Malignant transformation of an ovarian mature teratoma diagnosed 17 years ago: a case report and literature review of treatment with immune checkpoint inhibitors

A 69-year-old multiparous postmenopausal woman had undergone bilateral total hip arthroplasty 17 years ago. Computed tomography showed a mature teratoma of 10 cm in the pelvis. Subsequently, she presented with symptoms of hoarseness and weight loss, along with evidence of malignant transformation of the same tumor in the pelvis and multiple enlarged lymph nodes. Bilateral adnexectomy was performed via laparotomy, yet peritoneal dissemination persisted. The ovarian tumor's histopathological diagnosis was mature teratoma with squamous cell carcinoma. Additionally, the mediastinal lymph nodes biopsy revealed poorly differentiated carcinoma. Comprehensive genomic profiling testing of the ovarian tumor showed pathogenic variants of TP53 and PTEN, a high tumor mutational burden, homologous recombination deficiency and the absence of human papilloma virus. The similar genomic testing of the mediastinal tumor revealed three variants of uncertain significance that were common to the ovarian tumor. However, no variants of TP53 or PTEN were identified. Following surgery, she demonstrated a partial response to six cycles of conventional paclitaxel and carboplatin. She then received maintenance treatment with niraparib; however, disease progression subsequently occurred. The patient was treated with pembrolizumab and is currently receiving treatment with a partial response. Previous reports have demonstrated the efficacy of immune checkpoint inhibitors in 5 out of 6 cases of malignant transformation of mature teratomas, and this treatment appears to be a promising strategy.