ICD-10 Code G73.1 – Lambert-Eaton Syndrome in Neoplastic Disease (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G73.1 – Lambert-Eaton syndrome in neoplastic disease
What it is
G73.1 identifies Lambert-Eaton syndrome associated with an underlying neoplastic disease. It is used when the neuromuscular disorder is linked to cancer, not when the cause is uncertain.
Clinical signs
Typical findings include proximal muscle weakness, reduced or absent reflexes, and autonomic symptoms such as dry mouth. Clinical features vary; refer to documentation.
When to use this code
Use G73.1 when the provider documents Lambert-Eaton syndrome in the setting of a confirmed neoplasm. Code the malignancy separately when appropriate, and make sure the record supports the paraneoplastic association.
If the chart only says weakness, neuropathy, or suspected Lambert-Eaton syndrome, do not assume this code. Check documentation for the specific diagnosis and its relation to cancer.
Do not use for
Do not use this code for Lambert-Eaton syndrome without neoplastic disease, or for nonspecific muscle weakness. Check documentation.
Coding tip
Link G73.1 to the documented cancer only when the provider clearly states the paraneoplastic relationship.