A rare case of giant mediastinal tumor originating from lung tissue characterized by high fever and arrhythmia.

Background: Arrhythmias in patients with cancer are predominantly attributed to heart disease, anti-tumor drugs, and primary cardiac tumors. Arrhythmias directly induced by noncardiac primary tumors are rare. To date, there have been no reported cases of paroxysmal supraventricular tachycardia or sinus bradycardia caused by a posterior mediastinal tumor originating from the lung tissue.

Case Description: We present the case of a 65-year-old male diagnosed with a giant posterior mediastinal tumor originating from the lung tissue, A mediastinal lymph node biopsy was performed, and histopathological examination revealed a poorly differentiated adenocarcinoma of pulmonary origin. Based on the PET-CT and cranial enhancend MRI results, the posterior mediastinal tumor has a diameter exceeding 7 cm and has metastasized to the right hilar and mediastinal lymph nodes, with no distant metastasis observed. On the basis of these findings, the patient was diagnosed with stage IIIB mediastinal lung adenocarcinoma (cT4N3M0). The tumor measured 12.8 cm × 8.1 cm and could not be completely resected. Prior to immunochemotherapy, the patient experienced paroxysmal supraventricular tachycardia, followed by sinus bradycardia. After the first cycle of immunochemotherapy, the arrhythmia was corrected, and the body temperature returned to normal. However, the massive tumor led to malnutrition and various complications prior to the second cycle of treatment. Despite undergoing chemotherapy combined with immunotherapy, the patient's condition worsened, ultimately resulting in death. The overall survival period was 3 months.

Conclusion: This case report highlights the fact that a giant mediastinal lung adenocarcinoma can induce arrhythmias, which may manifest as supraventricular tachycardia or sinus bradycardia. Additionally, tumor fever also can induce elevated temperatures of 39 °C. Notably, giant posterior mediastinal tumors that are unsuitable for resection have a significantly poorer prognosis.