Case report: diagnosis and surgical management of a rare malignant isolated fibrous tumor of the pelvis.

Solitary fibrous tumor (SFT) is an uncommon fibroblastic mesenchymal neoplasm. Malignant SFT in the abdominopelvic compartment，particularly originating from the anterior abdominal wall and peritoneum is exceptional. A 72-year-old woman presented with recurrent right lower-quadrant pain. Imaging demonstrated a ~13 cm heterogeneous, hypervascular mixed cystic solid pelvic mass supplied by the external iliac arteries and abutting the bowel and bladder. At operation, an encapsulated mass was found densely adherent to the peritoneum with rich peritumoral vascular connections; feeding vessels were individually clamped and secured, and the tumor was removed completely with en bloc excision of the adherent peritoneum. Pathology confirmed malignant SFT (necrosis and increased mitotic activity) with supportive immunophenotype (focal CD34/partial STAT6). The patient recovered uneventfully and remained recurrence-free on computed tomography at 12 months. This case highlights the value of vascular mapping for safe, complete resection.