C45.1 Mesothelioma of peritoneum

Billable ICD-10-CM code, FY2026. Acts as a Complication or Comorbidity (CC) as a secondary diagnosis.

Applicable to

• Mesothelioma of cul-de-sac
• Mesothelioma of mesentery
• Mesothelioma of mesocolon
• Mesothelioma of omentum
• Mesothelioma of peritoneum (parietal) (pelvic)

Excludes1 (never code together)

• other malignant neoplasm of soft tissue of peritoneum (C48.-)

Risk adjustment (HCC)

• CMS-HCC V28: HCC 19 — Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers
• CMS-HCC V22: HCC 9 — Lung and Other Severe Cancers
• RxHCC V08: HCC 22 — Prostate, Breast, Bladder, and Other Cancers and Tumors
• ESRD V24: HCC 9

MS-DRG index

Defines the logic of DRG(s) 374-376 in MDC 06.

Approximate ICD-9-CM (GEMs)

• 158.8 Malignant neoplasm of specified parts of peritoneum (approximate)

Code annotations containing back-references to C45.1

Back-references to C45

• Type 1 Excludes: C38 Malignant neoplasm of heart, mediastinum and pleura ("mesothelioma (C45.-)")
• Type 1 Excludes: C48 Malignant neoplasm of retroperitoneum and peritoneum ("mesothelioma (C45.-)")
• Type 2 Excludes: C49 Malignant neoplasm of other connective and soft tissue ("mesothelioma (C45.-)")

Diagnosis Index entries for C45.1

• Mesothelioma (malignant) › site classification › mesentery
• Mesothelioma (malignant) › site classification › mesocolon
• Mesothelioma (malignant) › site classification › omentum
• Mesothelioma (malignant) › site classification › peritoneum

Nearby codes

• C45 Mesothelioma
• C45.0 Mesothelioma of pleura
• C45.1 Mesothelioma of peritoneum (this code)
• C45.2 Mesothelioma of pericardium
• C45.7 Mesothelioma of other sites
• C45.9 Mesothelioma, unspecified