C50.519
BillableMalignant neoplasm of lower-outer quadrant of unspecified female breast
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C50.519 an HCC code?
Yes. C50.519 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 C50.519
For C50.519 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 C50.519 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C50.519 is the ICD-10-CM diagnosis code for malignant neoplasm of lower-outer quadrant of unspecified female breast. Cancer in the lower-outer area of the breast in women when the specific side (left or right) is not documented. C50.519 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, C50.519 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, C50.519 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.
Use only when laterality is genuinely unspecified in the medical record. Because C50.519 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 C50.519 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use only when laterality is genuinely unspecified in the medical record
- •Check operative reports, imaging studies, and pathology reports for laterality information
Clinical Significance
This unspecified laterality code for female breast cancer of the lower-outer quadrant indicates a documentation gap. In modern oncology practice, laterality should virtually always be determinable from imaging, pathology, or surgical records. This code should be used sparingly and prompts a provider query.
Documentation Requirements
- ✓Confirmed female patient sex
- ✓Quadrant confirmed as lower-outer
- ✓Clinical rationale for why laterality cannot be determined
- ✓Evidence that provider query was attempted for laterality clarification
- ✓Histological type and staging information