Background: Myxopapillary ependymoma is a variant of ependymoma that usually occurs in the sacrococcygeal region. Histologically, it is characterized by arborizing papillary fronds of capillaries with mucinous stroma rimmed by ependymal cells. The fine needle aspiration cytology of this rare tumor is rarely described in the literature.
Case: We report the fine needle aspiration cytology of a primary sacrococcygeal myxopapillary ependymoma occurring in a 18-year-old female. Cytology showed "fernlike" papillae and globules of mucinous and myxoid substance containing central capillaries. These structures were rimmed by one to several layers of mitotically inactive, mildly pleomorphic cuboidal to columnar cells with occasional pseudonuclear cytoplasmic inclusions. Some of these ependymal cells sent fibrillary processes toward the capillaries, suggestive of perivascular pseudorosettes. There were also numerous isolated tumor cells in the background.
Conclusion: Because of the prominent mucinous elements and papillary fronds, myxopapillary ependymoma may mimic other myxoid or papillary tumors cytologically. Recognition of the characteristic cytologic features may allow a distinction to be made on fine needle aspiration biopsy.