Complete Resection of a Giant Hypervascular Pelvic Floor Solitary Fibrous Tumor Using Intraoperative Balloon Occlusion and Staged Open Abdomen Management: A Case Report

INTRODUCTION: Solitary fibrous tumors (SFTs) are rare fibroblastic neoplasms that can occur at various anatomical sites, including the pleura, retroperitoneum, and pelvis. Although surgical resection remains the mainstay of curative treatment, pelvic SFTs often present as giant hypervascular tumors, making intraoperative bleeding control particularly challenging. CASE PRESENTATION: A 66-year-old man presented with progressive abdominal distension, constipation, and dysuria. CT revealed a large pelvic mass measuring 200 × 176 × 140 mm, with multiple intratumoral vessels and areas of necrosis accompanied by bilateral hydronephrosis. MRI revealed a heterogeneously hyperintense signal on T2-weighted images. Preoperative angiography revealed multiple feeding arteries from the bilateral internal iliac, inferior mesenteric, and median sacral arteries. Preoperative embolization was deemed technically difficult because of the extensive vascular network. Intraoperative balloon occlusion catheters were therefore placed in both internal iliac arteries to control pelvic blood flow. The tumor was resected via open surgery, along with partial cystectomy and ureteral resection, followed by reconstruction. Persistent venous oozing required temporary open abdomen management using Abthera, and definitive closure was achieved the following day after confirmation of hemostasis and application of Surgiflo. The resected specimen measured 210 × 200 × 140 mm and weighed 2865 g. Histologically, the tumor consisted of spindle cells with low mitotic activity. Immunohistochemistry revealed positivity for signal transducer and activator of transcription 6 (STAT6) and negativity for cluster of differentiation 34 (CD34), confirming the diagnosis of SFT. The postoperative course was complicated by pulmonary embolism, which was successfully managed with anticoagulation therapy. The patient remains disease-free 1 month after surgery. CONCLUSIONS: This case of a giant pelvic floor SFT with CD34 negativity and STAT6 positivity demonstrates that intraoperative balloon occlusion and staged open abdominal management can be effective strategies for controlling intraoperative bleeding in hypervascular pelvic tumors. Individualized planning and staged approaches are crucial for facilitating tumor resection in such highly challenging cases.