Malignant transformation of ovarian teratoma responded well to immunotherapy after failed chemotherapy: a case report.

Mature cystic teratomas (MCTs), also known as dermoid cysts, are the most common ovarian germ cell tumors and the most common ovarian neoplasms in patients younger than 20 years. MCTs mainly appear as pelvic masses that are made up of different types of well differentiated derivates of at least two germinative cell types. MCT of the ovary is always benign lesions with slow growth and good prognosis. Unfortunately, in about 1-2% of cases, it may undergo malignant transformation. At present, surgical treatment is the preferred option for the early stage of malignant transformation of teratomas, while with a high postoperative recurrence rate. For advanced or recurrent malignant ovarian teratomas, the effect of conventional chemotherapy or radiotherapy is poor, leading to high mortality. Thus, identifying novel treatment for malignant transformed MCTs is an urgently need in clinic. Recently, PD-1 antibody-based immunotherapy has achieved great success in treatment of lung cancer, melanoma, and other malignant tumors. However, its effect on the malignant transformation of ovarian teratomas has not yet been reported. Here we reported a patient who suffered malignant transformation of ovarian teratoma and responded well to camrelizumab, an anti-PD-1 inhibitor.