Pineal Anlage Tumor: Case Report and Review of Literature

The pineal gland is a midline organ located posterior to the third ventricle in the quadrigeminal cistern. It is surrounded by the splenium of the corpus callosum above, the thalami laterally, and the quadrigeminal plate and vermis below, together delineating the pineal region [1]. Histologically, the human pineal gland parenchyma is mainly composed of pineocytes with a few supportive astrocytes, is subdivided into lobules imparting a glandular appearance, and is invested by leptomeninges [2]. Lesions of the pineal region are occasionally encountered, and may be non-neoplastic (i.e. pineal cysts) or neoplastic. Pineal neoplasms are relatively rare, accounting for 3-8% of pediatric and less than one percent of adult brain tumors [3]. Pineal region tumors are a heterogenous group of neoplasms, owing to the presence of various cell types present in a small region that can each undergo neoplastic transformation. Germ cell tumors are the most common tumors of the pineal region. Ependymomas, astrocytomas (both localized and diffuse), choroid plexus neoplasms, and meningiomas also may occur, but are much less common. Neoplasms unique to this region are presumed to arise from pineocytes, the resident synaptophysinpositive neuroepithelial cells of the pineal gland. These “pineal parenchymal neoplasms” span a spectrum of biologic aggression, with pineocytomas and pineoblastomas showing the least and most aggressive clinical courses, respectively. Of the tumors unique to the pineal region, the pineal anlage shows the most unusual pathologic features, and is extremely rare. Although not officially recognized as a stand-alone entity by the World Health Organization (WHO), the 2007 WHO Classification of Tumours of the Central Nervous System describes pineal anlage tumors as rare pineoblastomas with melanin production and cartilaginous and/or rhabdomyoblasticdifferentiation [4-6]. Pineal anlage tumors were first described by Schmidbauer and colleagues in 1989 as a pineal region tumor in a 9-year-old girl that exhibited neuronal, retinoblastic and ectomesenchymal differentiation [7]. In the following years, only six other cases of pineal anlage tumors showing the described pathologic features have been reported [6-11]. These tumors showed variable pathologic findings, including primitive neuroepithelial proliferations, neural rosettes, skeletal muscle, pigmented cells, and cartilage. Olaya described a case of a pineal anlage tumor in a 5-monthold boy treated at our institution in 2010 [6]. We report the clinical presentation, neuroradiologicfindings, histopathology, and immunophenotype of a second case of pineal anlage tumor treated at our institution.