RESUMEN
A primary hemangiopericytoma (HP) of the bone is rare, because the vast majority of these tumors arise in soft tissue. This report presents a case of a hemangiopericytoma in the sacrum (S1-S2) with extension to the retrorectal space. Only a few cases of osseous hemangiopericytomas in the sacrum and involving the retrorectal space have so far been reported. The difficult diagnosis of HP and the surgical strategy was chosen according to the location of the lesion in the sacrum and retrorectal space. A local excision was indicated. A sacral resection should be considered for tumors below S4. This report demonstrated the safety of this strategy. Adjuvant radiotherapy is useful in HP. The value of chemotherapy is still doubtful, although patients with high-grade tumors or metastatic spread seem to gain substantial benefit. Due to the often unpredictable behavior of this neoplasm, extended follow-up is strongly recommended.