C43.10
BillableMalignant melanoma of unspecified eyelid, including canthus
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C43.10 an HCC code?
Yes. C43.10 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 C43.10
For C43.10 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 C43.10 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C43.10 is the ICD-10-CM diagnosis code for malignant melanoma of unspecified eyelid, including canthus. Melanoma (a serious type of skin cancer) of the eyelid when the specific eye is not identified. C43.10 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering melanoma and other malignant neoplasms of skin (c43-c44).
Under the CMS-HCC V28 risk adjustment model, C43.10 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, C43.10 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.
Eyelid melanoma is relatively rare; ensure documentation clearly indicates eyelid location. Because C43.10 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 C43.10 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Eyelid melanoma is relatively rare; ensure documentation clearly indicates eyelid location
- •Query for laterality (right or left eye) to assign a more specific code if available
Clinical Significance
Malignant melanoma of the eyelid, including the canthus, with unspecified laterality. Eyelid melanomas are rare but important because of their proximity to the eye and potential for orbital and intracranial spread. Mohs micrographic surgery or wide excision with margin control is typically required. The unspecified laterality should prompt a provider query.
Documentation Requirements
- ✓Attempt to clarify laterality (right vs. left) and specific eyelid (upper vs. lower)
- ✓Breslow depth and Clark level
- ✓Whether the canthus (inner or outer corner) is involved
- ✓Ulceration status and mitotic rate
- ✓Sentinel lymph node biopsy results (parotid and cervical nodes)
- ✓AJCC staging