A case of hyalinizing spindle cell tumor with giant rosettes involving thepresacral area. Immunohistochemical and ultrastructural study

Hyalinizing spindle cell tumor with giant rosettes is a slowly growing tumo r with a risk of local recurrence in case of incomplete surgical excision t hat could be regarded as a distinctive type of low-grade fibroblastic tumor We report a case involving the presacral area. This tumor was composed of areas areas of bland spindle cell proliferation with a fascicular pattern i n a fibrous or myxoid stroma, intermixed with giant rosettes consisting of rounded cells surrounding a central collagen core. The tumor expressed vime ntin, and, for cells comprising the rosettes, S-100 protein, NSE and CD-57. These latter cells exhibited ultrastructural features of Schwann cells, th e tumoral cells of fascicular area exhibiting features of fibroblastic cell s. Flow cytometry showed DNA-aneuploidy and a very low S-phase fraction. Th is tumor appeared to be composed of two cellular components, fibroblastic a nd Schwann cells, located, at the opposite of neurofibroma, in two distinct areas.