Primary rhabdomyosarcoma of the central nervous system.

A case of primary rhabdomyosarcoma in the brain stem is described in an 8 year old girl. The clinical data showed a right side hemiplegia then a total paralysis of the left sixth cranial nerve and a paraplegia which became lethal in 3 months. The necrospy revealed a tumoral nodule in the left medulla oblongata and pons with diffuse subarachnoidal extension from the cranial nerves to the cauda equine roots. Histologically the tumor appeared to be polymorph with numerous rhabdomyoblasts which had a clear cross striation and which were sometimes less differentiated without any neuronal or glial elements. Perivascular tumoral cells and blood vessels were closely linked, the Virchow-Robin spaces were clearly involved. The electron microscopic study confirmed that the less differentiated cells were of a rhabdomyoblastic nature. A review of the litterature indicates that these malignant neoplasias are highly exceptional, and can be classified within the group of primary tumors of the neuraxis with muscular elements. The histogenetic origin of these tumors appears to be the ectomesenchyme of neural crests.