Introduction Malignant transformation arising from ovarian mature cystic teratoma(MT-MCT) is very rare and has a poor prognosis. This study investigated clinical characteristics and prognosis of MT-MCT in a single institution.

Methods A retrospective chart review was performed. Patients diagnosed with MT-MCT at Haeundae Paik Hospital between 2010 and 2022 were identified.

Results Among 718 cases of ovarian MCT, malignant transformations were found in 11 patients (1.5%). The median age was 49 (range, 22–86) years. The mean size of MT-MCT was 11 (range, 4–22) cm. The most common symptom was abdominal discomfort, reported in seven(63.6%) cases, followed by urinary dysfunction in two(18.1%) cases. Tumor markers were elevated in preoperative examination and mainly included CA125(63.6%),CA19–9(36.3%),and SCCag(18.1%). Three patients underwent staging surgery, while eight patients underwent cystectomy or salpingo-oophorectomy without staging surgery. Five patients had squamous cell carcinoma, three had carcinoid, and three had other histological subtypes. Seven cases were in FIGO stage I, four cases were in stage II-IV. Patients in stage IC to IV received adjuvant chemotherapy and the overall 1-year survival rate was 33.3%. All the patients in stage IA survived until the period of follow up (mean survival time 51 months) except for one patient who died of old age.

Conclusion/Implications The possibility of MT-MCT was associated with large tumor size or advanced age. In cases of stage 1C or higher, the prognosis was worse compared to other types of ovarian cancer. Therefore, when encountering large tumor size or advanced age, it is important to consider the possibility of malignancy.