Teratoma With Malignant Ectomesenchymoma in the Pineal Region: A Case Report.

Tumors involving the pineal gland include germinomas, non-germinomatous, and parenchymal tumors. Sometimes these tumors can be differentiated into rhabdomyosarcoma, which is an aggressive and rapidly recurring sarcoma but is a rare event. We present the case of a 23-year-old male, with an eight-year-long history of a non-treated brain tumor compatible with a teratoma. Chemotherapy and radiotherapy were offered, and two years later, malignant transformation to astrocytoma, rhabdomyosarcoma, neural cell carcinoma, ganglioglioma, and low-grade chondrosarcoma was noted. Immunohistochemistry was valuable in differentiating these entities that confirmed the diagnosis. Malignant transformations may be secondary to the normal transformation of multipotent embryonic cells into more developed tissues after radiotherapy of teratoma and malignant ectomesenchymoma transformation.