Solitary Fibrous Tumor of Retroperitoneum: An Unusual Localisation of an Uncommon Neoplasm

Abstract

Background: The solitary fibrous tumor (SFT) is a soft tissue tumor of fibroblastic origin. Most of the times, it develops in the thorax. Very infrequently, it appears in other locations such as the retroperitoneum or pelvis. Most cases have benign behavior, characterized by a slow localized growth, but 10-20% of cases are locally aggressive or metastasize in distant locations. Case Report: We present a case of extra-pleural SFT, in an unusual location, at the mesorectum. It reached 8 cm maximal diameter, and was accompanied by macroscopic traits of local malignancy. Histopathological examination and immunohistochemistry revealed a mesenchymal fusocellular/spindle cell tumor. Conclusion: Although an uncommon mesenchymal neoplasia, SFT should be kept in mind when making the differential diagnosis of pelvic masses. It should be considered as a neoplasm with a high risk of local recurrence or metastasis.