TY - JOUR AB - Merkel cell carcinoma (MCC) is a rare and highly aggressive neuroendocrine malignancy arising from mechanoreceptors in the basal epidermis. Due to a pronounced risk of spread and a high propensity for recurrence after treatment, immediate treatment is of utmost importance. Lambert‑Eaton myasthenic syndrome (LEMS) is a paraneoplastic phenomenon affecting the muscles with autoimmune pathophysiology, and >50% of known cases are associated with an underlying malignancy. In the present report, the case of a 67‑year‑old man presenting with progressive proximal muscle weakness, autonomic dysfunction and involuntary weight loss is described. Symptoms and detection of voltage‑gated calcium channel antibodies were consistent with LEMS. Distant metastases were found in the inguinal and iliac lymph nodes, and these were immunohistochemically confirmed to be of epithelial and neuroendocrine origin, consistent with MCC. Local radiotherapy and chemotherapy improved the symptoms; however, a change of treatment was required due to the side effects of the chemotherapy. Avelumab, an immune checkpoint inhibitor, was therefore introduced, and within a year the patient did not only experience tumor remission but also exhibited marked improvements in muscle strength and mobility. At present, 2 years later, the MCC is still in remission. To the best of our knowledge, the present report is the first to describe MCC with associated LEMS, which was successfully treated with avelumab after previous radiotherapy and chemotherapy, with both improved functional motor recovery and tumor reduction. In conclusion, the present case report demonstrated that the present treatment strategy is a potential treatment option and could thus be considered in similar cases. AD - Department of Clinical Sciences, Umeå University, SE‑90187 Umeå, Sweden Department of Medical Biosciences, Umeå University, SE‑90187 Umeå, Sweden Department of Oncology‑Pathology, Karolinska Institute, SE‑17177 Stockholm, Sweden Department of Radiation Sciences, Umeå University, SE‑90187 Umeå, Sweden AU - Green,Caroline AU - Mettävainio,Martin,Isaksson AU - Kjellman,Christina AU - Ramqvist,Torbjörn AU - Dalianis,Tina AU - Israelsson,Pernilla AU - Lindquist,David DA - 2022/11/01 DO - 10.3892/ol.2022.13513 IS - 5 JO - Oncol Lett KW - Lambert‑Eaton myasthenic syndrome Merkel cell carcinoma avelumab PY - 2022 SN - 1792-1074 1792-1082 SP - 393 ST - Combined treatment with radiotherapy, chemotherapy and avelumab results in regression of metastatic Merkel cell carcinoma and improvement of associated Lambert‑Eaton myasthenic syndrome: A case report T2 - Oncology Letters TI - Combined treatment with radiotherapy, chemotherapy and avelumab results in regression of metastatic Merkel cell carcinoma and improvement of associated Lambert‑Eaton myasthenic syndrome: A case report UR - https://doi.org/10.3892/ol.2022.13513 VL - 24 ER -