Medullomyoblastoma: a radiographic and clinicopathologic analysis of six cases and review of the literature.

Medullomyoblastoma (MMB) is a rare cerebellar embryonal neoplasm that occurs almost exclusively in children. It is biphasic by microscopy, containing myoblastic and primitive neuroectodermal components. The authors conducted a retrospective review of the radiographic and pathologic characteristics, treatment, and clinical outcomes of six children with MMB who were treated at St. Jude Children's Research Hospital (Memphis, TN) between 1984 and 2003. Fluorescence in situ hybridization (FISH) data were available for four children. A literature review also was conducted and focused on imaging and pathologic findings. The median age at diagnosis was 4.5 years (range, 0.83-7.5 years). Radiographically, all tumors were cerebellar and exhibited variable enhancement, and 50% of tumors had necrotic foci. Three tumors contained discrete, magnetic resonance imaging (MRI) T2-weighted-hypointense/computed tomography (CT)-hyperdense enhancing regions and separate hyperintense/hypodense nonenhancing regions, which correlated microscopically with geographic islands of primitive neuroectodermal and rhabdomyoblastic cells. Large cell/anaplastic (five tumors), nodular/desmoplastic (two tumors), and classic (two tumors) medulloblastoma histologies were encountered either alone (five tumors) or in combination with each other (two tumors). All 4 tumors that were tested exhibited alterations in chromosome 17 or c-myc amplification. All patients underwent macroscopic total resection and subsequently received chemotherapy and craniospinal (five patients) or local conformal (one patient) radiotherapy. At a median follow-up of 92 months (range, 23-187 months), 3 patients remain alive with no evidence of disease, 2 patients have died of disease, and 1 patient has died of secondary acute lymphocytic leukemia. The results of the current study demonstrated the frequent correlation of biphasic nodularity (as determined by MRI or CT) with discrete rhabdomyoblastic and primitive neuroectodermal islands (as revealed by microscopy) in MMB. These results also support the view that MMB and medulloblastoma may have common tumorigenic origins, given their similar histologic and molecular features.