Cytomorphology of myxopapillary ependymoma

Abstract

Myxopapillary ependymoma (MPE) is a rare distinctive variant of ependymoma (EP) occurring predominantly in the conus‐cauda‐filum terminale region of adults. Cytologic features of MPE have rarely been described. Touch imprint smears of 11 cases of MPE (mean age: 43.5 year‐old, 8 males and 3 females) were reviewed and graded semi‐quantitatively for 10 different cytomorphologic parameters. Cytologic examination revealed low to moderately cellular specimens composed of scattered isolated and loosely aggregated tumor cells with round to oval or occasionally spindle‐shaped nuclei, fine evenly distributed chromatin, and a meshwork of delicate processes. Predominantly observed cytologic features included a myxoid background, isolated single tumor cells, and long delicate cytoplasmic processes reflecting the glial nature of this tumor. Approximately half of cases contained “hyaline globules” (HGs) of varying sizes. Papillary structure, a histological hallmark of MPE, was rarely observed. No intracytoplasmic lumina, intranuclear inclusions or mitotic figures were seen. On cytomorphologic grounds, MPE may resemble EP and chordoma. Relatively lower cellularity of exfoliated tumor cells and a distinctive myxoid background with occasional HGs, and the presence of prominent delicate cytoplasmic processes supports a diagnosis of MPE rather than EP and chordoma, respectively.