2027 ICD-10-CM Diagnosis Code C34.12Malignant neoplasm of upper lobe, left bronchus or lung
ICD-10-CM Codes›C00–D49›C30-C39›C34
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 20
- Chronic Condition
C34.12 is a billable ICD-10-CM diagnosis code for malignant neoplasm of upper lobe, left bronchus or lung. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 180 through 182. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 29 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Respiratory cancers.
For Medicare Advantage risk adjustment, C34.12 maps to CMS-HCC Category 20 (Lung and Other Severe Cancers) under the V28 model, adding a risk factor of about 1.136 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Quality Payment Program MeasuresBilling
Medicare quality measures that can apply when C34.12 is part of the patient record.
Lung Cancer Reporting (Biopsy/Cytology Specimens)
High Priority: YES
Measure Type: Process
Submission Methods: Claims, Registry
Description: Pathology reports based on lung biopsy and/or cytology specimens with a diagnosis of primary non-small cell lung cancer classified into specific histologic type following the International Association for the Study of Lung Cancer (IASLC) guidance or classified as non-small cell lung cancer not otherwise specified (NSCLC-NOS) with an explanation included in the pathology report.
Lung Cancer Reporting (Resection Specimens)
High Priority: YES
Measure Type: Process
Submission Methods: Claims, Registry
Description: Pathology reports based on lung resection specimens with a diagnosis of primary lung carcinoma that include the pT category, pN category and for non-small cell lung cancer (NSCLC), histologic type.
Medicare Risk Adjustment (HCC)Billing
C34.12 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Adenocarcinoma of left lung
- Malignant neoplasm of upper lobe bronchus
- Malignant neoplasm of upper lobe of left lung
- Neoplasm of bronchus of left upper lobe
- Primary adenocarcinoma of upper lobe of left lung
- Primary large cell carcinoma of lung
- Primary large cell carcinoma of upper lobe of left lung
- Primary malignant neoplasm of bronchus of left upper lobe
- Primary malignant neoplasm of upper lobe of left lung
- Primary non-small cell carcinoma of left lung
- Primary non-small cell carcinoma of upper lobe of left lung
- Primary small cell carcinoma of left lung
- Primary small cell carcinoma of upper lobe of left lung
- Primary squamous cell carcinoma of bronchus
- Primary squamous cell carcinoma of bronchus in left upper lobe
- Primary squamous cell carcinoma of left lung
- Primary squamous cell carcinoma of upper lobe of left lung
- Squamous cell carcinoma of bronchus in left upper lobe
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to C34.12: its own notes plus those printed at C34, block C30-C39, and Chapter 2. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- malignant neoplasm of middle ear
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
- mesothelioma (C45.-)
Notes
General instructions on how these codes are used.
- Functional activity
- All neoplasms are classified in this chapter, whether they are functionally active or not. An additional code from Chapter 4 may be used, to identify functional activity associated with any neoplasm.
- Morphology [Histology]
- Chapter 2 classifies neoplasms primarily by site (topography), with broad groupings for behavior, malignant, in situ, benign, etc. The Table of Neoplasms should be used to identify the correct topography code. In a few cases, such as for malignant melanoma and certain neuroendocrine tumors, the morphology (histologic type) is included in the category and codes.
- Primary malignant neoplasms overlapping site boundaries
- A primary malignant neoplasm that overlaps two or more contiguous (next to each other) sites should be classified to the subcategory/code .8 ('overlapping lesion'), unless the combination is specifically indexed elsewhere. For multiple neoplasms of the same site that are not contiguous, such as tumors in different quadrants of the same breast, codes for each site should be assigned.
- Malignant neoplasm of ectopic tissue
- Malignant neoplasms of ectopic tissue are to be coded to the site mentioned, e.g., ectopic pancreatic malignant neoplasms are coded to pancreas, unspecified (C25.9).
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name C34.12, its category, or a range that includes it.
Applicable To 2
These notes mention C34.12.
Excludes2 1
These codes carry an Excludes2 note naming C34.12: its condition is not part of those codes, and both may be reported when the patient has both.
- Block J60-J70 Lung diseases due to external agentsmalignant neoplasm of bronchus and lung (C34.-) names C34.-, which includes this code
Code First 1
These codes say to code first a condition named in the note, and C34.12 is one of the conditions named.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Table of NeoplasmsClinical
Anatomical sites in the Table of Neoplasms that reference this code family.
| Site | Malig. Primary | Malig. Secondary | Ca in situ | Benign | Uncertain | Unspec. |
|---|---|---|---|---|---|---|
| bronchus › upper lobe of lung | C34.1 | C78.0 | D02.2 | D14.3 | D38.1 | D49.1 |
| lingula, lung | C34.1 | C78.0 | D02.2 | D14.3 | D38.1 | D49.1 |
| lung › azygos lobe | C34.1 | C78.0 | D02.2 | D14.3 | D38.1 | D49.1 |
| lung › lingula | C34.1 | C78.0 | D02.2 | D14.3 | D38.1 | D49.1 |
| lung › upper lobe | C34.1 | C78.0 | D02.2 | D14.3 | D38.1 | D49.1 |
Patient EducationClinical
Lung Cancer
Lung cancer is cancer that forms in tissues of the lung, usually in the cells that line the air passages. It is the leading cause of cancer death in both men and women.
The full article covers:
- What is lung cancer?
- Who is more likely to develop lung cancer?
- What are the symptoms of lung cancer?
- How is lung cancer diagnosed?
- What are the treatments for lung cancer?
- Can lung cancer be prevented?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert C34.12 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About C34.12Overview
What is the ICD-10 code for malignant neoplasm of upper lobe, left bronchus or lung?
The ICD-10-CM code for malignant neoplasm of upper lobe, left bronchus or lung is C34.12 (sometimes written as C3412). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is C34.12 (Malignant neoplasm of upper lobe, bronchus or lung) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report malignant neoplasm of upper lobe, left bronchus or lung on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does C34.12 group to?
When malignant neoplasm of upper lobe, left bronchus or lung is the principal diagnosis on an inpatient stay, it groups to MS-DRG 181, 180, 182, with relative weights from 0.7436 to 1.7800 depending on complications. Higher weights mean higher Medicare reimbursement.
Is C34.12 a CC or MCC?
CMS lists C34.12 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 29 closely related codes in its exclusion list.
Can C34.12 be reported with a code from C46.5?
Not as a rule. The Excludes1 note at C34, which applies to C34.12, lists "Kaposi's sarcoma of lung (C46.5-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
What HCC is C34.12?
C34.12 (malignant neoplasm of upper lobe, left bronchus or lung) maps to CMS-HCC Category 20 (Lung and Other Severe Cancers), commonly written as HCC 20, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 9 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 20.
Does C34.12 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, C34.12 adds a risk adjustment factor of about 1.136 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.672 to 1.214 depending on the payment segment). A more severe related category (HCC 17, HCC 18, and HCC 19) supersedes it when both are reported. See the full factor table on the HCC 20 category page.
