D03.121
BillableMelanoma in situ of left upper eyelid, including canthus
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is D03.121 an HCC code?
Yes. D03.121 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 D03.121
For D03.121 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 D03.121 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
D03.121 is the ICD-10-CM diagnosis code for melanoma in situ of left upper eyelid, including canthus. Abnormal melanoma cells on the left upper eyelid or corner of the left eye that have not yet invaded deeper tissue. D03.121 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering in situ neoplasms (d00-d09).
Under the CMS-HCC V28 risk adjustment model, D03.121 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, D03.121 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.
This code specifies the left upper eyelid - confirm documentation indicates left side and upper eyelid location. Because D03.121 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 D03.121 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code specifies the left upper eyelid - confirm documentation indicates left side and upper eyelid location
- •Distinguish from D03.122 which codes the left lower eyelid
Clinical Significance
Melanoma in situ of the left upper eyelid is a non-invasive melanocytic neoplasm confined to the epidermal layer of the left upper eyelid or adjacent left canthal area. Upper eyelid melanoma in situ can be particularly challenging to detect due to partial concealment by the brow and eyelid fold. Early biopsy of any new or changing pigmented lesion in this area is critical for timely diagnosis.
Documentation Requirements
- ✓Pathology must confirm melanoma in situ with no dermal invasion.
- ✓Left laterality and upper eyelid location must be explicitly documented.
- ✓Include the dimensions of the lesion, dermoscopic findings, and whether the medial or lateral canthus is involved for comprehensive clinical documentation.