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C13.8 ICD-10-CM Code: Malignant neoplasm of overlapping sites of hypopharynx

C13.8 maps to CMS-HCC V28 21. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · free HCC coding tools

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Code lookupC13.8

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of lip, oral cavity and pharynx (C00-C14)

C13.8

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Malignant neoplasm of overlapping sites of hypopharynx

Cancer that involves multiple overlapping sites within the hypopharynx, the lower part of the throat.

Buddy the Bee presenting code insight

Buddy Insight

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.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 21

Coefficient HCC 21: 0.671 (Community Non-Dual Aged (CNA))

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 011

Code-level coefficient reference

ESRD/PACE

HCC 11

Code-level coefficient reference

RXHCC

N/A

—

Not mapped

Code Book Path

Official
C13Malignant neoplasm of hypopharynxC13.8Malignant neoplasm of overlapping sites of hypopharynx

Inclusion Terms

Official

No inclusion terms are included in this display for C13.8. Check the code and parent instructions in the Code Book.

Excludes 2

Official
  • malignant neoplasm of pyriform sinus (C12)Inherited from C13

Related Codes

Official
C13.0Malignant neoplasm of postcricoid regionC13.1Malignant neoplasm of aryepiglottic fold, hypopharyngeal aspectC13.2Malignant neoplasm of posterior wall of hypopharynxC13.9Malignant neoplasm of hypopharynx, unspecified

Includes

Official

No Includes notes are included in this display for C13.8. Check the code and parent instructions in the Code Book.

Excludes 1

Official

No Excludes 1 notes are included in this display for C13.8. Check the code and parent instructions in the Code Book.

Code First

Official

No Code First sequencing instructions are included in this display for C13.8. Check the code and parent instructions in the Code Book.

Use Additional

Official
  • code to identify:Inherited from C13
  • exposure to environmental tobacco smoke (Z77.22)Inherited from C13
  • exposure to tobacco smoke in the perinatal period (P96.81)Inherited from C13
  • history of tobacco dependence (Z87.891)Inherited from C13
  • occupational exposure to environmental tobacco smoke (Z57.31)Inherited from C13
  • tobacco dependence (F17.-)Inherited from C13
  • tobacco use (Z72.0)Inherited from C13

Code Also

Official

No Code Also instructions are included in this display for C13.8. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
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

MEAT Support

HCC Buddy guidance
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

Audit Caution

HCC Buddy guidance
Confusing overlapping (multiple known subsites) with unspecified (unknown subsite)
Using this code when the tumor clearly originates in one subsite with minor extension to adjacent areas
Not documenting which specific hypopharyngeal subsites are involved in the overlap
Failing to use C14.8 when the tumor extends beyond the hypopharynx into the oropharynx or esophagus

Common Mistakes

HCC Buddy guidance
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

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is C13.8 an HCC code?

Yes. C13.8 (Malignant neoplasm of overlapping sites of hypopharynx) maps to HCC 21, Lymphoma and Other Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.671. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: C13.8 is billable and maps to V28 HCC 21, Lymphoma and Other Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
C13.8
Description
Malignant neoplasm of overlapping sites of hypopharynx
HCC (V28)
HCC 21 — Lymphoma and Other Cancers
RAF reference coefficient
0.671
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 21, Lymphoma and Other Cancers
0.671
ESRDHCC 11, Colorectal/Bladder/and Other Cancers
Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. 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 context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work C13.8 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C13.8

For C13.8, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

  • 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

Coder workflow notes

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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 source-labeled community, non-dual, aged reference coefficient of 0.671. No V24 mapping is shown for C13.8; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

Use this code when the tumor spans more than one hypopharyngeal site without a single primary location. For C13.8, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, 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

Child Codes

C13.0Malignant neoplasm of postcricoid region
HCC 21
C13.1Malignant neoplasm of aryepiglottic fold, hypopharyngeal aspect
HCC 21
C13.2Malignant neoplasm of posterior wall of hypopharynx
HCC 21
C13.8Malignant neoplasm of overlapping sites of hypopharynx
HCC 21
C13.9Malignant neoplasm of hypopharynx, unspecified
HCC 21

Code Hierarchy

└C13Malignant neoplasm of hypopharynx└C13.8Malignant neoplasm of overlapping sites of hypopharynx
└C13.8Malignant neoplasm of overlapping sites of hypopharynx

Also searched as

  • C13 8
  • C138

For C13.8, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

C13.8 maps to CMS-HCC V28 category 21, Lymphoma and Other Cancers. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for C13.8. Review its source-labeled HCC coefficient above, check the RAF Calculator with complete member context for CMS-HCC V28 PY2026, and confirm the documentation the chart needs before the code is submitted. HCC Buddy shows no RAF score unless every required source and calculation check passes.

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