Pineal Parenchymal Tumor of Intermediate Differentiation: two cases treated with adjuvant radiotherapy

Abstract

Background: Pineal parenchymal tumor (PPT) is a rare neoplasm arising from the pineal gland and originating from pineocytes. It accounts for 0.3% of all primary intracranial tumors. PPTs are classified as pineocytoma, pineocytoma with intermediate differentiation (PPTID) and pineoblastoma. PPTID is the least frequent type among these three. Little is known about its clinical behavior and the definitive treatment is yet to be defined. We presented two patients with PPTID managed in our institution with literature review. Case 1: A 65-year-old lady presented with increasing dizziness and vomiting in March 2008. CT brain noted an ill-defined lesion over the midbrain causing obstructive hydrocephalus. MRI revealed a heterogeneously enhancing lesion at the pineal region, superiorly abutting the posterior aspect of the thalamus and inferiorly extending to the cerebellum. Partial debulking of the tumor and a ventriculoperitoneal (VP) shunt were immediately performed. Pathology confirmed pineal parenchymal tumor of intermediate differentiation (PPTID), grade II – III. Patient then received post-op radiotherapy (RT) to the tumor bed using 3D conformal technique given 54Gy in 27 fractions over 5.5 weeks and completed in May 2008. She had good recovery after treatment. 6-month post-RT MRI showed significant improvement and decreased in size of the pineal tumor. The lesion remained static in 30-month post-RT MRI. Case 2: A 59-year-old lady presented with headache and unsteady gait since April 2009. MRI brain showed a ____ mass in the pineal region causing obstructive hydrocephalus. Maximal tumor resection with VP shunting was performed. Pathology confirmed PPTID. Patient subsequently had post-op RT to the tumor bed given 54Gy in 27 fractions over 5.5 weeks and completed treatment in August 2009. Interval post-RT MRIs and the latest one in April 2013 (Post-RT 45-month) still showed completion remission. Conclusion: PPTID is very rare and its proper management strategy remains unclear. Dose and volume of irradiation for PPT reported were heterogeneous and diverse, ranging from craniospinal irradiation, whole-brain RT, whole-ventricular RT to RT just to tumor bed. As shown in our cases, a less extended RT field to the tumor bed alone with dose up to brainstem tolerance would be reasonable and effective in view of the good radiosensitivity of PPTID and the minimum RT side effects. Further studies are warranted to investigate the best adjuvant treatment for PPTID.