[A clinico-pathological study of cystic spinal Schwannomas]

It is not rare for a spinal Schwannoma to have cystic formations, but there are various opinions about the mechanism. Since the installation of MRI in our institution in 1989, we have experienced 4 cases of cystic spinal Schwannoma. The diagnosis of such lesions was based on identifying cystic formations histopathologically. Among these cases, tiny hemorrhages were noted microscopically in three of them along with hemosiderin depositions and phagocytes containing hemosiderin. Besides, there are also a lot of sinusoidal vessels with thin endothelium. Perhaps in these three cases, it is the tiny hemorrhages that resulted in degenerative changes which in turn caused the formation of microcysts. But in addition to the above findings, a lot of hyalinized vessels were also demonstrated in the angiomatous components of two cases. Therefore, it is also possible that the microcyst formation is secondary to the degenerative changes caused by ischemia within the tumors. On the other hand, in the only case without hemorrhage, neither phagocytes containing hemosiderin nor abnormal sinusoidal vessels could be found. In stead, a lot of clear foamy cells with positive lipid staining were seen. There may be some factors underlying the xanthomatous change of these tumors that cause their vacuolar formation from degenerated of the foamy cells. It is possible that all three factors mentioned above may act alone or in combination to contribute to the formation of cysts. At its late stage, a spinal Schwannoma may have various findings which can not be classified into either Antoni A or Antoni B type. In conclusion, a spinal Schwannoma can occasionally have cystic formations. Its mechanisms can be a hemorrhagic or an ischemic process occurring within the tumor.