A 71-year-old man has been diagnosed with both Lambert-Eaton myasthenic syndrome (LEMS) and thymic small cell cancer in a rare case study linking the two conditions.
The study, titled “Thymic small cell carcinoma associated with Lambert–Eaton myasthenic syndrome,” appeared in The Annals of Thoracic Surgery.
Thymic small cell cancer is an extremely rare type of tumor that develops in the thymus, which is a specialized organ of the immune system that sits on top of the heart. The thymus is also where T cells mature.
LEMS has been linked to small cell lung carcinoma, but it is rarely associated with thymic small cell cancer. In fact, a Japanese team of investigators says no reports have been published about this association — that is, until their study.
These researchers described the case of 71-year-old man with a previous smoking history who had been referred to their hospital for a tumor in his mediastinum — the body cavity that separates the lungs from its surrounding organs. The man also complained of fatigue, drooping eyelids (ptosis), and gait disturbances for two months.
Imaging tests revealed a 2.7-cm mediastinal tumor at the front of his chest that had not spread to surrounding tissues. Further assessment showed the patient had below normal or absent reflexes, abnormal gait, trouble swallowing, and muscle weakness, which are all characteristic of myasthenia gravis. Laboratory analysis indicated LEMS and thymoma. Results of electromyography (a test that evaluates the condition of muscles and the nerve cells that innervate them) were consistent with the autoimmune disorder.
Based on their findings, doctors made a diagnosis of thymoma (meaning a tumor originating from the epithelial cells of the thymus) associated with Lambert-Eaton myasthenic syndrome. The diagnosis was made without resorting to a biopsy.
The 4.5-cm tumor was removed by performing a vertical line incision along the sternum or breastbone. Doctors confirmed the abnormal growth hadn’t spread to surrounding organs.
Further tissue and chemical analyses were compatible with the finding of very rare thymic small cell carcinoma.
A few reports indicated that the symptoms of LEMS-associated thymoma are eased after treatment, including surgery, but in this case, the patient’s symptoms did not improve following tumor removal, and he developed aspiration pneumonia three days after surgery.
Five days thereafter, anticholinesterase treatment (which improves muscle function) was administered, and the patient’s symptoms were alleviated. The man did not receive chemotherapy post-surgery, since the tumor appeared to have been totally resected.
“He remains in good health without any recurrence or progression of symptoms one year after surgery,” the authors wrote. “Additional cases are needed to clarify the clinicopathological [disease causing] features of thymic small cell carcinoma associated with LEMS.”