentation criteria for C50.422 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify male gender and left breast location in the documentation
- •Remember that male breast cancer codes differ from female codes in the 4th digit position
Clinical Significance
Male breast cancer of the upper-outer quadrant of the left breast is a rare malignancy accounting for less than 1% of all breast cancers. Accurate site and laterality documentation is critical for staging, surgical planning, and risk adjustment, as male breast cancers often present at later stages due to delayed detection.
Documentation Requirements
- ✓Confirmed male patient sex
- ✓Laterality documented as left breast
- ✓Specific quadrant identified as upper-outer
- ✓Histological type (invasive ductal carcinoma is most common in males)
- ✓Tumor stage (TNM classification)
- ✓Receptor status (estrogen receptor, progesterone receptor, HER2) when available
- ✓Current treatment status (active treatment, surveillance, or history of)
Commonly Confused Codes
- •C50.412 — Malignant neoplasm of upper-outer quadrant of left female breast; coders confuse the 4th character (1=female, 2=male) which drives gender-specific coding
- •C50.429 — Malignant neoplasm of upper-outer quadrant of unspecified male breast; used only when laterality is unknown, but coders default to unspecified instead of querying
- •C50.922 — Malignant neoplasm of unspecified site of left male breast; less specific site designation when the quadrant is actually documented