C50.321
BillableMalignant neoplasm of lower-inner quadrant of right male breast
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C50.321 an HCC code?
Yes. C50.321 maps to Melanoma and Other Skin Cancers under the CMS-HCC V28 risk adjustment model (and Breast, Prostate, and Other Cancers and Tumors under V24).
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 C50.321
For C50.321 to 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 C50.321 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C50.321 is the ICD-10-CM diagnosis code for malignant neoplasm of lower-inner quadrant of right male breast. Cancer that starts in the lower-inner area of the right breast in a male patient. C50.321 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, C50.321 maps to Melanoma and Other Skin Cancers (HCC 23) with a community, non-dual, aged base RAF weight of 0.251. Under the older CMS-HCC V24 model, C50.321 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 both the quadrant location (lower-inner) and laterality (right) are clearly documented. Because C50.321 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 C50.321 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify both the quadrant location (lower-inner) and laterality (right) are clearly documented
- •Male breast cancer in the lower-inner quadrant is rare; ensure documentation accuracy
Clinical Significance
Malignant neoplasm of the lower-inner quadrant of right male breast represents invasive breast cancer requiring staging, treatment planning, and ongoing surveillance. Breast cancer is risk-adjusted because it demands significant healthcare resources including surgery, radiation, chemotherapy, hormonal therapy, and long-term monitoring. Male breast cancer accounts for less than 1% of all breast cancers, making accurate gender-specific coding particularly important for tracking and research.
Documentation Requirements
- ✓Pathologic confirmation of invasive malignancy (biopsy with histologic type — ductal, lobular, etc.)
- ✓Laterality: right breast
- ✓Gender documented as male to support gender-specific code selection
- ✓Quadrant or subsite location: lower-inner quadrant
- ✓Tumor size (T stage) and grade
- ✓Lymph node status (N stage) — axillary, sentinel node biopsy results
- ✓Estrogen receptor, progesterone receptor, and HER2 status
- ✓Stage grouping (I-IV)
- ✓Current treatment status (active treatment, hormonal therapy, surveillance)
Commonly Confused Codes
- •C50.322 — Lower-inner quadrant of left male breast; verify laterality
- •C50.329 — Lower-inner quadrant unspecified male; use only when laterality unknown
- •C50.311 — Same laterality but female breast; verify patient gender
- •C50.221-C50.229 — Upper-inner quadrant of male breast; same medial orientation, different vertical position
- •C50.121-C50.129 — Central portion of male breast; adjacent but distinct subsite
- •N62 — Gynecomastia; benign condition, not malignant