Clear cell ependymoma

Abstract

Four cystic brain tumours, one from the frontal lobe, one in the third ventricle and two in the cerebellum, were studied histologically including immunostaining and electron microscopy. Anatomically, all the tumours were located within or adjacent to the ventricular system. By light microscopy, the tumours had a largely honeycomb pattern and were made up of clear cells. Some of the clear cells showed positive for GFAP. Leu 7, Factor VIII and NSE were negative. Electron microscopy of the areas with clear cells revealed densely packed polyhedral cells with clear cytoplasm. They had well developed intercellular junctions, microvilli and some cilia which confirmed their ependymal derivation. Perivascular pseudorosettes or papillary features were only seen in limited areas, where GFAP was strongly positive in the tumour cell processes. As these tumours mimic oligodendroglioma and cerebellar haemangioblastoma, they are called as "clear cell ependymoma" to obviate such errors in diagnosis.

Clear cell ependymoma with trisomy 19 developing bone metastases

“…Ependymomas vary considerably in both their morphologic appearance and their biologic behavior. A rare subtype is the clear cell ependymoma which was first described in 1983 [9] and named "clear cell ependymoma" by the same authors in 1989 [10]. It is characterized by oligodendroglia-like appearance with chicken-wire vessels, sheets of uniform cells with rounded nuclei and encircling, perinuclear, clear halos [11,12], some authors gave the threshold of 50% of those clear cells to define clear cell ependymoma [12].…”

Intraparenchymal clear cell ependymoma

“…[2] Subsequently, they encountered three more similar cases, which they termed as ‘clear cell ependymoma’. [2] CCE was subsequently included in the World Health Organization classification in 1993, as a distinct variant.…”

Clear Cell Ependymoma of the Temporal Lobe in a Child: A Case Report

“…Ependymal rosettes and/or perivascular pseudorosettes help establish the correct diagnosis [1]. However, not all cases show these characteristics [2, 6, 15, 16]. In our case, there were pseudorosette formations, but no true rosettes.…”

“…Clear cell appearance causes misdiagnosis of these tumors as oligodendroglioma, pilocytic astrocytoma, central neurocytoma, hemangioblastoma or metastasis of renal cell carcinoma [1,2,3, 6, 21]. Ependymal rosettes and/or perivascular pseudorosettes help establish the correct diagnosis [1].…”

“…All tumors enhance on MRI, and most of them have associated cysts with enhancing walls [1, 6, 21]. Some of them have hemorrhage or necrotic areas [1].…”