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ICD-10-CM C34.90: Malignant neoplasm of unspecified part of unspecified bronchus or lung

C34.90 is the billable ICD-10-CM code for malignant neoplasm of unspecified part of unspecified bronchus or lung, in category C34 (Malignant neoplasm of bronchus and lung) of the Malignant neoplasms of respiratory and intrathoracic organs section. As a principal diagnosis it groups to MS-DRG 180 Respiratory Neoplasms with MCC, MS-DRG 181 Respiratory Neoplasms with CC, MS-DRG 182 Respiratory Neoplasms without CC/MCC (MDC 04 MDC 04: Diseases and Disorders of the Respiratory System). It maps to HCC 20 (Lung and Other Severe Cancers) in CMS-HCC V28. As a secondary diagnosis it is a CC, excluded with 26 principal diagnoses. 56 LCD billing and coding articles list it as covered.

Compiled from CMS files by the QuickIntell RCM Editorial Team · Data effective · Method: reference methodology · Report a data correction

Data currency: ICD-10-CM code descriptions: FY2027 (effective October 1, 2026); IPPS Table 5 (MS-DRG weights): v44 FY2027 (final rule + CN3) (effective October 1, 2026); ICD-10-CM to HCC mapping: PY2027 initial ICD-10-CM mappings (dates of service 2026) (payment year 2027); Medicare Coverage Database billing and coding articles: MCD release October 8, 2026 (effective October 4, 2026). Next CMS release: FY2028 code files, effective October 1, 2027 for the ICD-10-CM code descriptions; FY2028 final rule (August 2027), effective October 1, 2027; an April 1 interim grouper update when CMS issues one for the IPPS Table 5 (MS-DRG weights); PY2028 advance notice (February 2027) and the PY2027 midyear final mapping (spring 2027) for the ICD-10-CM to HCC mapping; weekly, every Thursday for the Medicare Coverage Database billing and coding articles.

Code
C34.90
billable FY2027 ICD-10-CM code
Category
C34 Malignant neoplasm of bronchus and lung
Chapter
2: Neoplasms (C00-D49)
CC/MCC (MS-DRG v44)
CC
CMS-HCC V28
HCC 20
POA reporting
Required

Tabular list notes for C34.90

Inclusion terms
  • Lung cancer NOS

Inherited from C34 (Malignant neoplasm of bronchus and lung)

Excludes1 (never coded together)
  • Kaposi's sarcoma of lung (C46.5-)
  • malignant carcinoid tumor of the bronchus and lung (C7A.090)
Use additional code
  • code to identify:
  • exposure to environmental tobacco smoke (Z77.22)
  • exposure to tobacco smoke in the perinatal period (P96.81)
  • history of tobacco dependence (Z87.891)
  • occupational exposure to environmental tobacco smoke (Z57.31)
  • tobacco dependence (F17.-)
  • tobacco use (Z72.0)

MS-DRG grouping when C34.90 is the principal diagnosis

MS-DRG v44 groups for C34.90 as principal diagnosis
MDCMS-DRGs
04 MDC 04: Diseases and Disorders of the Respiratory System180181182

The final group also depends on procedures, secondary diagnoses and discharge status; the MS-DRG lookup for C34.90 shows the full grouping logic.

CC/MCC status and inpatient edits

As a secondary diagnosis, C34.90 is a CC under MS-DRG v44, unless the principal diagnosis is one of the 26 codes in its exclusion list. Check C34.90 against a principal diagnosis.

  • Present on admission: a POA indicator is required on inpatient claims.

CMS-HCC V28 risk adjustment

In the PY2027 mapping, C34.90 maps to HCC 20 (Lung and Other Severe Cancers). The HCC lookup shows the RAF weight and the hierarchy.

LCD billing and coding articles that list C34.90

56 current Medicare billing and coding articles list C34.90 among the diagnoses that support medical necessity for the services they cover.

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Frequently asked questions

What does ICD-10-CM C34.90 mean?

C34.90 means malignant neoplasm of unspecified part of unspecified bronchus or lung. The tabular list also files these terms under it: Lung cancer NOS. It is one of 16 billable codes under C34, malignant neoplasm of bronchus and lung.

Which MS-DRG does C34.90 group to?

As the principal diagnosis, C34.90 groups to MS-DRG 180 Respiratory Neoplasms with MCC, MS-DRG 181 Respiratory Neoplasms with CC, MS-DRG 182 Respiratory Neoplasms without CC/MCC (MDC 04 MDC 04: Diseases and Disorders of the Respiratory System) under MS-DRG v44, before procedures and secondary diagnoses are applied.

Does C34.90 map to an HCC?

Yes: HCC 20, Lung and Other Severe Cancers, in the PY2027 CMS-HCC V28 mapping.

Is C34.90 a CC or MCC?

C34.90 is a CC under MS-DRG v44; 26 principal diagnoses exclude it.

Sources

Every figure on this page is taken from the CMS publications below, as released by the Centers for Medicare & Medicaid Services. Projection built 2026-10-10. Verify against the primary file before billing or contracting decisions. The reference methodology explains how each figure is computed from these files.

Disclaimer

The descriptor and notes are reproduced from the FY2027 ICD-10-CM files; MS-DRG, CC/MCC and HCC facts come from the CMS FY2027 and PY2027 tables. Code from the medical record and the ICD-10-CM Official Guidelines. Not legal, clinical or billing advice.

Found a figure that does not match the CMS file? Report a data correction with the CMS file and the value you expected; the request reaches the editorial team through the contact form.