Risk factors for malignant transformation of mature cystic teratoma.

Objective: The aim of this study was to investigate the preoperative characteristics of benign mature cystic teratoma (MCT) and struma ovarii and their risk factors associated malignancies, and determine the appropriate treatment options for these tumors.

Methods: This was a retrospective study on 248 patients who were pathologically diagnosed with ovarian MCT, struma ovarii, or malignant transformations of these tumors at Inje University Haeundae Paik Hospital from March 2010 to January 2015. Routinely evaluated results of adnexal masses before surgery were compared.

Results: A total of six patients (2.4%) were confirmed to have malignant tumors. Of the struma ovarii patients, two out of five patients (40%) were confirmed to have malignancy. The mean age at the diagnosis of patients with malignant transformation of teratomas was 43.0 years (range, 27 to 67 years), which was higher than that of patients with benign teratomas (36.5 years). The mean diameter of the tumor before surgery in the malignant tumor group was 11.4 cm and larger than 6.5 cm of benign group (P=0.003). The mean CA-125 level in the malignant tumor group was higher than that in the benign tumor group (P=0.01).

Conclusion: Risk factors for malignant transformation of MCT include elevated CA-125 levels, older age, large tumor masses, and postmenopausal status.