Cerebrospinal fluid cytology of an endolymphatic sac tumor

Endolymphatic sac tumor (ELST) is a rare neoplasm which is seldom evaluated by cytopathology. We report the clinicopathologic course and cytologic cerebrospinal fluid (CSF) findings in a 58-year-old patient with brainstem lesions who originally presented with vertigo but progressed to having left 7th, 8th, 9th, and 10th cranial nerve palsies, right-sided weakness, and occipital headaches. Cytospin of the CSF revealed large epithelioid cells similar to cells seen in a surgical resection of a brain mass three months previously. Review of the surgical specimen revealed a well-differentiated glandular and papillary neoplasm, most consistent with an endolymphatic sac tumor.