A case series of transformation of teratoma to primitive neuroectodermal tumor: evolving management of a rare malignancy.

Primitive neuroectodermal tumor (PNET) is a pathologic diagnosis that encompasses several different tumor types, including central nervous system tumors and Ewing's sarcomas. Teratoma, a common element of germ cell tumor (GCT), has the ability to transform to malignant PNET in a small number of patients. Making a definitive diagnosis of PNET is difficult given its deviation from elements of GCT and its non-specific pathologic findings. Establishing the diagnosis is crucial as PNETs respond poorly to standard platinum-based chemotherapy used for treatment of GCT. Primary treatment for PNET is surgical, though this is often not feasible in many patients due to extensive disease at diagnosis. As an alternative, chemotherapy regimens traditionally used for Ewing's sarcoma, such as vincristine, doxorubicin and cyclophosphamide alternating with ifosfamide and etoposide, have shown limited efficacy in the neoadjuvant, adjuvant, and palliative settings. Future research should delineate the genetic underpinnings of PNET and develop therapeutic options accordingly.