Comments on the letters by Bruce Quinn and Douglas Miller:

Patel et al (1) described an unusually large number of spinal cord gangliogliomas. This finding prompted the letter by Dr. Quinn who challenged the accuracy of diagnosis because it appeared to him that these were largely based on the pattern of synaptophysin immunochemistry. Although Miller, as well as other pathologists, found the latter pattern of immunohistochemistry useful, Zhang and Rosenblum (2) and Quinn (3) have challenged the accuracy of synaptophysin staining for the diagnosis of ganglioglioma. Miller responds that synaptophysin immunohistochemistry was only used adjunctively or for confirmation. It is fair to conclude that reliance on synaptophysin immunohistochemistry alone for the diagnosis of ganglioglioma is not justified at this time. This issue is clearly controversial that we hope future studies will clarify. I, however, see little reason to doubt the diagnoses that have been rendered by two senior, highly experienced neuropathologists with extensive experience in neurooncology (Drs. Miller and Rorke). Miller and Rorke based their diagnoses largely on more traditional histologic evaluation, and immunochemical study for glial fibrillary acidic protein to distinguish ganglion cells from abnormal appearing astrocytes.