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.

Key words: Pinealoma, Carcinoma, papillary, Immunohistochemistry, Pathology

摘要： 研究背景 松果体区乳头状肿瘤是世界卫生组织于2007 年新定义和描述的一种少见的中枢神经系统神经上皮组织肿瘤，可能起源于下连合器的特殊室管膜细胞。组织学以胞质宽大、胞界清楚的柱状上皮样肿瘤细胞排列成乳头状或实体片状结构为特点。因缺乏特征性临床和影像学表现，术前明确诊断困难且极易误诊。本文报告1 例典型的松果体区乳头状肿瘤患者的临床病理学特征，以期提高对该病的鉴别诊断能力。方法与结果 男性患者，57 岁，头痛6 个月、加重1 个月入院。MRI 显示幕上中线松果体区和第三脑室界限清楚的占位性病变，呈高信号，增强后病灶均匀强化。术中可见病灶位于松果体区，突入第三脑室，无囊性变，无包膜，与周围组织界限清楚，手术全切除。肿瘤组织由乳头状结构和实体片状区域构成，乳头状结构含明显的纤维血管轴心，周围包绕数层柱状上皮样肿瘤细胞，大小形态较一致，均富嗜酸性胞质，界限清楚；实体片状区域细胞排列较密集，可见围血管“假菊形团”和室管膜“菊形团”结构，肿瘤细胞浸润周围脑实质。肿瘤细胞广谱细胞角蛋白和S-100 蛋白呈弥漫强阳性，胶质纤维酸性蛋白和上皮膜抗原呈阴性。术后未予药物化疗和放射治疗，随访1 年，肿瘤未复发。结论 松果体区乳头状肿瘤是中枢神经系统鲜见病变，由于缺乏特征性影像学表现，以及组织学形态与其他乳头状肿瘤相似，术前难以明确诊断且在鉴别诊断时有一定困难。临床应提高对松果体区乳头状肿瘤的警惕性，并注意与其他具有相似组织学构象的中枢神经系统原发性或转移性肿瘤相鉴别。

关键词: 松果体瘤, 癌, 乳头状, 免疫组织化学, 病理学