C03.1
BillableMalignant neoplasm of lower gum
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C03.1 an HCC code?
Yes. C03.1 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 C03.1
For C03.1 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 C03.1 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C03.1 is the ICD-10-CM diagnosis code for malignant neoplasm of lower gum. Cancer that starts in the lower gum tissue, typically involving the tissue covering the lower jaw bone. C03.1 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, C03.1 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, C03.1 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.
Verify laterality if documented (left vs right lower gum). Because C03.1 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 C03.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
Clinical Significance
Malignant neoplasm of the lower gum involves cancer of the mandibular gingiva. Lower gum cancers are more common than upper gum cancers and frequently invade the mandibular bone, often requiring more extensive surgical intervention including mandibulectomy.
Documentation Requirements
- ✓Pathology-confirmed malignancy with histological type (typically squamous cell carcinoma)
- ✓Specific site documented as lower gum or mandibular gingiva
- ✓TNM staging with depth of invasion, particularly bone involvement
- ✓Laterality if documented (left vs right mandibular gingiva)
- ✓Treatment plan and current status (active, remission, or surveillance)
Commonly Confused Codes
- •C03.0 — Malignant neoplasm of upper gum; ensure documentation specifies mandibular (lower) not maxillary (upper) gingiva
- •C03.9 — Malignant neoplasm of gum, unspecified; avoid when lower gum is clearly documented
- •C41.1 — Malignant neoplasm of mandible; use when cancer originates in bone rather than overlying gum tissue
- •C04.0 — Malignant neoplasm of anterior floor of mouth; adjacent site that may overlap with lower gum tumors