2027 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 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

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 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 56 through 57. 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 72 closely related codes. 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.

For Medicare Advantage risk adjustment, G73.1 maps to CMS-HCC Category 196 (Myasthenia Gravis without (Acute) Exacerbation and Other Myoneural Disorders) under the V28 model, adding a risk factor of about 0.516 for a community, non-dual, aged beneficiary in payment year 2027.

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.

Medicare Risk Adjustment (HCC)Billing

G73.1 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.

CMS-HCC V28 Category (Payment Model)
HCC 196— Myasthenia Gravis without (Acute) Exacerbation and Other Myoneural Disorders
Payment HCC · PY 2027 one of 9 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+0.516
community, non-dual, aged · ranges 0.248–0.642 across segments
Hierarchy
Superseded by HCC 195
a more severe related category takes the payment when both are reported
Prior Model (CMS-HCC V24)
HCC 75
V24 retired V28 pays 100% of MA risk scores since PY 2026
Other CMS Models
PACE (CMS-HCC V22): HCC 75 · ESRD (V21): HCC 75 · ESRD (V24): HCC 75
ESRD V21 weights: 0.059 dialysis, 0.284–0.323 functioning graft · ESRD V24 weights: 0.074 dialysis, 0.344–0.599 functioning graft
Part D (RxHCC)
RxHCC 153 — Myasthenia Gravis and Other Myoneural Disorders
also risk-adjusts in the Part D prescription drug model (V08)

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.

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

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to G73.1: its own notes plus those printed at Chapter 6. A note printed at a category, block or chapter applies to every code under it.

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

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

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 6 (G00-G99) Diseases of the nervous system applies to 700 codes
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Code First

The underlying condition named in the note is sequenced before this code.

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name G73.1, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming G73.1: they are not reported together with it, unless the two conditions are unrelated.

  • G70.81 Lambert-Eaton syndrome in disease classified elsewhere
    Lambert-Eaton syndrome in neoplastic disease (G73.1)

Code First 1

These codes say to code first a condition named in the note, and G73.1 is one of the conditions named.

  • M62.84 Sarcopenia
    disorders of myoneural junction and muscle disease in diseases classified elsewhere (G73.-) names G73.-, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About G73.1Overview

What is the ICD-10 code for Lambert-Eaton syndrome in neoplastic disease?

The ICD-10-CM code for Lambert-Eaton syndrome in neoplastic disease is G73.1 (sometimes written as G731). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

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, 2026 through September 30, 2027.

What MS-DRG does G73.1 group to?

On inpatient claims, Lambert-Eaton syndrome in neoplastic disease maps to MS-DRG 57, 56, with relative weights from 1.2835 to 2.2649 depending on complications. Higher weights mean higher Medicare reimbursement.

Is G73.1 a CC or MCC?

CMS lists G73.1 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 72 closely related codes in its exclusion list.

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 HCC is G73.1?

G73.1 (Lambert-Eaton syndrome in neoplastic disease) maps to CMS-HCC Category 196 (Myasthenia Gravis without (Acute) Exacerbation and Other Myoneural Disorders), commonly written as HCC 196, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 75 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 153.

Does G73.1 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, G73.1 adds a risk adjustment factor of about 0.516 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.248 to 0.642 depending on the payment segment). A more severe related category (HCC 195) supersedes it when both are reported. See the full factor table on the HCC 196 category page.