Solitary fibrous tumour of the sacrum: A report of 2 cases with review of the literature

Introduction: Solitary fibrous tumour (SFT) of the sacrum is a very rare disease. So far, there have been few reports on this disease. Here, we reported 2 such cases and reviewed the other 7 reports in the literature. Case series: Case 1, a 48-year-old man presented with lumbosacral pain for 2 months and numbness in the left plantar region for more than 1 month. The report of CT scan indicated that the sacrum was destroyed and the soft tissue mass projected into the pelvis. Histopathology showed that the cells were fusiform or short fusiform, arranged in strips, sheets, and wavy patterns. Case 2, a 40-year-old woman presented with hip joint pain and lower extremity dyskinesia for more than 2 months. The result of the MRI examination demonstrated a mass on the right sacral foramen and anterior sacrum. The characteristics of histopathology are ovoid or spindle-shaped cells with focal nuclear pleomorphism and prominently branched, hemangiopericytoma-like vascular patterns. In addition, immunohistochemical showed that CD34, Bcl-2, CD99, STAT6 and vimentin were positive, while Desmin, MSA, EMA, S100 were negative in both cases. Conclusion: Previous literatures have revealed that SFTs of the sacrum are rare neoplasms. Case 1 and a part of these lesions previously reported seem to be malignant and should be treated with surgery. Radiation or chemotherapy was adopted if necessary. Since SFT of the sacrum is prone to recur and metastasis, long-term follow-up should be considered. To a certain extent, new risk stratification models can predict prognosis more accurately.