Lipomatous medulloblastoma in adults. A distinct clinicopathological entity.

We report on three patients who presented with a cerebellar medulloblastoma at age 48, 53, and 59 years. Histopathology showed typical features of medulloblastoma, in one case with marked neuronal differentiation. In addition, all neoplasms contained focal accumulations of mature fat cells. Immunoreactivity of adipocytes for S-100 protein, neuron-specific enolase, synaptophysin, microtubule-associated protein-2, and glial fibrillary acidic protein and the lack of immunoreactivity to type IV collagen suggest lipomatous differentiation of neoplastic primitive neuroectodermal cells rather than an admixture of mesenchymal elements. Mitotic activity was low and the growth faction, as determined by the MIB-1 labeling index, was less than 5%. All patients are alive with a recurrence-free interval ranging from 3.5 to 12 years. These three patients and five similar previously reported cases all fit into the concept of the lipomatous medulloblastoma as a new clinicopathological entity characterized by (a) typical features of a cerebellar medulloblastoma with advanced neuronal differentiation, (b) areas of lipomatous differentiation, (c) low proliferative potential, (d) manifestation in adults (mean age, 50 years), and (e) apparent favorable clinical prognosis.