Papillary Tumor of the Pineal Region: Diagnosis and Treatment

Abstract

In 2003, papillary tumor of the pineal region has been described as a distinct entity on the basis of a series of six cases with identical histological features. It is a rare neuroepithelial tumor of the pineal region, characterized by a papillary architecture and epithelial cytology, with immunopositivity for cytokeratins, and ultrastructural features suggesting ependymal differentiation. It stains for vimentin, S100 protein, NSE, MAP2, N-CAM, and TTR, while GFAP labeling is focal or absent. Possible origin from specialized ependymal cells of the subcommissural organ has been suggested. In 2007, the World Health Organization (WHO) formally recognized it as a distinct entity in the classification of tumors of the nervous system. A specific WHO grade has not been given but it has been suggested that the tumor corresponds to grade II or III. However, histological grading criteria remain to be defined. Papillary tumor of the pineal region manifests in both children and adults. Its biological behavior is variable. Clinically, it is characterized by progressive growth, frequent local recurrence (which has been reported in up to 70% of the patients), and rare spinal dissemination (which has been reported in up to 7% of the patients). The 5-year estimates for overall survival and progression-free survival have been evaluated in 73 and 27%, respectively. At neuroimaging, the tumor appears as a well-circumscribed, contrast-enhancing pineal mass. At magnetic resonance imaging, a reliable finding seems to be the ­high-intensity signal on unenhanced T1-weighted images. When a mass of the posterior commissure or pineal region shows high-intensity signal on T1-weighted images, in the absence of fat, hemorrhage, melanin, or calcification, the diagnosis of a papillary tumor of the pineal region may be suggested so that specific immunohistochemical studies can be performed for a definitive diagnosis. Treatment of choice is surgery followed by irradiation, though the value of irradiation on disease progression is controversial. Incomplete resection and marked mitotic activity tend to be associated with recurrence and decreased survival.