ICD-10-CM 2027
ICD-10 code for Mesothelioma
From the official ICD-10-CM alphabetic index entry “Mesothelioma (malignant)”. Page updated September 29, 2026.
About coding Mesothelioma
The ICD-10-CM code for Mesothelioma is C45.9 (Mesothelioma, unspecified). The official index lists 45 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on C45.9.
Within C45, choose C45.9 (unspecified) only when documentation doesn't support a more specific option: of pleura (C45.0), of peritoneum (C45.1), of pericardium (C45.2) and of other sites (C45.7).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 826 (Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Major O.R. Procedures with MCC, relative weight 4.7581), DRG 827 (Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Major O.R. Procedures with CC, relative weight 2.3896), DRG 828 (Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Major O.R. Procedures without CC/MCC, relative weight 1.6955), DRG 829 (Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Other Procedures with CC/MCC, relative weight 3.1281), DRG 830 (Myeloproliferative Disorders or Poorly Differentiated Neoplasms with Other Procedures without CC/MCC, relative weight 1.4859), DRG 843 (Other Myeloproliferative Disorders or Poorly Differentiated Neoplastic Diagnoses with MCC, relative weight 1.9453) and 2 more, in MDC 17 (Myeloproliferative Diseases and Disorders, Poorly Differentiated Neoplasms), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
More specific Mesothelioma codes (official index)
- benign
- mesentery D19.1 — Benign neoplasm of mesothelial tissue of peritoneum
- mesocolon D19.1 — Benign neoplasm of mesothelial tissue of peritoneum
- omentum D19.1 — Benign neoplasm of mesothelial tissue of peritoneum
- peritoneum D19.1 — Benign neoplasm of mesothelial tissue of peritoneum
- pleura D19.0 — Benign neoplasm of mesothelial tissue of pleura
- specified site NEC D19.7 — Benign neoplasm of mesothelial tissue of other sites
- unspecified site D19.9 — Benign neoplasm of mesothelial tissue, unspecified
- biphasic C45.9 — Mesothelioma, unspecified
- benign
- mesentery D19.1 — Benign neoplasm of mesothelial tissue of peritoneum
- mesocolon D19.1 — Benign neoplasm of mesothelial tissue of peritoneum
- omentum D19.1 — Benign neoplasm of mesothelial tissue of peritoneum
- peritoneum D19.1 — Benign neoplasm of mesothelial tissue of peritoneum
- pleura D19.0 — Benign neoplasm of mesothelial tissue of pleura
- specified site NEC D19.7 — Benign neoplasm of mesothelial tissue of other sites
- unspecified site D19.9 — Benign neoplasm of mesothelial tissue, unspecified
- cystic D48.4 — Neoplasm of uncertain behavior of peritoneum
- epithelioid C45.9 — Mesothelioma, unspecified
- benign
- mesentery D19.1 — Benign neoplasm of mesothelial tissue of peritoneum
- mesocolon D19.1 — Benign neoplasm of mesothelial tissue of peritoneum
- omentum D19.1 — Benign neoplasm of mesothelial tissue of peritoneum
- peritoneum D19.1 — Benign neoplasm of mesothelial tissue of peritoneum
- pleura D19.0 — Benign neoplasm of mesothelial tissue of pleura
- specified site NEC D19.7 — Benign neoplasm of mesothelial tissue of other sites
- unspecified site D19.9 — Benign neoplasm of mesothelial tissue, unspecified
- fibrous C45.9 — Mesothelioma, unspecified
- benign
- mesentery D19.1 — Benign neoplasm of mesothelial tissue of peritoneum
- mesocolon D19.1 — Benign neoplasm of mesothelial tissue of peritoneum
- omentum D19.1 — Benign neoplasm of mesothelial tissue of peritoneum
- peritoneum D19.1 — Benign neoplasm of mesothelial tissue of peritoneum
- pleura D19.0 — Benign neoplasm of mesothelial tissue of pleura
- specified site NEC D19.7 — Benign neoplasm of mesothelial tissue of other sites
- unspecified site D19.9 — Benign neoplasm of mesothelial tissue, unspecified
- site classification
- liver C45.7 — Mesothelioma of other sites
- lung C45.7 — Mesothelioma of other sites
- mediastinum C45.7 — Mesothelioma of other sites
- mesentery C45.1 — Mesothelioma of peritoneum
- mesocolon C45.1 — Mesothelioma of peritoneum
- omentum C45.1 — Mesothelioma of peritoneum
- pericardium C45.2 — Mesothelioma of pericardium
- peritoneum C45.1 — Mesothelioma of peritoneum
- pleura C45.0 — Mesothelioma of pleura
- parietal C45.0 — Mesothelioma of pleura
- retroperitoneum C45.7 — Mesothelioma of other sites
- specified site NEC C45.7 — Mesothelioma of other sites
- unspecified C45.9 — Mesothelioma, unspecified
Common questions about Mesothelioma ICD-10 codes
What is the ICD-10 code for Mesothelioma?
- C45.9 — Mesothelioma, unspecified. More specific codes apply when the documentation supports them: D19.1, D19.1, D19.1, D19.1 and others below.
What is the ICD-10 code for biphasic mesothelioma?
- C45.9 — Mesothelioma, unspecified.
What is the ICD-10 code for cystic mesothelioma?
- D48.4 — Neoplasm of uncertain behavior of peritoneum.
What is the ICD-10 code for epithelioid mesothelioma?
- C45.9 — Mesothelioma, unspecified.
What is the ICD-10 code for fibrous mesothelioma?
- C45.9 — Mesothelioma, unspecified.
Is C45.9 billable?
- Yes. C45.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can C45.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict C45.9 as a principal diagnosis.
Is C45.9 a CC or MCC?
- No. C45.9 is neither a CC nor an MCC under MS-DRG v44.0.