Posterior fossa neuroblastoma occurring in an elderly man.

A case of a neuroblastoma occurring in the cerebellum of a 73-year-old man is reported. The patient presented with progressive truncal ataxia and was found to have an enhancing tumor mass in the cerebellar vermis. By light microscopy, the tumor was a small cell neoplasm and was similar to medulloblastoma, with areas showing structures suggestive of Homer-Wright pseudorosettes. By electron microscopy and immunoperoxidase techniques, however, the tumor showed convincing evidence of neuronal differentiation. The absence of previous reports of this tumor in the posterior fossa of adults suggests that immunoperoxidase techniques and/or electron microscopy of such small cell tumors may be required for accurate diagnosis.