G73.1 ICD-10-CM Code: Lambert-Eaton syndrome in neoplastic disease
G73.1 maps to CMS-HCC V28 196. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · free HCC coding tools
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FY 2026 Apr update / Diseases of the nervous system (G00-G99) / Diseases of myoneural junction and muscle (G70-G73)
G73.1
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceLambert-Eaton syndrome in neoplastic disease
Lambert-Eaton syndrome occurring as a complication of cancer. This is an autoimmune disorder affecting the connection between nerves and muscles, triggered by malignancy.
Buddy Insight
Lambert-Eaton syndrome in neoplastic disease is a paraneoplastic condition most commonly associated with small cell lung cancer, where cancer triggers an autoimmune attack on presynaptic calcium channels.
CMS-HCC V28
MappedHCC 196
Coefficient HCC 196: 0.516 (Community Non-Dual Aged (CNA))
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 115
Code-level coefficient reference
ESRD/PACE
MappedHCC 75
Code-level coefficient reference
RXHCC
MappedHCC 153
Code-level coefficient reference
Code Book Path
Inclusion Terms
OfficialNo inclusion terms are included in this display for G73.1. Check the code and parent instructions in the Code Book.
Excludes 2
Official- certain conditions originating in the perinatal period (P04-P96)Inherited from G00-G99
- certain infectious and parasitic diseases (A00-B99)Inherited from G00-G99
- complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from G00-G99
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Inherited from G00-G99
- endocrine, nutritional and metabolic diseases (E00-E88)Inherited from G00-G99
- injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from G00-G99
- neoplasms (C00-D49)Inherited from G00-G99
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from G00-G99
Related Codes
Includes
OfficialNo Includes notes are included in this display for G73.1. Check the code and parent instructions in the Code Book.
Excludes 1
Official- Lambert-Eaton syndrome not associated with neoplasm (G70.80-G70.81)
Code First
Official- underlying neoplasm (C00-D49)
Use Additional
OfficialNo Use Additional Code instructions are included in this display for G73.1. Check the code and parent instructions in the Code Book.
Code Also
OfficialNo Code Also instructions are included in this display for G73.1. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
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 G73.1 an HCC code?
Yes. G73.1 (Lambert-Eaton syndrome in neoplastic disease) maps to HCC 196, Myasthenia Gravis without (Acute) Exacerbation and Other Myoneural Disorders under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.516. 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: G73.1 is billable and maps to V28 HCC 196, Myasthenia Gravis without (Acute) Exacerbation and Other Myoneural Disorders. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- G73.1
- Description
- Lambert-Eaton syndrome in neoplastic disease
- HCC (V28)
- HCC 196 — Myasthenia Gravis without (Acute) Exacerbation and Other Myoneural Disorders
- RAF reference coefficient
- 0.516
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
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 G73.1 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for G73.1
For G73.1, 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
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What This Code Means
G73.1 is the ICD-10-CM diagnosis code for lambert-eaton syndrome in neoplastic disease. Lambert-Eaton syndrome occurring as a complication of cancer. This is an autoimmune disorder affecting the connection between nerves and muscles, triggered by malignancy. G73.1 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering diseases of myoneural junction and muscle (g70-g73).
Under the CMS-HCC V28 risk adjustment model, G73.1 maps to Myasthenia Gravis without (Acute) Exacerbation and Other Myoneural Disorders (HCC 196) with a source-labeled community, non-dual, aged reference coefficient of 0.516. No V24 mapping is shown for G73.1; 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.
Always code the underlying neoplasm first, followed by this code to show the relationship between cancer and the syndrome. For G73.1, 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 G73.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Always code the underlying neoplasm first, followed by this code to show the relationship between cancer and the syndrome
- •Document the type of cancer and whether it is small cell lung cancer, which is the most common association
Clinical Significance
Lambert-Eaton syndrome in neoplastic disease is a paraneoplastic condition most commonly associated with small cell lung cancer, where cancer triggers an autoimmune attack on presynaptic calcium channels. This diagnosis indicates both malignancy and a significant neurological complication, reflecting extremely complex patient care. Capturing this code alongside the underlying malignancy is critical for accurate risk adjustment.
Documentation Requirements
- ✓Documentation of the underlying neoplasm (most commonly small cell lung cancer)
- ✓Clinical features of Lambert-Eaton syndrome: proximal weakness, autonomic dysfunction, hyporeflexia
- ✓Electrodiagnostic confirmation: incremental response on repetitive nerve stimulation
- ✓Voltage-gated calcium channel antibody testing results
- ✓The underlying neoplasm code must be sequenced first
- ✓Provider's explicit documentation linking the Lambert-Eaton syndrome to the malignancy
Commonly Confused Codes
- •G70.80: Lambert-Eaton syndrome, unspecified is for cases without an identified underlying disease
- •G70.81: Lambert-Eaton syndrome in disease classified elsewhere is for non-neoplastic underlying diseases
- •G70.00: Myasthenia gravis without exacerbation is a different autoimmune neuromuscular disorder
- •G73.3: Myasthenic syndromes in other diseases is for secondary myasthenic symptoms, not Lambert-Eaton syndrome