Papillary tumor of the pineal region: two case studies and a review of the literature.

Papillary tumor of the pineal region (PTPR) is a newly recognized distinct entity in the 2007 World Health Organization nomenclature. This tumor is characterized by epithelial-appearing areas with papillary features and more densely cellular areas that often display ependymal-like differentiation. Ultrastructurally, this rare neuroepithelial tumor possesses neuroendocrine, secretory, and ependymal organelles that likely originate from the subcommissural organ (SCO) near the aqueduct of Sylvius. To date, approximately fifty-seven described cases worldwide have been recognized, with ages ranging from 5 years to 66 years (mean age=32 years). Clinical presentation most often includes headache and obstructive hydrocephalus. The tumor, which is well circumscribed, may be cystic and radiographically is often considered to be consistent with the findings of a pineocytoma. Microscopic evaluation often demonstrates a lesion with papillary areas lined by epithelioid tumor cells with eosinophilic cytoplasm and more cellular areas with cells exhibiting clear or vacuolated cytoplasm. Perivascular and true rosettes may be identified. Distinctive immunohistochemical features including reactivity for keratins (AE1/AE3, CAM 5.2, CK18) and only focal GFAP staining help distinguish this neoplasm from an ependymoma. The relative paucity of data compiled for this tumor makes giving an accurate diagnosis and prognosis a daunting task. We discuss two additional cases of PTPR that presented to us within a three-month span in order to more fully elucidate the possible presentations of this rare entity. Furthermore, we examine now 59 reported cases of PTPR in order to review the current diagnostic and treatment modalities in addition to exploring emerging research encompassing this unusual neoplasm.