C7B.1
BillableSecondary Merkel cell carcinoma
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C7B.1 an HCC code?
Yes. C7B.1 maps to Metastatic Cancer and Acute Leukemia under the CMS-HCC V28 risk adjustment model (and Metastatic Cancer and Acute Leukemia 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 C7B.1
For C7B.1to 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 C7B.1 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C7B.1 is the ICD-10-CM diagnosis code for secondary merkel cell carcinoma. Merkel cell carcinoma (a rare skin cancer) that has spread to other parts of the body from its original location. C7B.1 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering secondary neuroendocrine tumors (c7b).
Under the CMS-HCC V28 risk adjustment model, C7B.1 maps to Metastatic Cancer and Acute Leukemia (HCC 17) with a community, non-dual, aged base RAF weight of 0.368. Under the older V24 model, C7B.1 mapped to the same category but with a base RAF weight of 2.484 — V28 recalibrated weights across the entire model. 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 indicates metastatic disease; code the primary Merkel cell carcinoma site separately. Because C7B.1 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 C7B.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code indicates metastatic disease; code the primary Merkel cell carcinoma site separately
- •Document the site of metastasis in addition to this code for complete clinical picture
Clinical Significance
Secondary Merkel cell carcinoma indicates that Merkel cell carcinoma, a rare and aggressive neuroendocrine skin cancer, has metastasized to other body sites. Merkel cell carcinoma has a higher mortality rate than melanoma, and metastatic disease carries a very poor prognosis with 5-year survival rates below 20%. It is most common in elderly and immunocompromised patients and is associated with Merkel cell polyomavirus infection.
Documentation Requirements
- ✓Pathology confirming Merkel cell carcinoma histology (CK20 positive, TTF-1 negative on immunohistochemistry)
- ✓Primary Merkel cell carcinoma site documented and coded separately (C4A codes)
- ✓Specific site(s) of metastasis documented
- ✓Immunocompromised status if present (HIV, transplant, chronic immunosuppression)
- ✓PD-L1 expression and Merkel cell polyomavirus status if tested
- ✓Treatment plan (immunotherapy with checkpoint inhibitors, chemotherapy, radiation)
Commonly Confused Codes
- •C4A series — Merkel cell carcinoma, primary site: Use C4A codes for the primary skin tumor site; C7B.1 is for metastatic disease only
- •C7B.8 — Other secondary neuroendocrine tumors: Use C7B.8 for non-Merkel, non-carcinoid metastatic neuroendocrine tumors
- •C79.2 — Secondary malignant neoplasm of skin: Use for non-neuroendocrine cancer metastatic to skin
- •C43 series — Malignant melanoma: Both are aggressive skin cancers but have completely different histology and coding