C78.30
BillableSecondary malignant neoplasm of unspecified respiratory organ
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is C78.30 an HCC code?
Yes. C78.30 maps to Metastatic Cancer and Acute Leukemia under the CMS-HCC V28 risk adjustment model (and Metastatic Cancer and Acute Leukemia 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 C78.30
For C78.30 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 C78.30 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
C78.30 is the ICD-10-CM diagnosis code for secondary malignant neoplasm of unspecified respiratory organ. Cancer that has spread to an unspecified part of the lungs or respiratory system from another location in the body. C78.30 sits in the ICD-10-CM chapter for neoplasms (c00-d49), within the section covering malignant neoplasms of ill-defined, other secondary and unspecified sites (c76-c80).
Under the CMS-HCC V28 risk adjustment model, C78.30 maps to Metastatic Cancer and Acute Leukemia (HCC 17) with a community, non-dual, aged base RAF weight of 0.368. Under the older V24 model, C78.30 mapped to the same category but with a base RAF weight of 2.484 — 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 specific respiratory organ cannot be identified; if known, use a more specific C78.3x code. Because C78.30 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 C78.30 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 specific respiratory organ cannot be identified; if known, use a more specific C78.3x code
- •Always code the primary cancer site separately and ensure documentation specifies this is metastatic disease
Clinical Significance
Secondary malignant neoplasm of an unspecified respiratory organ indicates metastatic cancer has spread to the respiratory system but the specific organ cannot be identified. This non-specific code should be used only as a last resort when documentation does not clarify whether the lung, pleura, mediastinum, or other respiratory structure is involved.
Documentation Requirements
- ✓Primary cancer site documented and coded separately
- ✓Best available description of the respiratory system involvement
- ✓Imaging reports should be reviewed for specific anatomical localization
- ✓Provider query initiated when documentation is insufficient for a more specific code
- ✓Clinical context — symptoms, imaging findings, treatment approach