D03.51
BillableMelanoma in situ of anal skin
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is D03.51 an HCC code?
Yes. D03.51 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 D03.51
For D03.51 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 D03.51 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
D03.51 is the ICD-10-CM diagnosis code for melanoma in situ of anal skin. Early-stage melanoma confined to the skin surface in the anal area, before it has invaded deeper layers of tissue. D03.51 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, D03.51 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, D03.51 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.
Anal melanomas are rare but have significant clinical implications; ensure documentation clearly identifies this location. Because D03.51 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 D03.51 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Anal melanomas are rare but have significant clinical implications; ensure documentation clearly identifies this location
- •This specific site requires careful staging and treatment planning due to anatomical considerations
Clinical Significance
Melanoma in situ of the anal skin is a rare non-invasive melanocytic neoplasm confined to the epidermis of the perianal region. Anal melanoma is uncommon but clinically significant because the anal region is not typically associated with melanoma, leading to potential diagnostic delays. Early detection at the in situ stage offers excellent prognosis, but the anatomical location requires specialized surgical approaches.
Documentation Requirements
- ✓Biopsy confirmation with pathology documenting atypical melanocytes confined to the epidermis of the anal skin.
- ✓The exact location relative to the anal verge (perianal skin vs.
- ✓anal margin vs.
- ✓anal canal) must be documented, as anal canal melanoma is classified differently.
- ✓Include margin status and surveillance plan.