Papillary tumour of the pineal region (2007 WHO Classification assigns a Grade II to III ).
Papillary tumour of the pineal region (PTPR) was newly added to the 2007 World Health Organization (WHO) classification of tumors of the central nervous system as a distinct pathological entity (1). Tumors of the pineal region are rare lesions that account for only 1% of all intracranial tumors (2). PTPR occurs most frequently in the third decade (4). Clinical presentation was mainly headache without focal neurological signs. The common features of PTPR on imaging are its well-circumscribed and cystic component and are usually measuring 0.5-5.0cm in diameter (3). Its intrinsic T1-hyperintensity can be explained by its secretory functions, resulting in the secretion of proteins and other T1-shortening products, which concentrate within the small cystic spaces seen within these tumors. The tumor's hyperintensity on T1-WI was emphasized by Chang et al. in order to distinguish it from other tumors that may occur in the pineal region (5).
PTPR is thought to arise from the specialized ependyma of the subcommissural organ (SCO) because the papillary structures of the PTPR mimic SCO cellular morphology (3). This tumour shares morphologic features with both papillary ependymoma and choroids plexus tumors. PTPR is characterized by an epithelial-like growth pattern in which the vessels are covered by layers of tumour cells forming perivascular pseudorosettes and their immunohistochemical profile is very similar to that of choroids plexus tumors (3). Pathological differential diagnosis of PTPR includes other pineal parenchymal tumors, papillary ependymomas, metastasis, and even papillary meningioma. Definitive diagnosis can be achieved by immunohistochemical staining and radiological correlation.(3). PTPRs generally expressed cytokeratin, neuron-specific enolase and S100. Immunoreactivity to EMA and synaptophysin was also reported and tended to be focal and patchy (10).
As a result of the rarity of these tumors, the natural history is incompletely known and data on treatment and the prognosis of PTPR remain scarce. A retrospective study by Fèvre-Montange et al. reported that local recurrence is frequent even after complete resection of PTPR and radiotherapy (3). Gross total resection was the only clinical factor that tended to be associated with overall survival and recurrence, though statistical significance was not achieved (3). Resection and/or radiotherapy for recurrent PTPR have been reported and, in some cases, are associated with stabilization of tumour progression (3). Chemotherapy and stereotactic radiosurgery have also been advocated (7, 8, 9). However, the value of these treatment modalities on disease progression in PTPR will need to be further investigated in prospective study.
Contributed by Yuen Shan Wong, Anthony Wing-Hung Chan, Ho Keung Ng, Danny Tat-Ming Chan, Daniel Wing-kit Ng, Deyond Yung-woon Siu, Peggy Tang, Wai-Sang Poon