A rare case of solitary fibrous tumour of the pre-sacral space: morphological and immunohistochemical features.

A 28-year-old woman presented with abdominal pain. Ultrasonograhic examination showed a pre-sacral mass, with complex structure and well delimitated cystss with thick walls. The resected specimen was 7.5 x 6 x 4 cm in size, well circumscribed and yellow in colour, with cysstic change containing mucoid-like material. Histologically, the lesion was composed of spindle cells with high cellularity and rich vascularization with a haemangiopericytoma-like pattern. The diagnosis of solitary fibrous tumour (SFT) was made. The differential diagnosis for SFT of the pre-sacral spaace involves haemangiopericytoma, GIST, malignant mesothelioma, synovial sarcoma, leiomyomatous tumours and granulosa cell tumour. Immunohistochemical studies revealed reactivity for CD34, CD99 and Bcl-2, but no staining for desmin, inhibin, c-kit, EMA, CK, SMA, S-100 and CD31, confirming a diagnosis of SFT. Although SFT is usually associated with a favourable prognosis, close follow-up is recommended because of the limited information on its long-term behaviour.