Lung Cancer HCC Coding Guide
Lung Cancer (e.g. C34.10) maps to HCC 20 (Lung and Other Severe Cancers) under the CMS-HCC V28 risk adjustment model, with a community, non-dual, aged RAF weight of 1.136; V28 reached 100% phase-in for payment year 2026. Z85.118, personal history of other malignant neoplasm of bronchus and lung, is non-HCC under V28. It can also map to HCC 17 (Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic) when the documentation supports those manifestations.
Complete HCC coding guide for Lung Cancer (C34.x) including ICD-10 to HCC mapping, V28 RAF weights, staging documentation, and metastatic coding.
Medically reviewed by Jess P., CPC · Reviewed: May 9, 2026 · Updated for CMS-HCC V28 and FY2026 ICD-10-CM
Quick Facts
HCC Categories
HCC 17, Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic
HCC 20, Lung and Other Severe Cancers
RAF Weight Range
1.136 to 4.209
Community, non-dual, aged (V28)
Model
CMS-HCC V28 (PY2026, 100% phase-in)
10 ICD-10 codes map to payment HCCs
What HCC category does Lung Cancer map to under V28?
Lung cancer is the leading cause of cancer death in the United States, with roughly 238,000 new cases each year. Under CMS-HCC V28, a primary lung malignancy (the C34 codes for upper, middle, and lower lobe and bronchus) maps to HCC 20, "Lung and Other Severe Cancers," carrying a community non-dual aged RAF of about 1.136. Accurate capture still requires the specific lobe, laterality, histology, and whether the tumor is primary or metastatic. Status matters too, so distinguish active treatment, surveillance, and palliative care in the note. Personal history of lung cancer (Z85.118) does not risk-adjust at all, so documenting active versus historical disease is what drives the correct HCC.
ICD-10 to HCC Mapping
| ICD-10 Code | Description | Billable | HCC Mapping |
|---|---|---|---|
| C34.10 | Malignant neoplasm of upper lobe, unspecified bronchus or lung | Yes | HCC 20 |
| C34.11 | Malignant neoplasm of upper lobe, right bronchus or lung | Yes | HCC 20 |
| C34.12 | Malignant neoplasm of upper lobe, left bronchus or lung | Yes | HCC 20 |
| C34.30 | Malignant neoplasm of lower lobe, unspecified bronchus or lung | Yes | HCC 20 |
| C34.90 | Malignant neoplasm of unspecified part of unspecified bronchus or lung | Yes | HCC 20 |
| C34.91 | Malignant neoplasm of unspecified part of right bronchus or lung | Yes | HCC 20 |
| C34.92 | Malignant neoplasm of unspecified part of left bronchus or lung | Yes | HCC 20 |
| C34.31 | Malignant neoplasm of lower lobe, right bronchus or lung | Yes | HCC 20 |
| C34.32 | Malignant neoplasm of lower lobe, left bronchus or lung | Yes | HCC 20 |
| C78.00 | Secondary malignant neoplasm of unspecified lung | Yes | HCC 17 |
| Z85.118 | Personal history of other malignant neoplasm of bronchus and lung | Yes | No HCC (not risk-adjusting under V28) |
RAF weights are community, non-dual, aged base coefficients from the CMS-HCC V28 model (PY2026). Verify against the latest CMS rate announcement for payment calculations.
HCC Buddy maps Lung Cancer from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Documentation Tips
Document the specific lobe (upper, middle, lower, main bronchus) and laterality (right, left) of the primary tumor.
Clearly state whether the cancer is an active malignancy under current treatment or in remission/surveillance.
Document the histological type when known: non-small cell (adenocarcinoma, squamous cell) vs. small cell lung cancer.
Record the TNM staging if available, as it supports medical decision-making documentation.
Document current treatment: chemotherapy, immunotherapy, radiation, targeted therapy, or surgical resection history.
Code metastatic sites separately (C78-C79) in addition to the primary lung cancer code when metastatic disease is documented.
When cancer is in remission or the patient has only a personal history, use Z85.118 instead of the active malignancy code.
Common Coding Mistakes
Continuing to code active malignancy (C34.x) when the cancer has been treated and is in remission, personal history codes (Z85.118) should be used.
Failing to code metastatic sites separately when distant metastases are documented (brain, bone, liver, adrenal).
Not specifying the lobe and laterality when the information is available in pathology or imaging reports.
Confusing primary lung cancer (C34.x) with metastatic cancer to the lung (C78.0x), the distinction is clinically and coding-critical.
V24 to V28 Changes
A key V28 point coders miss is that lung cancer is not always one HCC. Primary lung tumors (C34 codes) land in HCC 20, "Lung and Other Severe Cancers" (community non-dual aged RAF about 1.136). When the cancer has spread, secondary neoplasms of the lung, liver, or brain (such as C78.00 to C78.02, C78.7, C79.31) instead map to HCC 17, "Cancer Metastatic to Lung, Liver, Brain, and Other Organs," which carries a much higher RAF of about 4.209. So metastatic disease is coded to the metastatic category, not the primary-site one. V28 recalibrated and renumbered the cancer hierarchy versus the older model, tightening which conditions qualify, so always confirm the current category rather than reusing a prior-year HCC.
Related Conditions
Related references
Sources
RAF weights are community, non-dual, aged base coefficients from the CMS-HCC V28 model (PY2026). Verify against the latest CMS Rate Announcement for payment.
Verified current to CMS-HCC V28, payment year 2026 — last reviewed May 9, 2026.
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