Clinicopathological characteristics of papillary tumor of the pineal region

Abstract

Background Papillary tumor of the pineal region (PTPR) is a newly recognized distinct entity in the 2007 WHO nomenclature. This tumor is characterized by epithelial-appearing areas with papillary features and more densely cellular areas that often display ependymal-like differentiation, which is likely to originate from the specialized ependymocytes of subcommissural organ near the Sylvian cerebral aqueduct. Due to its rarity and non-specific appearance in radiological exanimation, it is a diagnostic challenge for radiologists and histopathologists to differentiate PTPR from other primary or metastatic lesions located in the pineal region because of their similarities in radiological and histological findings. The aim of this study is to summarize the clinicopathological features of PTPR and discuss the differential diagnosis of histologically similar papillary tumors in pineal region.  Methods The clinical manifestations of a patient with PTPR occurring in supratentorial pineal region were presented retrospectively. Resected mass was routinely paraffin-embedded and stained with hematoxylin and eosin. Dako EnVision immunohistochemical staining system was used to detect the tumor antigen expressions, including vimentin (Vim), glial fibrillary acidic protein (GFAP), S-100 protein (S-100), pan cytokeratin (PCK), cytokeratin 7 (CK7), CK20, epithelial membrane antigen (EMA), neuronal nuclear antigen (NeuN), synaptophysin (Syn), neuron-specific enolase (NSE), and Ki-67 labeling index (MIB-1).  Results A 57-year-old male patient presented with 6-month history of mild headache, and became severe in last one month. MRI revealed a solid well-circumscribed lesion in supratentorial midline near the pineal region and the posterior third ventricle with mild heterogeneous enhancement. Craniotomy was performed and the tumor was removed totally. Histological examination revealed that the lesion contained papillary areas lined by columnar epithelioid tumor cells with eosinophilic cytoplasm and more cellular areas with cells exhibiting clear or eosinophilic cytoplasm. Perivascular pseudorosettes and ependymal rosettes may be identified. The tumor cells were observed to invade the surrounding brain parenchymal. Immunohistochemical staining showed that the tumor cells were diffusely positive to Vim, PCK and S-100, but negative to GFAP, EMA, CK7 and CK20. Syn and NSE were observed to be focally weak positivity. Ki-67 labeling index was approximately 5%. Based on clinical presentations and histological findings, a final histological diagnosis of PTPR, WHO grade Ⅱ-Ⅲ, was made according to the criteria of WHO classification. The patient did not receive chemotherapy or radiotherapy, and was followed-up for 12 months, without any neurological deficit or signs of recurrence.  Conclusions PTPR is a rare tumor of central nervous system with aggressive clinical behaviors. Due to the relative paucity of reported cases of PTPR, its natural history is unknown. Histological grading criteria remain undefined, and the prognosis of tumor is uncertain. Due to similarities in histological findings, it may be difficult to differentiate PTPR from other primary or metastatic tumors with prominent papillary feature occurring in central nervous system. Thorough inspection under the microscopy and appropriate immunohistochemical profile are necessary for correct diagnosis.

doi: 10.3969/j.issn.1672-6731.2014.07.010