C10.4
BillableMalignant neoplasm of branchial cleft
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C10.4 an HCC code?
Yes. C10.4 maps to Breast, Prostate, Colorectal and Other Cancers and Tumors under the CMS-HCC V28 risk adjustment model (and Colorectal, Bladder, and Other Cancers 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 C10.4
For C10.4 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 C10.4 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C10.4 is the ICD-10-CM diagnosis code for malignant neoplasm of branchial cleft. Cancer arising from a branchial cleft, which is a remnant of embryonic tissue in the neck that can develop into a cyst or tumor. C10.4 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of lip, oral cavity and pharynx (c00-c14).
Under the CMS-HCC V28 risk adjustment model, C10.4 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, C10.4 maps to Colorectal, Bladder, and Other Cancers (HCC 11) with a community, non-dual, aged base RAF weight of 0.306. 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.
Branchial cleft cancers are rare and typically arise from branchial cleft cysts that have undergone malignant transformation. Because C10.4 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 C10.4 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Branchial cleft cancers are rare and typically arise from branchial cleft cysts that have undergone malignant transformation
- •Verify that pathology confirms malignancy arising from branchial cleft tissue rather than primary oropharyngeal cancer
Clinical Significance
Malignant neoplasm of the branchial cleft is a rare tumor arising from embryonic remnant tissue in the neck. Branchial cleft carcinomas are controversial in oncology — some experts question whether primary branchial cleft carcinomas exist at all, arguing that most represent cystic metastases from occult oropharyngeal primaries, particularly HPV-related tumors.
Documentation Requirements
- ✓Pathology confirming malignancy arising from branchial cleft tissue
- ✓Exclusion of occult primary oropharyngeal cancer (particularly HPV-related tonsillar or tongue base cancer)
- ✓HPV/p16 testing of the tumor specimen
- ✓Documentation of complete head and neck evaluation including PET/CT or MRI to rule out other primary sites
- ✓Laterality and relationship to sternocleidomastoid muscle and great vessels