Skip to content
Dx

ICD-10-CM 2027 diagnosis code

C45.1Mesothelioma of peritoneum

✓ Billable / specificCC — complication/comorbidity

C45.1 is a valid, billable ICD-10-CM code for mesothelioma of peritoneum. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About C45.1

C45.1 is the ICD-10-CM diagnosis code for Mesothelioma of peritoneum. It belongs to category C45 (Mesothelioma), block C45-C49 (malignant neoplasms of mesothelial and soft tissue) and chapter 2 (neoplasms). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within C45 (Mesothelioma), C45.1 is specifically for Mesothelioma of peritoneum. Related codes cover of pleura (C45.0), of pericardium (C45.2), of other sites (C45.7) and unspecified (C45.9).

Don't report C45.1 together with the conditions in its Excludes1 note: other malignant neoplasm of soft tissue of peritoneum (C48.-).

As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.

In MS-DRG v44.0, it is part of the grouping logic for DRG 374 (Digestive Malignancy with MCC, relative weight 2.1109), DRG 375 (Digestive Malignancy with CC, relative weight 1.1838) and DRG 376 (Digestive Malignancy without CC/MCC, relative weight 0.8929), in MDC 06 (Diseases and Disorders of the Digestive System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 158.8 (malignant neoplasm of specified parts of peritoneum).

Coding notes

Applicable toConditions and synonyms classified to this code
  • Mesothelioma of cul-de-sac
  • Mesothelioma of mesentery
  • Mesothelioma of mesocolon
  • Mesothelioma of omentum
  • Mesothelioma of peritoneum (parietal) (pelvic)
Excludes1Not coded here — never report together with this code
  • other malignant neoplasm of soft tissue of peritoneum (C48.-)

Notes that apply from higher levels

Instructions written at a parent level also apply to C45.1.

Broader instructions also apply from Chapter 2: Neoplasms.

Alphabetic index entries

4 entries

Terms in the official ICD-10-CM index that lead to C45.1.

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

ICD-9-CM equivalent

Converter →
  • 158.8Malignant neoplasm of specified parts of peritoneumapproximate

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about C45.1

Is C45.1 billable?

Yes. C45.1 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can C45.1 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict C45.1 as a principal diagnosis.

Is C45.1 a CC or MCC?

C45.1 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.

What DRG does C45.1 group to?

C45.1 is used in the MS-DRG v44.0 logic for MS-DRG 374 (Digestive Malignancy with MCC), MS-DRG 375 (Digestive Malignancy with CC) and MS-DRG 376 (Digestive Malignancy without CC/MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for C45.1?

The CMS General Equivalence Mappings map C45.1 to ICD-9-CM 158.8.