Syringomyelia secondary to compression of the cervical spinal cord by an extramedullary lymphoma. A case of syringomyelia secondary to an extramedullary cervical spinal cord compression by a non-Hodgkin's lymphoma is described. After radiotherapy, the syrinx was no longer seen. The pathogenesis of this type of syrinx is discussed, and the potential benefit of radiotherapy in these cases is suggested. 