C50.919
BillableMalignant neoplasm of unspecified site of unspecified female breast
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C50.919 an HCC code?
Yes. C50.919 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 C50.919
For C50.919 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 C50.919 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C50.919 is the ICD-10-CM diagnosis code for malignant neoplasm of unspecified site of unspecified female breast. This code represents cancer of the breast in a woman, but the specific location within the breast and which breast (left or right) has not been documented or specified. This is used when there is insufficient information to identify the exact site of the tumor. C50.919 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, C50.919 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, C50.919 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.
Avoid using this code when more specific information is available; always query the provider for laterality (left vs. right breast) and specific quadrant or site of the malignancy, as more specific codes provide better clinical data. Because C50.919 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 C50.919 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Avoid using this code when more specific information is available; always query the provider for laterality (left vs. right breast) and specific quadrant or site of the malignancy, as more specific codes provide better clinical data
- •This unspecified code should rarely be used in current practice due to ICD-10-CM requirements for laterality; ensure documentation clearly indicates why the site cannot be determined before assigning this code
Clinical Significance
This is the least specific female breast cancer code, lacking both site and laterality information. In modern oncology practice, this code should be extremely rare because imaging, pathology, and clinical examination virtually always establish at minimum the laterality of a breast cancer. High usage rates of this code suggest systemic documentation or coding process issues.
Documentation Requirements
- ✓Confirmed female patient sex
- ✓Confirmed active breast cancer diagnosis
- ✓Documentation explaining why neither laterality nor site can be determined
- ✓Evidence that all available records (imaging, pathology, surgical notes) were reviewed
- ✓Evidence of provider query for laterality and site specification
Commonly Confused Codes
- •C50.911 — Unspecified site of right female breast; use when right laterality is confirmed
- •C50.912 — Unspecified site of left female breast; use when left laterality is confirmed
- •C50.819 — Overlapping sites of unspecified female breast; different designation for multifocal disease
- •Z85.3 — Personal history of breast cancer; use when cancer is no longer active