C45.9
BillableMesothelioma, unspecified
HCC Category Mapping
V28HCC 19 — Lymphoma and Other Cancers
0.105V24HCC 9 — Lung and Other Severe Cancers
0.973ESRDHCC 9 — Lung and Other Severe Cancers
0.000RxHCCHCC 22 — Cancer, Other Specified Sites
0.000What This Code Means
A mesothelioma cancer diagnosis when the specific membrane location (pleura, peritoneum, or pericardium) has not been determined or documented.
Coding Tips
- •Use this code only when the site of mesothelioma is truly unknown; query the provider if site information is available elsewhere in the record
- •This is an unspecified code and should be avoided if any site-specific information can be determined from imaging or pathology reports
Clinical Significance
Mesothelioma is a highly aggressive malignancy primarily caused by asbestos exposure, with a poor prognosis and median survival of 12-21 months. Accurate capture is critical for risk adjustment as it reflects extreme resource utilization including chemotherapy, surgery, and palliative care. The unspecified designation should prompt a query, as site-specific codes (pleural C45.0, peritoneal C45.1, pericardial C45.2) carry different treatment implications.
Documentation Requirements
- ✓Pathology/biopsy confirmation of mesothelioma (epithelioid, sarcomatoid, or biphasic subtype)
- ✓Primary anatomical site (pleura, peritoneum, pericardium, tunica vaginalis) — query if not documented
- ✓History of asbestos exposure if applicable
- ✓Current treatment status (active treatment, surveillance, or palliative care)
- ✓Stage of disease and any metastatic involvement
Commonly Confused Codes
C45.0 (Mesothelioma of pleura) — use when documentation confirms pleural origin; most common site (~80% of cases)C45.1 (Mesothelioma of peritoneum) — use when peritoneal involvement is documentedC78.2 (Secondary malignant neoplasm of pleura) — metastasis TO the pleura from another primary, not mesotheliomaD19.0-D19.9 (Benign neoplasm of mesothelial tissue) — benign counterpart, very different prognosis and HCC impact