2026 ICD-10-CM Diagnosis Code G73.1Lambert-Eaton syndrome in neoplastic disease

ICD-10-CM Codes›G00–G99›G70-G73›G73

ICD-10-CM G73.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

G73.1 is a billable ICD-10-CM diagnosis code for Lambert-Eaton syndrome in neoplastic disease. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). The code is not accepted as a principal diagnosis by the Medicare Code Editor and a manifestation code that cannot be reported as the principal diagnosis. Coders also document this condition as eaton Lambert syndrome with underlying malignancy. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Conditions due to neoplasm or the treatment of neoplasm and Myopathies.

Code Identity

ICD-10-CM Code
G73.1
Billable Status
Yes — Valid for Submission
Code Describes
Lambert-Eaton syndrome in neoplastic disease
Short Description
Lambert-Eaton syndrome in neoplastic disease
Same as the full description in the CMS dataset.
Parent Code
G73
Disorders of myoneural junction and muscle in diseases classified elsewhere

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG70-G73Diseases of myoneural junction and muscle
CategoryG73Disorders of myoneural junction and muscle in diseases classified elsewhere
This CodeG73.1Lambert-Eaton syndrome in neoplastic disease

Code EditsBilling

Medicare Code Editor checks that affect claim validity for G73.1.

Manifestation diagnoses
Manifestation codes describe the manifestation of an underlying disease, not the disease itself, and therefore should not be used as a principal diagnosis.
Unacceptable principal diagnosis
There are selected codes that describe a circumstance which influences an individual's health status but not a current illness or injury, or codes that are not specific manifestations but may be due to an underlying cause. These codes are considered unacceptable as a principal diagnosis.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Eaton Lambert syndrome with underlying malignancy
  • Eaton-Lambert syndrome

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Code First

Type 1 Excludes

  • Lambert-Eaton syndrome not associated with neoplasm G70.80 G70.81

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Syndrome
      • Lambert-Eaton
        • in
          • neoplastic disease

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR NEO074
Conditions due to neoplasm or the treatment of neoplasm
Default principal diagnosis: inpatient No · outpatient No
CCSR NVS018
Myopathies
Default principal diagnosis: inpatient No · outpatient No

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Convert G73.1 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
358.31 Lambert-Eaton synd neopl
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About G73.1Overview

Is G73.1 a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report Lambert-Eaton syndrome in neoplastic disease on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Can G73.1 be a principal diagnosis?

No. This is a manifestation code: Lambert-Eaton syndrome in neoplastic disease describes the manifestation of an underlying disease rather than the disease itself, so the underlying condition is sequenced first.

What is the ICD-9 equivalent of G73.1?

Under the General Equivalence Mappings, Lambert-Eaton syndrome in neoplastic disease converts to ICD-9-CM 358.31 (Lambert-Eaton synd neopl). The mapping is a direct match.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.