High-grade sarcoma masquerading as growing teratoma syndrome after resection of ovarian immature teratoma: report of a case.

A thorough literature search revealed no previous reports of this entity, and we are the first to describe a case of a high-grade sarcoma arising from a recurrent immature teratoma misdiagnosed as growing teratoma syndrome. The patient was a 23-yr-old female, diagnosed at the age of 20 with a Stage IIIB immature ovarian teratoma. After surgery and chemotherapy, the patient developed multiple liver and pelvic masses that were diagnosed as mature teratomas based on small samples obtained by computed tomography-guided core biopsy. Three years after diagnosis the patient presented with severe respiratory difficulty and following resection, the final pathology revealed multiple tumors with foci of high grade sarcoma compatible with primitive neuroectodermal tumor/extraskeletal Ewing sarcoma based on morphology and immunohistochemistry (CD99, CD56). However, on the basis of further immunostaining and fluorescent in situ hybridization studies negative for rearrangement of EWSR1, the final pathologic diagnosis was high-grade unspecified (undifferentiated) sarcoma. This case illustrates the pitfalls of biopsying 1 site in a patient with recurrence of a heterogeneous tumor such as immature ovarian teratoma, especially when rendering a benign diagnosis such as growing teratoma syndrome. It is of utmost importance to adequately sample large-volume recurrent teratomas, and we suggest biopsying several different sites, to increase the likelihood of detecting a malignant component.