2026 ICD-10-CM Diagnosis Code C70.9Malignant neoplasm of meninges, unspecified

ICD-10-CM CodesC00–D49C69-C72C70

ICD-10-CM C70.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

C70.9 is a billable ICD-10-CM diagnosis code for malignant neoplasm of meninges, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). Coders also document this condition as diffuse melanosis of meninges. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Nervous system cancers - brain.

Code Identity

ICD-10-CM Code
C70.9
Billable Status
Yes — Valid for Submission
Code Describes
Malignant neoplasm of meninges, unspecified
Short Description
Malignant neoplasm of meninges, unspecified
Same as the full description in the CMS dataset.
Parent Code
Malignant neoplasm of meninges

Code Classification

ChapterC00–D49Neoplasms
SectionC69-C72Malignant neoplasms of eye, brain and other parts of central nervous system
CategoryC70Malignant neoplasm of meninges
This CodeC70.9Malignant neoplasm of meninges, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Diffuse melanosis of meninges
  • Malignant melanoma of meninges
  • Malignant neoplasm of meninges
  • Metastatic malignant neoplasm of meninges
  • Primary malignant meningioma
  • Primary malignant neoplasm of meninges
  • Primary melanocytic lesion of meninges

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR NEO048
Nervous system cancers - brain
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Arachnoid

    a delicate membrane enveloping the brain and spinal cord. it lies between the pia mater and the dura mater. it is separated from the pia mater by the subarachnoid cavity which is filled with cerebrospinal fluid.
  • Arachnoid Cysts

    intracranial or spinal cavities containing a cerebrospinal-like fluid, the wall of which is composed of arachnoidal cells. they are most often developmental or related to trauma. intracranial arachnoid cysts usually occur adjacent to arachnoidal cistern and may present with hydrocephalus; headache; seizures; and focal neurologic signs. (from joynt, clinical neurology, 1994, ch44, pp105-115)
  • Arachnoiditis

    acute or chronic inflammation of the arachnoid membrane of the meninges most often involving the spinal cord or base of the brain. this term generally refers to a persistent inflammatory process characterized by thickening of the arachnoid membrane and dural adhesions. associated conditions include prior surgery, infections, trauma, subarachnoid hemorrhage, and chemical irritation. clinical features vary with the site of inflammation, but include cranial neuropathies, radiculopathies, and myelopathies. (from joynt, clinical neurology, 1997, ch48, p25)
  • Medulloblastoma

    a malignant neoplasm that may be classified either as a glioma or as a primitive neuroectodermal tumor of childhood (see neuroectodermal tumor, primitive). the tumor occurs most frequently in the first decade of life with the most typical location being the cerebellar vermis. histologic features include a high degree of cellularity, frequent mitotic figures, and a tendency for the cells to organize into sheets or form rosettes. medulloblastoma have a high propensity to spread throughout the craniospinal intradural axis. (from devita et al., cancer: principles and practice of oncology, 5th ed, pp2060-1)
  • Meninges

    the three membranes that cover the brain and the spinal cord. they are the dura mater, the arachnoid, and the pia mater.
  • Meningocele

    a congenital or acquired protrusion of the meninges, unaccompanied by neural tissue, through a bony defect in the skull or vertebral column.
  • Pia Mater

    the innermost layer of the three meninges covering the brain and spinal cord. it is the fine vascular membrane that lies under the arachnoid and the dura mater.

Table of NeoplasmsClinical

Anatomical sites in the Table of Neoplasms that reference this code family.

SiteMalig.
Primary
Malig.
Secondary
Ca
in situ
BenignUncertainUnspec.
arachnoidC70.9C79.49D32.9D42.9D49.7
dura (cranial) (mater)C70.9C79.49D32.9D42.9D49.7
meningesC70.9C79.49D32.9D42.9D49.7
pia materC70.9C79.40D32.9D42.9D49.7
subduralC70.9C79.32D32.9D42.9D49.7

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Convert C70.9 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
192.1 Mal neo cerebral mening
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About C70.9Overview

Is C70.9 (Malignant neoplasm of meninges) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report malignant neoplasm of meninges, unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What is the ICD-9 equivalent of C70.9?

Under the General Equivalence Mappings, malignant neoplasm of meninges, unspecified converts to ICD-9-CM 192.1 (mal neo cerebral mening). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.