Suprasellar monomorphous pilomyxoid neoplasm: an ultastructural analysis

The authors report 3 patients, 2 children and 1 adult. each of whom present ed with an unusual myxoid lesion reminiscent of pilocytic astrocytoma but w ith other features of myxopapillary ependymoma. The magnetic resonance imag ing findings in all cases showed a diffusely contrast-enhancing suprasellar mass focally extending into the third ventricle. Involvement of adjacent s tructures was more extensive in both infants. By light microscopy, all were composed of a monotonous population of cells with delicate piloid-like pro cesses, loosely arranged within a prominent myxoid background. Focally, the neoplastic cells converged upon small blood vessels in pseudorosette-like formations. These histomorphologic features are identical to those of the r ecently described astrocytoma with monomorphous pilomyxoid features. In add ition, the individual tumor cells showed strong cytoplasmic immunoreactivit y with antibodies to glial fibrillary acidic protein (GFAP) and vimentin, a s well as nuclear and cytoplasmic staining with S-100. All stained positive for synaptophysin and negative for chromogranin. By electron microscopy, t he tumor cells were bipolar with elongated processes and apical surfaces di splaying microvilli, cytoplasmic blebs and rare cilia. Vesicles and coated pits were seen, as were occasional synaptoid complexes. The current study s erves to expand our clinco-pathologic experience with this rare and enigmat ic lesion, with particular attention given to the ultrastructural character istics.