C71.8 maps to CMS-HCC V28 20. 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

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupC71.8

Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of eye, brain and other parts of central nervous system (C69-C72)

C71.8

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

Malignant neoplasm of overlapping sites of brain

Cancer of the brain that involves multiple overlapping areas or sites within the brain. This code is used when the tumor crosses boundaries between different brain regions.

Buddy Insight

Overlapping sites of brain cancer indicates a tumor that crosses boundaries between two or more distinct brain regions, typically reflecting a large or diffusely infiltrating tumor such as butterfly glioblastoma (crossing the corpus callosum) or multifocal brain cancer.

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

Mapped

HCC 20

Lung and Other Severe Cancers

Coefficient HCC 20: 1.136 (Community Non-Dual Aged (CNA))

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

Mapped

HCC 009

HHS-HCC 009 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 10

Lymphoma and Other Cancers

Code-level coefficient reference

RXHCC

Mapped

HCC 22

Prostate, Breast, Bladder, an...

Code-level coefficient reference

Code Book Path

Official

C71Malignant neoplasm of brain C71.8Malignant neoplasm of overlapping sites of brain

Inclusion Terms

Official

No inclusion terms are included in this display for C71.8. Check the code and parent instructions in the Code Book.

Excludes 2

Official

No Excludes 2 notes are included in this display for C71.8. Check the code and parent instructions in the Code Book.

Related Codes

Official

C71.0Malignant neoplasm of cerebrum, except lobes and ventricles C71.1Malignant neoplasm of frontal lobe C71.2Malignant neoplasm of temporal lobe C71.3Malignant neoplasm of parietal lobe C71.4Malignant neoplasm of occipital lobe

Includes

Official

No Includes notes are included in this display for C71.8. Check the code and parent instructions in the Code Book.

Excludes 1

Official

malignant neoplasm of cranial nerves (C72.2-C72.5)Inherited from C71
retrobulbar malignant neoplasm (C69.6-)Inherited from C71

Code First

Official

No Code First sequencing instructions are included in this display for C71.8. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for C71.8. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for C71.8. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

Pathology confirming malignancy with histological type and grade

MRI documenting involvement of two or more distinct brain regions

Documentation of which specific brain regions are involved

Assessment of functional deficits reflecting multi-regional involvement

MEAT Support

HCC Buddy guidance

Pathology confirming malignancy with histological type and grade

MRI documenting involvement of two or more distinct brain regions

Documentation of which specific brain regions are involved

Assessment of functional deficits reflecting multi-regional involvement

Audit Caution

HCC Buddy guidance

Confusing 'overlapping sites' with 'unspecified' — overlapping requires identification of multiple involved regions

Using this code for multiple separate brain metastases from systemic cancer

Not documenting the specific overlapping regions, which reduces clinical utility

Using overlapping code when the tumor is primarily in one region with minimal extension

Common Mistakes

HCC Buddy guidance

C71.0-C71.7 — Specific brain region codes: use overlapping code only when tumor clearly involves multiple regions; if one primary region predominates, code that region

C71.9 — Brain, unspecified: overlapping means multiple known sites; unspecified means the site is unknown

C79.31 — Brain metastasis: multifocal brain metastases from systemic cancer should not be coded as primary overlapping brain cancer

C71.0 — Cerebrum except lobes: consider this code for deep central tumors that do not specifically cross lobar boundaries

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 C71.8 an HCC code?

Yes. C71.8 (Malignant neoplasm of overlapping sites of brain) maps to HCC 20, Lung and Other Severe Cancers under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 1.136. 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: C71.8 is billable and maps to V28 HCC 20, Lung and Other Severe Cancers. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: C71.8
Description: Malignant neoplasm of overlapping sites of brain
HCC (V28): HCC 20 — Lung and Other Severe Cancers
RAF reference coefficient: 1.136
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 20, Lung and Other Severe Cancers

1.136

ESRDHCC 10, Lymphoma and Other Cancers

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 C71.8 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C71.8

For C71.8, 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

C71.8 is the ICD-10-CM diagnosis code for malignant neoplasm of overlapping sites of brain. Cancer of the brain that involves multiple overlapping areas or sites within the brain. This code is used when the tumor crosses boundaries between different brain regions. C71.8 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of eye, brain and other parts of central nervous system (c69-c72).

Under the CMS-HCC V28 risk adjustment model, C71.8 maps to Lung and Other Severe Cancers (HCC 20) with a source-labeled community, non-dual, aged reference coefficient of 1.136. 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 the tumor clearly involves more than one distinct brain region. For C71.8, 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 C71.8 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 the tumor clearly involves more than one distinct brain region
•Document all involved sites in the medical record for clarity and treatment planning

Clinical Significance

Documentation Requirements

✓Pathology confirming malignancy with histological type and grade
✓MRI documenting involvement of two or more distinct brain regions
✓Documentation of which specific brain regions are involved
✓Assessment of functional deficits reflecting multi-regional involvement
✓Treatment plan addressing the diffuse nature of the disease

Commonly Confused Codes

•C71.0-C71.7: Specific brain region codes: use overlapping code only when tumor clearly involves multiple regions; if one primary region predominates, code that region
•C71.9: Brain, unspecified: overlapping means multiple known sites; unspecified means the site is unknown
•C79.31: Brain metastasis: multifocal brain metastases from systemic cancer should not be coded as primary overlapping brain cancer
•C71.0: Cerebrum except lobes: consider this code for deep central tumors that do not specifically cross lobar boundaries