C7A.1
BillableMalignant poorly differentiated neuroendocrine tumors
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C7A.1 an HCC code?
Yes. C7A.1 maps to Breast, Prostate, Colorectal and Other Cancers and Tumors 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 C7A.1
For C7A.1 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 C7A.1 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C7A.1 is the ICD-10-CM diagnosis code for malignant poorly differentiated neuroendocrine tumors. A rare, aggressive cancer of hormone-producing cells that appear abnormal under the microscope and do not have well-defined characteristics. C7A.1 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neuroendocrine tumors (c7a).
Under the CMS-HCC V28 risk adjustment model, C7A.1 maps to Breast, Prostate, Colorectal and Other Cancers and Tumors (HCC 21) with a community, non-dual, aged base RAF weight of 0.545. Under the older CMS-HCC V24 model, C7A.1 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.
Poorly differentiated neuroendocrine tumors have worse prognosis; ensure pathology confirms poor differentiation grade. Because C7A.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 C7A.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Poorly differentiated neuroendocrine tumors have worse prognosis; ensure pathology confirms poor differentiation grade
- •Document the primary site separately if known, as this code focuses on differentiation level rather than location
Clinical Significance
Malignant poorly differentiated neuroendocrine tumors represent high-grade, aggressive neuroendocrine carcinomas with poor cellular differentiation on pathology. These tumors behave similarly to small cell carcinoma and carry a significantly worse prognosis than well-differentiated carcinoid tumors. They are typically fast-growing, have high mitotic rates (Ki-67 greater than 20%), and frequently present with advanced or metastatic disease requiring aggressive chemotherapy regimens.
Documentation Requirements
- ✓Pathology report confirming poorly differentiated/high-grade neuroendocrine histology (Grade 3)
- ✓Ki-67 proliferation index (typically greater than 20%)
- ✓Primary site of origin if known (code the primary site separately)
- ✓Small cell versus large cell neuroendocrine carcinoma distinction
- ✓Stage at diagnosis including metastatic workup
- ✓Treatment regimen (typically platinum-based chemotherapy similar to small cell lung cancer)
Commonly Confused Codes
- •C7A.0 series — Site-specific malignant carcinoid tumors: Carcinoids are typically well-differentiated (G1-G2); C7A.1 is for poorly differentiated (G3) neuroendocrine tumors
- •C34.90 — Malignant neoplasm of bronchus/lung: Small cell lung cancer is a form of poorly differentiated neuroendocrine carcinoma but has its own specific code
- •C7A.8 — Other malignant neuroendocrine tumors: Use C7A.8 for neuroendocrine tumors that don't fit carcinoid or poorly differentiated categories