2027 ICD-10-CM Diagnosis Code D33.1Benign neoplasm of brain, infratentorial
ICD-10-CM Codes›C00–D49›D10-D36›D33
- Billable — Valid for Submission
- Risk Adjusts — HCC 23
- Chronic Condition
D33.1 is a billable ICD-10-CM diagnosis code for benign neoplasm of brain, infratentorial. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 54 through 55. Coders also document this condition as benign cerebellopontine angle meningioma. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Benign neoplasms.
For Medicare Advantage risk adjustment, D33.1 maps to CMS-HCC Category 23 (Prostate, Breast, and Other Cancers and Tumors) under the V28 model, adding a risk factor of about 0.186 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
D33.1 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Benign cerebellopontine angle meningioma
- Benign neoplasm of brain stem
- Benign neoplasm of cerebellum
- Benign neoplasm of infratentorial brain
- Benign neoplasm of medulla oblongata
- Benign neoplasm of pons
- Benign neoplasm of spinal extradural space
- Cerebellopontine angle neoplasm
- Neoplasm of extradural space
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to D33.1: its own notes plus those printed at D33 and Chapter 2. A note printed at a category, block or chapter applies to every code under it.
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- Benign neoplasm of brain stem
- Benign neoplasm of cerebellum
- Benign neoplasm of fourth ventricle
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
Notes
General instructions on how these codes are used.
- Functional activity
- All neoplasms are classified in this chapter, whether they are functionally active or not. An additional code from Chapter 4 may be used, to identify functional activity associated with any neoplasm.
- Morphology [Histology]
- Chapter 2 classifies neoplasms primarily by site (topography), with broad groupings for behavior, malignant, in situ, benign, etc. The Table of Neoplasms should be used to identify the correct topography code. In a few cases, such as for malignant melanoma and certain neuroendocrine tumors, the morphology (histologic type) is included in the category and codes.
- Primary malignant neoplasms overlapping site boundaries
- A primary malignant neoplasm that overlaps two or more contiguous (next to each other) sites should be classified to the subcategory/code .8 ('overlapping lesion'), unless the combination is specifically indexed elsewhere. For multiple neoplasms of the same site that are not contiguous, such as tumors in different quadrants of the same breast, codes for each site should be assigned.
- Malignant neoplasm of ectopic tissue
- Malignant neoplasms of ectopic tissue are to be coded to the site mentioned, e.g., ectopic pancreatic malignant neoplasms are coded to pancreas, unspecified (C25.9).
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name D33.1, its category, or a range that includes it.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Papilloma See Also: Neoplasm, benign, by site;
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Benign Infratentorial Neoplasm
a neoplasm that arises from the infratentorial region and is characterized by the absence of atypical or malignant cytological and architectural features, and absence of invasive features or metastatic potential.
Table of NeoplasmsClinical
Anatomical sites in the Table of Neoplasms that reference this code family.
| Site | Malig. Primary | Malig. Secondary | Ca in situ | Benign | Uncertain | Unspec. |
|---|---|---|---|---|---|---|
| basis pedunculi | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| brain NEC › cerebellopontine angle | C71.6 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| brain NEC › cerebellum NOS | C71.6 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| brain NEC › choroid plexus | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| brain NEC › medulla oblongata | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| brain NEC › midbrain | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| brain NEC › peduncle | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| brain NEC › pons | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| brain NEC › stem | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| brain NEC › ventricle (floor) › fourth | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| cerebellopontine (angle) | C71.6 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| cerebellum, cerebellar | C71.6 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| cerebrum, cerebral (cortex) (hemisphere) (white matter) › peduncle | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| cerebrum, cerebral (cortex) (hemisphere) (white matter) › ventricle › fourth | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| ependyma (brain) › fourth ventricle | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| medulla › oblongata | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| midbrain | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| olive (brain) | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| peduncle, cerebral | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| pons (varolii) | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| pyramid (brain) | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| spine, spinal (column) › bulb | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| stem, brain | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| ventricle (cerebral) (floor) (lateral) (third) › fourth | C71.7 | C79.31 | – | D33.1 | D43.1 | D49.6 |
| vermis, cerebellum | C71.6 | C79.31 | – | D33.1 | D43.1 | D49.6 |
Patient EducationClinical
Benign Tumors
Tumors are abnormal growths in your body. They can be either benign or malignant. Benign tumors aren't cancer. Malignant ones are. Benign tumors grow only in one place. They cannot spread or invade other parts of your body. Even so, they can be dangerous if they press on vital organs, such as your brain.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert D33.1 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About D33.1Overview
What is the ICD-10 code for benign neoplasm of brain, infratentorial?
The ICD-10-CM code for benign neoplasm of brain, infratentorial is D33.1 (sometimes written as D331). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is D33.1 a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report benign neoplasm of brain, infratentorial on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does D33.1 group to?
When benign neoplasm of brain, infratentorial is the principal diagnosis on an inpatient stay, it groups to MS-DRG 55, 54, with relative weights from 1.0291 to 1.5197 depending on complications. Higher weights mean higher Medicare reimbursement.
Can D33.1 be reported with a code from D18.0?
Not as a rule. The Excludes1 note at D33, which applies to D33.1, lists "angioma (D18.0-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
What is the ICD-9 equivalent of D33.1?
Under the General Equivalence Mappings, benign neoplasm of brain, infratentorial converts to ICD-9-CM 225.0 (benign neoplasm brain). The mapping is approximate, so confirm the match fits the documentation.
What HCC is D33.1?
D33.1 (benign neoplasm of brain, infratentorial) maps to CMS-HCC Category 23 (Prostate, Breast, and Other Cancers and Tumors), commonly written as HCC 23, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 12 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 22.
Does D33.1 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, D33.1 adds a risk adjustment factor of about 0.186 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.186 to 0.237 depending on the payment segment). A more severe related category (HCC 17, HCC 18, HCC 19, HCC 20, HCC 21, and HCC 22) supersedes it when both are reported. See the full factor table on the HCC 23 category page.
