Perivascular pseudorosettes (ependymoma)

Perivascular pseudorosettes are a common histologic feature of central nervous system ependymomas. They represent sections through papillary structures composed of tumor cells arranged radially around a central vessel. Between the central vessel and the tumor cells is a relatively microscopically clear region filled with cytoplasmic processes that are strongly positive for GFAP . In myxopapillary ependymomas, myxoid material will also be present within this clear space, sometimes forming microcysts .

Perivascular pseudorosettes should not be confused for features of ependymomas:

• ependymal rosette
• EMA positive perinuclear dot sometimes forming intracytoplasmic microrosettes