Skip to content
HCC Buddy home

C78.02 ICD-10-CM Code: Secondary malignant neoplasm of left lung

C78.02 maps to CMS-HCC V28 17. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupC78.02

FY 2026 Apr update / Neoplasms (C00-D49) / Malignant neoplasms of ill-defined, other secondary and unspecified sites (C76-C80)

C78.02

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Secondary malignant neoplasm of left lung

Cancer that has spread to the tissue of the left lung from a cancer that originated elsewhere in the body.

Buddy the Bee presenting code insight

Buddy Insight

Secondary malignant neoplasm of the left lung confirms metastatic cancer with documented laterality.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 17

Code-level coefficient reference

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 008

Code-level coefficient reference

ESRD/PACE

HCC 8

Code-level coefficient reference

RXHCC

HCC 18

Code-level coefficient reference

Code Book Path

Official
C78Secondary malignant neoplasm of respiratory and digestive organsC78.0Secondary malignant neoplasm of lungC78.02Secondary malignant neoplasm of left lung

Inclusion Terms

Official

No inclusion terms are included in this display for C78.02. Check the code and parent instructions in the Code Book.

Excludes 2

Official
  • lymph node metastases (C77.0)Inherited from C78

Related Codes

Official
C78.00Secondary malignant neoplasm of unspecified lungC78.01Secondary malignant neoplasm of right lung

Includes

Official

No Includes notes are included in this display for C78.02. Check the code and parent instructions in the Code Book.

Excludes 1

Official
  • secondary carcinoid tumors of liver (C7B.02)Inherited from C78
  • secondary carcinoid tumors of peritoneum (C7B.04)Inherited from C78

Code First

Official

No Code First sequencing instructions are included in this display for C78.02. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for C78.02. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for C78.02. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Primary cancer site must be documented and coded separately
Explicit documentation of left lung involvement — 'left lung metastasis' or equivalent
Imaging or pathological confirmation of metastatic disease
Number and distribution of metastatic lesions

MEAT Support

HCC Buddy guidance
Primary cancer site must be documented and coded separately
Explicit documentation of left lung involvement — 'left lung metastasis' or equivalent
Imaging or pathological confirmation of metastatic disease
Number and distribution of metastatic lesions

Audit Caution

HCC Buddy guidance
Using unspecified lung code when left lung is clearly documented in imaging or operative reports
Coding left lung metastasis when the left lung is actually the primary cancer site
Not querying when documentation says 'lung metastasis' without specifying which lung
Failing to code both C78.01 and C78.02 when bilateral lung metastases are documented

Common Mistakes

HCC Buddy guidance
C34.12 — Primary malignant neoplasm of upper lobe, left bronchus or lung; primary versus secondary distinction is critical
C78.00 — Secondary malignant neoplasm of unspecified lung; always specify laterality when documented
C78.01 — Secondary malignant neoplasm of right lung; verify laterality from imaging reports
C78.2 — Secondary malignant neoplasm of pleura; left pleural disease requires a different code

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is C78.02 an HCC code?

Yes. C78.02 (Secondary malignant neoplasm of left lung) maps to HCC 17, Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 4.209. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: C78.02 is billable and maps to V28 HCC 17, Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
C78.02
Description
Secondary malignant neoplasm of left lung
HCC (V28)
HCC 17 — Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic
RAF reference coefficient
4.209
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 17, Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic
4.209
ESRDHCC 8, Metastatic Cancer and Acute Leukemia
Not separately weighted
RxHCCHCC 18, Secondary Cancer of Lung, Liver, Brain, and Other Sites
Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work C78.02 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for C78.02

For C78.02, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

  • 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

Coder workflow notes

Get the V28 mapping + MEAT cheat sheet

One printable reference: check representative V28 mappings and the documentation reminders your note needs. Free, no card.

Free PDF. No card. Unsubscribe anytime.

What This Code Means

C78.02 is the ICD-10-CM diagnosis code for secondary malignant neoplasm of left lung. Cancer that has spread to the tissue of the left lung from a cancer that originated elsewhere in the body. C78.02 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, C78.02 maps to Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic (HCC 17) with a source-labeled community, non-dual, aged reference coefficient of 4.209. No V24 mapping is shown for C78.02; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

This code is specific to left lung involvement; verify laterality in documentation before assigning this code. For C78.02, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, and MEAT documentation criteria for C78.02 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •This code is specific to left lung involvement; verify laterality in documentation before assigning this code
  • •Always identify and code the primary cancer site separately when known

Clinical Significance

Secondary malignant neoplasm of the left lung confirms metastatic cancer with documented laterality. Left lung metastases carry the same clinical significance as right-sided involvement but require laterality documentation for accurate coding. Proper laterality capture demonstrates quality documentation and supports precise treatment planning.

Documentation Requirements

  • ✓Primary cancer site must be documented and coded separately
  • ✓Explicit documentation of left lung involvement — 'left lung metastasis' or equivalent
  • ✓Imaging or pathological confirmation of metastatic disease
  • ✓Number and distribution of metastatic lesions
  • ✓Treatment plan or status — surgical candidacy, systemic therapy, or palliation

Commonly Confused Codes

  • •C34.12: Primary malignant neoplasm of upper lobe, left bronchus or lung; primary versus secondary distinction is critical
  • •C78.00: Secondary malignant neoplasm of unspecified lung; always specify laterality when documented
  • •C78.01: Secondary malignant neoplasm of right lung; verify laterality from imaging reports
  • •C78.2: Secondary malignant neoplasm of pleura; left pleural disease requires a different code

Child Codes

C78.00Secondary malignant neoplasm of unspecified lung
HCC 17
C78.01Secondary malignant neoplasm of right lung
HCC 17
C78.02Secondary malignant neoplasm of left lung
HCC 17

Code Hierarchy

└C78Secondary malignant neoplasm of respiratory and digestive organs└C78.0Secondary malignant neoplasm of lung└C78.02Secondary malignant neoplasm of left lung
└C78.02Secondary malignant neoplasm of left lung

For C78.02, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

C78.02 maps to CMS-HCC V28 category 17, Cancer Metastatic to Lung, Liver, Brain, and Other Organs; Acute Myeloid Leukemia Except Promyelocytic. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for C78.02. Review its source-labeled HCC coefficient above, check the RAF Calculator with complete member context for CMS-HCC V28 PY2026, and confirm the documentation the chart needs before the code is submitted. HCC Buddy shows no RAF score unless every required source and calculation check passes.

More on C78.02

Related condition guides

Work C78.02 in HCC Buddy

Open C78.02 in the Code Book for the full Index-to-Tabular path, MEAT checklist, and V28 HCC mapping, or in the Encoder to code from a keyword search. Pro includes 7 days to try everything, no card required.

Open in Code BookOpen in EncoderStart Pro