C48.2
BillableMalignant neoplasm of peritoneum, unspecified
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C48.2 an HCC code?
Yes. C48.2 maps to Lung and Other Severe Cancers under the CMS-HCC V28 risk adjustment model (and Lung and Other Severe Cancers under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for C48.2
For C48.2 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed C48.2 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C48.2 is the ICD-10-CM diagnosis code for malignant neoplasm of peritoneum, unspecified. A malignant (cancerous) tumor that develops in the peritoneum, which is the thin membrane lining the abdominal cavity, when the specific location within the peritoneum is not specified. C48.2 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of mesothelial and soft tissue (c45-c49).
Under the CMS-HCC V28 risk adjustment model, C48.2 maps to Lung and Other Severe Cancers (HCC 20) with a community, non-dual, aged base RAF weight of 0.000. Under the older V24 model, C48.2 mapped to the same category but with a base RAF weight of 0.973 — V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Use this code only when the peritoneal cancer site is unspecified; if a specific location is documented, use a more specific C48 code. Because C48.2 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for C48.2 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code only when the peritoneal cancer site is unspecified; if a specific location is documented, use a more specific C48 code
- •This code is often used for peritoneal mesothelioma or primary peritoneal cancer when exact anatomical location is unclear
Clinical Significance
Malignant neoplasm of peritoneum, unspecified is a non-specific code that should trigger a query for more detailed anatomical information. While it carries the same high HCC weight as other C48 codes, unspecified codes carry elevated audit risk and should be used only when specific peritoneal sites cannot be determined.
Documentation Requirements
- ✓Pathology confirming primary peritoneal malignancy
- ✓Documentation explaining why specific peritoneal site is unknown
- ✓Evidence of provider query attempt for site specification
- ✓Imaging showing peritoneal involvement
- ✓Distinction from secondary/metastatic peritoneal disease