Abstract
We report a case of solitary fibrous tumor (SFT) in the pelvic space. A 45-year-old woman who had been found to have a left ovarian tumor in a medical check-up underwent surgery. At laparotomy, a large smooth mass 7 cm in diameter was found in the left side of the pelvic space, and a needle biopsy was performed. Pathologically, the mass was diagnosed as a spindle cell tumor, suspected of being a low-grade malignant soft-tissue tumor. CT showed a large, round, heterogeneously enhanced, smooth-surfaced mass compressing the rectum and uterus. No invasion was detected. Colonoscopy showed that the lower rectum was compressed from the left side but that the mucosa appeared normal. Then the abdominosacral excision was performed. Macroscopic findings of the resected specimen showed an encapsulated yellowish-white elastic soft tumor sized 7.0×5.5×5.1 cm, colored. Histological examination demonstrated the tumor to be composed of cellular proliferation of spindle cells with a "patternless pattern" arrangement. Hypercellularity and pleomorphism were remarkable; however, mitosis was not seen. Immunohistochemical staining was positive for α-SMA, partially positive for vimentin and CD34, and negative for desmin, EMA, and S-100. These findings suggested a diagnosis of SFT in the pelvic space. The tumor had invaded the gluteus maximus muscle. The patient is alive without recurrence 7 years after the excision.
