Stage IV malignant transformation of mature cystic teratoma palliatively treated with concurrent chemoradiotherapy: A case report.

Background: Malignant transformation (MT) of mature cystic teratoma (MCT) has a poor prognosis, especially in advanced cases. Concurrent chemoradiotherapy (CCRT) has an inhibitory effect on MT.

Case Summary: Herein, we present a case in which CCRT had a reduction effect preoperatively. A 73-year-old woman with pyelonephritis was referred to our hospital. Computed tomography revealed right hydronephrosis and a 6-cm pelvic mass. Endoscopic ultrasound-guided fine-needle biopsy (EUS-FNB) revealed squamous cell carcinoma. The patient was diagnosed with MT of MCT. Due to her poor general condition and renal malfunction, we selected CCRT, expecting fewer adverse effects. After CCRT, her performance status improved, and the tumor size was reduced; surgery was performed. Five months postoperatively, the patient developed dissemination and lymph node metastases. Palliative chemotherapy was ineffective. She died 18 months after treatment initiation.

Conclusion: EUS-FNB was useful in the diagnosis of MT of MCT; CCRT suppressed the disease and improved quality of life.