Septate-like junction of neoplastic cells in myxopapillary ependymoma of the human filum terminale

Abstract

Since the first description of septate desmosomes by Wood the term septate junction has been used to describe various junctional structures where in transverse section the intercellular space is partitioned by more or less regularly spaced septa. While septate junction is a common intercellular feature of invertebrate epithelium, vertebrates do not possess septate junctions. There have been occasional reports in the literature of septate-like structures in vertebrate tissues, mainly in nervous tissue and between epithelial cells.In an ultrastructural study of three cases of myxopapi1lary ependymoma of the fi1um terminale, structures similar to septate junction were observed in two cases. They were circumferential bands around the finger-like processes of neoplastic cells wherein slightly widened 30-40 nm intercel1ular spaces (as compared to 15-20 nm in non-junctional region) were transversed at regular intervals by parallel septa resulting in characteristic ladder-like appearance (Fig.1,2). The electron-dense septa, 30-40 nm in cross-length and 20-30 nm in width, were arranged in a periodicity of 40-50 nm. The septa connected to the outer leaflets of the apposing cytoplasmic membranes which appeared undisrupted. Most junctions were short the longest one contained 15 septa in a length of 1.4 um. Similar septa in the same intervals were also noted between the cytoplasmic membrane and the investing basement membrane(Fig.3). Junctional complexes such as zonula adherens and gap junction were often present in the vicinity(Fig.4). Septate-like junctions have not been described in previous studies of myxopapi11ary ependymoma nor in other human brain tumors. Similar junctions have not been observed in the normal conus medullaris nor fi1um terminale. They may represent a specific intercel 1ular feature of myxopapi11ary ependymoma.