Melanosomal melanin pigment in pleomorphic xanthoastrocytoma, evidence for neuronal‐glial origin: A case report with review of the literature

Abstract

We describe a unique case of pleomorphic xanthoastrocytoma (PXA) in a 19-year-old male presenting with the chief complaint of seizures. On radiology, the tumor was located in the temporal lobe. It was cortically based and solid cystic in nature. Light microscopy showed pleomorphic large polygonal cells with inclusions, nuclear clustering, lipidization, and foamy cytoplasm intermingled with spindle cells arranged in sweeping pattern and focally containing cytoplasmic brownish black pigment. The pigment stained black with Fontana-Masson stain and bleached with potassium permanganate. Gomori silver stain showed reticulin fibers surrounding individual tumor cells as well as groups of cells. On immunohistochemistry, tumor cells were positive for GFAP, S-100 and focally for synaptophysin and CD34 but negative for HMB-45. CD34 revealed a specific membranous pattern around individual cells as well as groups of cells along the fibers replicating a reticulin pattern. The ultrastructural examination showed supporting melanosomes, thus confirming the melanin pigment. Sequencing for BRAF V600E showed a heterozygous mutation. To our knowledge only five cases of PXA with melanin pigment have been reported and none of which described BRAF V600E mutation analysis. This case provides further insight into the origin and pathogenesis of pigmented astrocytic tumor, additionally highlighting the characteristic CD34 staining pattern.

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

“…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…”

“…To date, only nine cases have been reported in the English literature: one ganglioglioma, one pilocytic astrocytoma, and seven cases of pleomorphic xanthoastrocytoma (PXA). [1][2][3][4][5][6][7] Here we present an additional case of pigmented PXA along with its intraoperative cytologic findings, which have not been described before.…”

Melanocytic colonization of choroid plexus papilloma: A previously undocumented source of pigment storage in the plexogenic epithelium

“…On the other hand, a more generic -rather than mechanistic -argument of divergent differentiation/ lineage infidelity has been invoked to account for the presence of true melanosomes. Vague though it may be, this interpretation is nevertheless lent circumstantial evidential support per analogiam by the repeated occurrence of aberrant melanosomes in some non-neural crest-derived CNS tumors in particular gliomas as well [3,5,7]. For the sake of completeness, we further remark to have identified at least one case report on ependymoma -a close relative of choroid plexus tumors -containing both melanosomes and neuromelanin [4].…”

“…Conversely, aberrant pigment production by tumor cells as a seemingly erratic secondary phenomenon has been documented in several unrelated CNS neoplasms. The betterknown examples include pigmented variants of pilocytic astrocytoma [2], pleomorphic xanthoastrocytoma [3], ependymoma [4], ganglioglioma [5], dysembryoplastic neuroepithelial tumor [6], glioblastoma [7], medulloblastoma [8], and choroid plexus papilloma [9,10,11,12].…”

“…From case to case, the intracellular pigment may be either of melanosomal origin [3,5,7,8] or neuromelanin/lipofuscin [2,11], and has variously been interpreted as reflecting neoplastic transformation of pluripotent embryonal-like cells, lineage infidelity, or as a "wear-and-tear" phenomenon in prematurely senescent tumor cells.…”