PMC5329680_01
Magnetic resonance imaging scans/histopathological findings (anaplastic component). (a) Postcontrast T1 (right), T2-weighted (center), and fluid attenuated inversion recovery, FLAIR, sequence (left) in axial and coronal planes demonstrating a left periventricular, partially cystic, and bulky tumour. (b) Panoramical low magnification photomicrograph showing a densely populated neoplasm apparently assembling rosettes (right upper field) and surrounded by geographic necrosis (left lower field). (c) High magnification photomicrograph of the right upper field shown in (b). There are multiple perivascular pseudorosettes denoting conspicuous microvascular proliferation. (d) Mitotic activity in a high-power field. (e) Ki-67 immunolabeling index (~50%).
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Magnetic resonance imaging (MRI) scans revealed a left intra- and paraventricular frontal tumour with cystic parts and manifestly enhancing edges after contrast medium administration (Figure 1(a)). Histopathological examination of it disclosed a densely populated neuroepithelial neoplasm formed by sheets of small, mitotically active, hyperchromatic glial cells lumping around vessels exhibiting microvascular proliferation (Figures 1(b)-1(e)).
Histopathological findings (lipomatous/vacuolated component). (a) Low magnification photomicrograph showing numerous dystrophic calcification foci (left field) around areas resembling fat lobules (right upper field). (b) Signet-ring cells with an optically empty cytoplasm resembling adipose tissue. (c) Heavily hyalinised vessel with dystrophic calcification in a high-power field. (d) Densely collagenised vessel seen with Masson's trichrome in a high-power field. (e) Fortuitously found ependymal channel (blue arrows). This one attests partial vacuolation of the ependymal lining. (f) Boundary zone between a signet-ring cell area (green arrowhead) and the anaplastic component (right field). The black asterisks plot a long tailed blood vessel which ends in a microvascular proliferated glomerulus-like head.
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Nevertheless, to our surprise, there were also some other regions displaying an entirely different morphology, and which composed approximately 50% of the sample, featuring cells with a large optically clear vacuole pushing the nucleus to the periphery resembling either mature adipose tissue or signet-ring cells (Figures 2(a) and 2(b)). Blood vessels in these areas did not show microvascular proliferation but instead were hyalinised and calcified (Figures 2(c) and 2(d)). The ependymal nature of these curious neoplastic cells was also not evident; however, we incidentally came across some canalicular formations lined by ciliated cylindrical cells exhibiting the same vacuolative changes as the signet-ring-like ones (Figure 2(e)). Furthermore, there were transition zones between the lipomatous/vacuolated and the anaplastic component (Figure 2(f)).
Immunohistochemistry panel/transmission electron microscopy. (a) Glial fibrillary acidic protein (GFAP). (b) CD99. (c) PS100. (d) Ki-67 (MIB-1). (e, f) Uni- and multivacuolated cells featuring void lumina. (g) Rough endoplasmic reticulum (blue arrowhead) near an empty vacuole (orange asterisk). There is no apparent connection between them. On the left side, a small part of the cell's nucleus can be seen (green asterisk). (h) Hollow intracytoplasmic lumen containing granulofibrillary debris, slightly resembling degenerated microvilli or organelles, next to the nucleus (right field). (i) Microrosette filled with microvilli (green arrowhead) lying close to a dilated vacuole with granulofibrillary material (blue asterisk).
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PS100 (Figures 3(a)-3(c)) while no reaction towards epithelial membrane antigen (EMA) was observed. Conversely to the anaplastic part of the neoplasm, the Ki-67 proliferation index was extremely low here (<1%) (Figure 3(d)). Paraffin-embedded tissue was retrieved for transmission electron microscopy which, again, failed to recognise any particular substance inside the vacuoles, as just void gaps were persistently observed (Figures 3(e) and 3(f)). No relationship with endoplasmic reticulum or other organelles could be identified (Figure 3(g)). Intriguingly, granulofibrillary material was eventually found attached to the vacuoles' circumference barely resembling some kind of degenerated component (Figures 3(h) and 3(i)). Small intracytoplasmic lumina filled with multiple microvilli (microrosettes) were also recognised, confirming ultrastructurally the ependymal nature of the vacuolated cells (Figure 3(i)).