C13.8
BillableMalignant neoplasm of overlapping sites of hypopharynx
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C13.8 an HCC code?
Yes. C13.8 maps to Lymphoma and Other Cancers 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 C13.8
For C13.8to 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 C13.8 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C13.8 is the ICD-10-CM diagnosis code for malignant neoplasm of overlapping sites of hypopharynx. Cancer that involves multiple overlapping sites within the hypopharynx, the lower part of the throat. C13.8 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, C13.8 maps to Lymphoma and Other Cancers (HCC 21) with a community, non-dual, aged base RAF weight of 0.671. Under the older CMS-HCC V24 model, C13.8 maps to Colorectal, Bladder, and Other Cancers (HCC 11) with a community, non-dual, aged base RAF weight of 0.307. 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.
Use this code when the tumor spans more than one hypopharyngeal site without a single primary location. Because C13.8 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 C13.8 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code when the tumor spans more than one hypopharyngeal site without a single primary location
- •Document all involved sites in the medical record for treatment planning purposes
Clinical Significance
This overlapping sites code represents hypopharyngeal cancer involving multiple subsites (pyriform sinus, postcricoid region, posterior wall, aryepiglottic fold) where a single primary origin cannot be determined. These are typically advanced cancers with poorer prognosis than single-site hypopharyngeal tumors.
Documentation Requirements
- ✓Imaging and endoscopy documenting involvement of multiple hypopharyngeal subsites
- ✓Documentation of which specific hypopharyngeal structures are involved
- ✓Evidence that a single primary subsite cannot be identified
- ✓Complete TNM staging reflecting the multi-site extent
- ✓Assessment of laryngeal involvement and vocal cord function
Commonly Confused Codes
- •C13.9 — Hypopharynx, unspecified; use when the subsite is unknown, not when multiple sites are known
- •C12 — Pyriform sinus; use when tumor is confined to the pyriform sinus
- •C14.8 — Overlapping sites of lip, oral cavity and pharynx; use when tumor extends beyond hypopharynx
- •C13.0-C13.2 — Specific hypopharyngeal subsites; use when a single primary site is identifiable