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D42.9 ICD-10-CM Code: Neoplasm of uncertain behavior of meninges, unspecified

D42.9 maps to CMS-HCC V28 23. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC Buddy coding tools

ICD-10-CM Code View

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Code lookupD42.9

FY 2026 Apr update / Neoplasms (C00-D49) / Neoplasms of uncertain behavior, polycythemia vera and myelodysplastic syndromes (D37-D48)

D42.9

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

Neoplasm of uncertain behavior of meninges, unspecified

A growth in the membrane surrounding the brain or spinal cord that cannot yet be classified as definitely cancer or definitely benign, but the exact location is not specified.

Buddy the Bee presenting code insight

Buddy Insight

This unspecified code represents a meningeal tumor of uncertain behavior when the location (cerebral versus spinal) cannot be determined.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 23

Coefficient HCC 23: 0.186 (Community Non-Dual Aged (CNA))

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 012

Code-level coefficient reference

ESRD/PACE

HCC 12

Code-level coefficient reference

RXHCC

HCC 22

Code-level coefficient reference

Code Book Path

Official
D42Neoplasm of uncertain behavior of meningesD42.9Neoplasm of uncertain behavior of meninges, unspecified

Inclusion Terms

Official

No inclusion terms are included in this display for D42.9. Check the code and parent instructions in the Code Book.

Excludes 2

Official

No Excludes 2 notes are included in this display for D42.9. Check the code and parent instructions in the Code Book.

Related Codes

Official
D42.0Neoplasm of uncertain behavior of cerebral meningesD42.1Neoplasm of uncertain behavior of spinal meninges

Includes

Official

No Includes notes are included in this display for D42.9. Check the code and parent instructions in the Code Book.

Excludes 1

Official
  • neoplasms of unspecified behavior (D49.-)Inherited from D37-D48

Code First

Official

No Code First sequencing instructions are included in this display for D42.9. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for D42.9. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for D42.9. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
This code should only be used when documentation does not differentiate between cerebral and spinal meningeal involvement.
A provider query is strongly recommended to determine the specific location from imaging, operative notes, or pathology reports.
Pathology should confirm uncertain behavior classification.

MEAT Support

HCC Buddy guidance
This code should only be used when documentation does not differentiate between cerebral and spinal meningeal involvement.
A provider query is strongly recommended to determine the specific location from imaging, operative notes, or pathology reports.
Pathology should confirm uncertain behavior classification.

Audit Caution

HCC Buddy guidance
Always query the provider for anatomical specificity before defaulting to this unspecified code.
Imaging reports (magnetic resonance imaging or computed tomography) typically specify the meningeal tumor location and should be reviewed.
Unspecified codes may trigger payer audits and reduce documentation quality scores.

Common Mistakes

HCC Buddy guidance
D42.0 (cerebral meninges) and D42.1 (spinal meninges) are the site-specific alternatives and should be used whenever the location is documented.
D32.9 (benign meningioma, unspecified) is used for confirmed benign tumors.
C70.9 (malignant neoplasm of meninges, unspecified) is the malignant counterpart.

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 D42.9 an HCC code?

Yes. D42.9 (Neoplasm of uncertain behavior of meninges, unspecified) maps to HCC 23, Prostate, Breast, and Other Cancers and Tumors under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.186. 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: D42.9 is billable and maps to V28 HCC 23, Prostate, Breast, and Other Cancers and Tumors. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
D42.9
Description
Neoplasm of uncertain behavior of meninges, unspecified
HCC (V28)
HCC 23 — Prostate, Breast, and Other Cancers and Tumors
RAF reference coefficient
0.186
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 23, Prostate, Breast, and Other Cancers and Tumors
0.186
ESRDHCC 12, Breast/Prostate/and Other Cancers and Tumors
Not separately weighted
RxHCCHCC 22, Prostate, Breast, Bladder, and Other Cancers and Tumors
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 D42.9 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for D42.9

For D42.9, 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

D42.9 is the ICD-10-CM diagnosis code for neoplasm of uncertain behavior of meninges, unspecified. A growth in the membrane surrounding the brain or spinal cord that cannot yet be classified as definitely cancer or definitely benign, but the exact location is not specified. D42.9 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering neoplasms of uncertain behavior, polycythemia vera and myelodysplastic syndromes (d37-d48).

Under the CMS-HCC V28 risk adjustment model, D42.9 maps to Prostate, Breast, and Other Cancers and Tumors (HCC 23) with a source-labeled community, non-dual, aged reference coefficient of 0.186. No V24 mapping is shown for D42.9; 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 only when it cannot be determined whether the meningeal lesion is cerebral or spinal. For D42.9, 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 D42.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Use this code only when it cannot be determined whether the meningeal lesion is cerebral or spinal
  • •Query the provider if possible to obtain specific anatomical location (brain vs. spinal cord) for more precise coding

Clinical Significance

This unspecified code represents a meningeal tumor of uncertain behavior when the location (cerebral versus spinal) cannot be determined. Using this code limits clinical utility because treatment and prognosis differ significantly based on whether the tumor involves brain or spinal meninges.

Documentation Requirements

  • ✓This code should only be used when documentation does not differentiate between cerebral and spinal meningeal involvement.
  • ✓A provider query is strongly recommended to determine the specific location from imaging, operative notes, or pathology reports.
  • ✓Pathology should confirm uncertain behavior classification.

Commonly Confused Codes

  • •D42.0 (cerebral meninges) and D42.1 (spinal meninges) are the site-specific alternatives and should be used whenever the location is documented.
  • •D32.9 (benign meningioma, unspecified) is used for confirmed benign tumors.
  • •C70.9 (malignant neoplasm of meninges, unspecified) is the malignant counterpart.

Child Codes

D42.0Neoplasm of uncertain behavior of cerebral meninges
HCC 23
D42.1Neoplasm of uncertain behavior of spinal meninges
HCC 23
D42.9Neoplasm of uncertain behavior of meninges, unspecified
HCC 23

Code Hierarchy

└D42Neoplasm of uncertain behavior of meninges└D42.9Neoplasm of uncertain behavior of meninges, unspecified
└D42.9Neoplasm of uncertain behavior of meninges, unspecified

Also searched as

  • D42 9
  • D429

For D42.9, 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.

D42.9 maps to CMS-HCC V28 category 23, Prostate, Breast, and Other Cancers and Tumors. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for D42.9. 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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