Tehran University of Medical Sciences Basic & Clinical Cancer Research 2228-6527 14 3 2023 09 30 151 154 Maryam Naseri Department of Pediatrics, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran. Amir Mohamad Hashem Asnaashari Lung Disease Research Center, Mashhad University of Medical Science, Mashhad, Iran Shahabaddin Sorouri 3. Internal Department, Mashhad University of Medical Sciences, Mashhad, Iran 2022 11 28 2023 05 13 Lung cancer is the deadliest type of cancer in the world, and small cell lung cancer (SCLC) is one of the most fatal types of relevant tumors. The aim of this report was to describe the status of a patient presenting with progressive weakness, who did not have a previous medical history. Clinical examination revealed bilateral edema of the lower limbs. Lab results exhibited severe hypokalemia and metabolic alkalosis. physical examination showed elevated blood pressure. Imaging revealed a large mass with necrosis. Bronchoscopy was done and biopsy pathology showed SCLC. The patient underwent chemotherapy with cisplatin and etoposide. Following SCLC, the patient developed a type of paraneoplastic syndrome called Cushing syndrome. He experienced a severe decrease in saturation in the second session of chemotherapy and eventually died. With respect to the fact that most paraneoplastic syndromes are associated with poor response to treatment, high clinical suspicion is essential for the rapid diagnosis of these syndromes to improve outcomes. https://bccr.tums.ac.ir/index.php/bccrj/article/view/456