Recurrent malignant solitary fibrous tumor of pelvis: A case report and treatment approach

Solitary fibrous tumors (SFTs) are rare mesenchymal neoplasms that typically arise from the pleura but can also occur in various locations throughout the body. Although there are increasingly more reports of extra-pleural SFTs, reports of SFTs in bone are very rare, and a malignant SFT accompanying recurrence of pelvis has not yet been reported. PATIENT CONCERNS: We herein present the case of a 15-year-old male who experienced intermittent numbness in his right buttock, accompanied by radiating pain in his lower limbs for 6 months. Radiological examinations revealed an expansive, heterogeneous enhanced mass in the sacral and iliac regions, with a branch of the right internal iliac artery feeding the tumor. DIAGNOSES: The histological examination suggest a diagnosis of a malignant SFT with high proliferation activity. INTERVENTIONS: The sacral mass was surgically excised. OUTCOMES: Following the surgery, the patient experienced a local recurrence of the tumor at 9 months and was administered adjuvant imatinib treatment. Recent magnetic resonance imaging contrast-enhanced displayed shrinkage of the tumor, which may provide certain evidence for chemotherapy for the treatment of recurrence of malignant SFTs in the pelvic region. LESSONS: Complete surgical excision is the recommended treatment for this rare disease entity, and the role of adjuvant therapies is controversial due to their rarity. Our case underscores the challenges in managing recurrent malignant SFTs and highlights the importance of a thorough diagnostic workup. Further research is needed to establish the role of adjuvant therapies in the management of these tumors.