Table of Contents
Washington University Experience | NEOPLASMS (EMBRYONAL) | Medulloblastoma, Histologically Defined | Medullomyoblastoma | 6H Case 6 Denouement
Not shown: GFAP reactivity is present mainly in the more differentiated areas. Neurofilament highlights a relatively solid growth pattern. Nuclear reactivity for INI-1 is retained. The tumor cells also show strong and diffuse cytoplasmic reactivity but no significant nuclear reactivity for beta-catenin. No reactivity for p53 is present. ---- FiSH reveals no evidence of MYCN or MYC gene amplification. ---- Histologically, this tumor has a classic medulloblastoma morphology with focal myogenic differentiation. Next-generation sequencing reveals three mutations: SMO (W535L) is indicative of SHH pathway activation; CTNNB1 is indicative of WNT pathway activation; and KDM6A mutation is seen in approximately 13% of group 4 (non-WNT/non-SHH) medulloblastomas. Thus, the histologic and genetic findings in this case are mixed. It has been reported that medulloblastomas with myogenic differentiation do not align well with genetically defined molecular subgroups. ---- Diagnosis: Medulloblastoma with myogenic differentiation, WNT-activated, SHH-activated, WHO grade IV (see
