Solitary fibrous tumor of the upper respiratory tract. A report of six cases.

We report six cases of a neoplasm that arose in the upper respiratory tract and had a histological appearance indistinguishable from that of solitary fibrous tumor of the pleura (SFT, so-called fibrous mesothelioma). The patients were adults who presented with nasal obstruction. The lesions lacked the characteristic features of other recognized neoplasms that occur in this region. The tumor cells were immunoreactive for vimentin but not for keratin. The occurrence of SFT in this location further supports the argument that SFT is a tumor of mesenchymal and not mesothelial origin. None of the tumors in this series had the histologic features of malignancy described for SFT in other locations, and there was no aggressive behavior in limited follow-up. Until more cases of SFT in unusual locations have been studied, we recommend that the same criteria used for assessing aggressiveness in SFT of the pleura be applied to them.