Pigmented Ependymoma of the Fourth Ventricle—A Curious Entity: Report of a Rare Case With Review of Literature

Abstract

A 16-year-old boy presented with a tumor located in fourth ventricle, which showed histological features of an ependymoma replete with perivascular pseudorosettes and true ependymal rosettes. Interestingly, many of the tumor cells exhibited abundant cytoplasm stuffed with a grayish brown pigment. Histochemical stains showed the pigment to be acid fast and periodic acid–Schiff positive and negative for Masson-Fontana melanin stain. Additionally, the pigment displayed brilliant autofluorescence under ultraviolet light of a fluorescent microscope. Ultrastructure examination of the pigment revealed a non–membrane-bound biphasic structure with an electron-dense core and electron-lucent periphery. Only few similar case reports mention such pigmented ependymomas to contain a mixture of neuromelanin and lipofuscin while others mention it to be melanin itself. Our workup suggests the pigment to represent lipofuscin or its derivative. Generally known to be a pigment of wear and tear, the significance of finding it in a tumor with such abundance remains to be understood and explored.

Cytologic and histologic features of pigmented pleomorphic xanthoastrocytoma: A case report and literature review

“…Neuromelanin is found in the neurons of the substantia nigrae and the loci ceruleus among other structures such as the dorsal motor vagal nuclei; it stains positive with PAS and Fontana Masson 1,9 . Lipofuscin is both PAS and acid‐fast positive 9,10 . All the reported rare pigmented PXAs contained melanosomal melanin.…”

“…Melanosomal melanin, found in the choroid of the eye and in the meninges, is produced in melanosomes. 9 It typically stains black with Fontana Masson, bleaches with potassium permanganate, and is in melanosomes in ultrastructure examination. 1 Although the mechanism requires further investigation, the fact that both cells of melanocytic lineage and glial-neural lineage derive from truncal neural crest cells…”

“…Three types of pigments are documented in the central nervous system: melanosomal melanin, neuromelanin, and lipofuscin. Melanosomal melanin, found in the choroid of the eye and in the meninges, is produced in melanosomes 9 . It typically stains black with Fontana Masson, bleaches with potassium permanganate, and is in melanosomes in ultrastructure examination 1 .…”

“…Neuromelanin and lipofuscin, on the other hand, are histochemically related and both accumulate in aging brains. Neuromelanin is found in the neurons of the substantia nigrae and the loci ceruleus among other structures such as the dorsal motor vagal nuclei; it stains positive with PAS and Fontana Masson 1,9 . Lipofuscin is both PAS and acid‐fast positive 9,10 .…”

“…1,9 Lipofuscin is both PAS and acid-fast positive. 9,10 All the reported rare pigmented PXAs contained melanosomal melanin. both of which were characteristic of PXA but not consistently present in every case.…”