Aggressive Chondroblastic Osteosarcoma Arising in a Mature Cystic Teratoma: A Case Report and Literature Review

Abstract

Mature cystic teratoma (MCT) is the most common ovarian germ cell tumor with a typically excellent prognosis. Malignant change in a somatic component of an MCT is rare, occurring in approximately 1% of cases, and most commonly occurs in the sixth to seventh decades. Osteosarcoma arising within an MCT is exceedingly rare, with only seven previously reported cases. The median age affected is 54 years. At presentation, the tumor is often large with intra-abdominal metastases. The prognosis is dismal, with only one long-term survivor. We are reporting on the clinical, radiographic, and cytohistologic features of the eighth documented case of an osteosarcoma arising in an MCT. A 29-year-old female with a medical history of scimitar syndrome (partial anomalous pulmonary venous return) presented to the emergency room with pelvic pain concerning for ovarian torsion. Computed tomography showed a 14-cm cystic, solid, and fatty mass of the left ovary consistent with an atypical dermoid cyst. She underwent laparoscopic surgery notable for filmy adhesions and friability of the mass. Microscopically, the cyst was composed of dermal elements while the solid component demonstrated lobules of malignant cartilage in addition to osteoid production. The tumor cells stained positively for SATB2 and vimentin and were negative for EMA, cytokeratin AE1/AE3, S100, SALL4, PLAP, and OCT3/4. The abdominal fluid was positive for bizarre malignant cells that were strongly SATB2 positive. A subsequent PET scan highlighted extensive metastatic peritoneal deposits. The patient received one round of chemotherapy before dying 46 days after diagnosis. Osteosarcoma arising in an MCT is a rare and aggressive malignancy with almost all cases resulting in death within months after diagnosis. While not entirely specific, SATB2 immunohistochemistry in conjunction with cytohistomorphology can aid in making the correct diagnosis, particularly in cytologic specimens where background tumor matrix is not present.