C7B.1 ICD-10-CM Code: Secondary Merkel cell carcinoma
HCC Buddy Code Card
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FY 2026 Apr update / Neoplasms (C00-D49) / Secondary neuroendocrine tumors (C7B)
C7B.1
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceSecondary Merkel cell carcinoma
Merkel cell carcinoma (a rare skin cancer) that has spread to other parts of the body from its original location.
Buddy Insight
Secondary Merkel cell carcinoma indicates that Merkel cell carcinoma, a rare and aggressive neuroendocrine skin cancer, has metastasized to other body sites.
CMS-HCC V28
MappedHCC 17
RAF 4.209
CMS-HCC V24
MappedHCC 8
RAF 2.659
ACA/HHS
MappedHCC 8
Varies by metal level
ESRD/PACE
MappedHCC 8
RAF 0.353
RXHCC
MappedHCC 18
RAF 1.949
Code Book Path
Inclusion Terms
Official- Merkel cell carcinoma nodal presentation
- Merkel cell carcinoma visceral metastatic presentation
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for C7B.1 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for C7B.1 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for C7B.1 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for C7B.1 in this effective period.
Use Additional
Official- code to identify any functional activity
Code Also
OfficialICD-10-CM does not list Code Also instructions for C7B.1 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is C7B.1 an HCC code?
Yes. C7B.1 (Secondary Merkel cell carcinoma) maps to Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic under the CMS-HCC V28 risk adjustment model (and Metastatic Cancer and Acute Leukemia under V24), with a community non-dual aged RAF of 4.209. It is billable for payment year 2026.
Coder answer: C7B.1 is billable and maps to V28 HCC 17, Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- C7B.1
- Description
- Secondary Merkel cell carcinoma
- HCC (V28)
- HCC 17 — Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic
- RAF
- 4.209
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. 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.
Work C7B.1 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
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.
Coder workflow notes
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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 Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic (HCC 17) with a community, non-dual, aged base RAF weight of 4.209. Under the older CMS-HCC V24 model, C7B.1 maps to Metastatic Cancer and Acute Leukemia (HCC 8) with a community, non-dual, aged base RAF weight of 2.659. 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