Table of Contents
Washington University Experience | NEOPLASMS (EMBRYONAL) | Medulloblastoma, Histologically Defined | Extensive Nodularity (MBEN) | 1B1 Medulloblastoma, nodular (Case 1) 1 H&E 1
1B1-3 This is a biphasic neoplasm. One phase is composed of a streaming network of intensely eosinophilic, moderately collagenous, richly vascularized, hypercellular tumor tissue (stromal phase). Embedded within this desmoplastic tissue is the second phase, composed of irregular islands of pale eosinophilic variably hypo- and hypercellular tumor tissue, often with a hypocellular rim (nodular phase). The cells within the pale islands are generally homogeneous, with round nuclei, darkly speckled chromatin, a small basophilic nucleolus, and poor cellular demarcation, with cytoplasm forming a fine, fibrillary background. The cells within the streaming stromal phase generally have elongate, oval nuclei, usually separated by thin strands of collagen, but focally appear more primitive, with mildly irregular nuclear contours, and dense chromatin. Mitotic figures range up to seven per ten high power (40X objective) fields, and are much more abundant in the desmoplastic stromal phase. Scattered apoptotic cells are identified, but these are not abundant. Other features of anaplasia (e.g.; large nuclei with aberrant contours, prominent nucleoli, 'cell wrapping') are rare to absent.
