Solitary fibrous tumor of the female genital tract a case report and review of the literature.

Originally thought to be limited to mesothelial-lined surfaces, solitary fibrous tumor (SFT) has now been reported in numerous extrathoracic sites. The female genital tract is among the rarest reported sites involving SFT, and only a handful of cases have been described. Although features pointing to a more malignant biological behavior have been described, these tumors remain unpredictable in their clinical course. We present a case of primary SFT originating in the vulva of a 45-year-old woman, only the fourth such case and only the ninth case of primary SFT of the female genital tract. The tumor presented as a 60-mm, well-circumscribed, painless lump and comprised bland spindle cells in a collagenized stroma with hypercellular and hypocellular foci. Immunohistochemically, the spindle cells were strongly positive for CD34, Bcl 2, and vimentin, with focal positivity for CD99. Immunohistochemical staining for MNF116, desmin, smooth muscle actin, ER, PR, and S100 was negative. There has been no recurrence after 6 months. We discuss the principal differential diagnoses of spindle cell mesenchymal tumors of the vulva and review the previously published cases of primary SFTs originating in the female genital tract. We also stress the importance of informing clinicians involved in these cases of the potential for an unpredictable clinical outcome.