Therapeutic strategy for pineal parenchymal tumor of intermediate differentiation (PPTID): case report of PPTID with malignant transformation to pineocytoma with leptomeningeal dissemination 6 years after surgery.

Pineal parenchymal tumor of intermediate differentiation (PPTID) is rare. The WHO first classified PPTID in 2000 as a pineal parenchymal tumor (PPT) with an intermediate prognosis between pineocytoma (PC) and pineoblastoma (PB). It is considered an intermediate-grade tumor and divided into WHO grade II or III. The number of available reports about PPTID is presently limited, and the appropriate management for this tumor has not yet been determined. The authors report a rare case of PC in a 63-year-old woman who presented with lower-extremity weakness and gait disturbance. A pineal mass lesion was detected on MRI. A diagnosis of PC was established after microsurgical gross-total tumor resection, and the patient received no adjuvant therapy after surgery. Two years after surgery, a partial recurrence was recognized and Gamma Knife radiosurgery was performed. Fours years later, the patient developed diffuse leptomeningeal dissemination. She was successfully treated with craniospinal irradiation. Leptomeningeal dissemination may develop 6 years after the initial diagnosis of PC. A histopathological study of the recurrent tumor revealed a malignant change from PC to PPTID. The present case shows the importance of long-term follow-up of patients with PPTs following resection and the efficacy of craniospinal irradiation in the treatment of leptomeningeal dissemination.