C50.621
BillableMalignant neoplasm of axillary tail of right male breast
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C50.621 an HCC code?
Yes. C50.621 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 C50.621
For C50.621 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 C50.621 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C50.621 is the ICD-10-CM diagnosis code for malignant neoplasm of axillary tail of right male breast. Cancer that develops in the axillary tail (the extension of breast tissue toward the armpit) of the right male breast. C50.621 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, C50.621 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, C50.621 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.
Male breast cancer is rare; ensure documentation clearly indicates male patient and right-sided location. Because C50.621 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 C50.621 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Male breast cancer is rare; ensure documentation clearly indicates male patient and right-sided location
- •The axillary tail location may have implications for lymph node involvement assessment
Clinical Significance
Cancer of the axillary tail of the right male breast is extremely rare, combining the rarity of male breast cancer with a less common anatomical location. The axillary tail location in males warrants careful assessment for lymph node involvement given the proximity to axillary lymphatic drainage and the typically later-stage presentation in male patients.
Documentation Requirements
- ✓Confirmed male patient sex
- ✓Laterality documented as right breast
- ✓Specific site identified as axillary tail
- ✓Histological type and grade
- ✓Lymph node status
- ✓TNM staging
- ✓BRCA or other genetic testing results if performed