Background: The treatment of choice for Extra-osseous Ewing's sarcoma/primitive neuroectodermal tumor (ES/PNET), a rare neoplasm, is the VAC/IE regimen. This regimen includes Doxorubicin, Vincristine, Cyclophosphamide, Ifosfamide, and Etoposide, all of which have cardiotoxic effects. Myocarditis, a potentially threatening side effect following cancer therapy, can be accurately managed and diagnosed.

Case presentation: In the current study, we report the case of a 19-year-old female with a mass on the abdominal wall, diagnosed with ES/PNET. She was treated with the VAC/IE regimen. A month after the last session of chemotherapy, she experienced dyspnea. Upon evaluation, a high level of troponin and a low left ventricular ejection fraction (LVEF) were detected via transthoracic echocardiography. She was treated with anti-heart failure drugs, but the response was unsatisfactory. The possibility of Cancer therapy-related myocarditis was suspected, and cardiac magnetic resonance imaging (CMR) confirmed acute myocarditis. This patient exhibited a significant response to intravenous immunoglobulin (IVIG), with her LVEF improving from 30-35% to 50% within three months.

Conclusion: In this case, based on negative tests and the absence of viral signs and symptoms, Cancer therapy-related myocarditis is highly suspected as the cause of myocarditis. This case underscores the importance of accurately utilizing CMR as a non-invasive method for diagnosing myocarditis. It effectively highlights the identification of reversible myocarditis with appropriate treatment and the notable response to IVIG, suggesting its potential as a favorable treatment for myocarditis in younger patients.