LEMS Case Tied to Rare Subtype of Lung Cancer 

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by Patricia Inacio PhD |

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The recent case of a man with Lambert-Eaton myasthenic syndrome (LEMS) linked to a rare type of lung tumor, shows the condition can arise in patients with types other than small cell lung cancer.

The case report, “Pulmonary Large Cell Neuroendocrine Carcinoma Associated With Lambert-Eaton Syndrome,” was published in the journal Clinical Pathology.

LEMS is caused by the immune system wrongly launching an attack against calcium channels found in nerve cell endings, which are key to control muscle movement. As a result, patients experience muscle weakness, mostly in the lower limbs.

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Immunotherapy Did Not Worsen LEMS in Patient With Lung Cancer

The majority of LEMS cases are linked to an aggressive form of lung cancer known as small cell lung cancer (SCLC), with few cases reported in other types of lung cancer.

This report describes the case of a patient with LEMS associated with a rare, but highly aggressive, subtype of non-small cell lung cancer, called pulmonary large-cell neuroendocrine carcinoma (LCNEC).

The 69-year-old man complained of pain in his right eye, swollen and drooping upper eyelids (a condition called ptosis) five months prior to being admitted to the hospital. He had a past history of chronic obstructive pulmonary disease (COPD) due to heavy smoking.

He began experiencing progressive weakness in his legs. A neurological examination confirmed he had ptosis in both eyes and muscle weakness affecting both arms and legs. This was accompanied by a decrease in tendon reflexes.

Abnormal results of a repetitive nerve stimulation test confirmed the diagnosis of LEMS. This test uses electrodes to send small electrical pulses to measure a nerve’s ability of sending these signals to muscle tissues. Electrodes usually are placed on a patient’s skin over the muscles clinicians wish to test.

A chest X-ray showed the patient had a nodule in the inferior lobe of his right lung, which was confirmed by subsequent CT and PET scans. No signs of cancer spreading were found.

A biopsy of the tumor confirmed it was a LCNEC. The tumor was successfully removed upon surgical excision of the right lung’s inferior lobe.

According to the study authors, while the majority of LEMS cases are tied to an underlying SCLC, this case shows the disease also can occur in association with other rare types of lung cancer.

“LES [Lambert-Eaton syndrome] can present months or years before the identification of a lung neoplasm [tumor],” the authors wrote. “Symptoms of LES usually improve after tumor resection and treatment should be focused to the primary tumor.”