A Rare Case of Solitary Fibrous Tumor Originating in the Peritoneum: Clinical and Histopathological Insights.

Solitary fibrous tumors (SFTs) are rare mesenchymal neoplasms that most commonly arise from the pleura, with peritoneal origin being exceptionally uncommon. We report a case of a 51-year-old male who presented with a large abdominal mass, subsequently diagnosed as a solitary fibrous tumor originating from the peritoneum. Radiological evaluation revealed a well-defined mass with a vascular pedicle supplied by the inferior mesenteric artery, extending from the pelvis to the lower abdomen. Surgical resection of the tumor, including part of the rectosigmoid junction was performed and histopathology confirmed the diagnosis of SFT. Immunohistochemistry (IHC) demonstrated positive staining for CD34, BCL2, and STAT6, supporting the diagnosis. The patient remains disease-free after four years of follow-up. This case contributes to the limited literature on peritoneal SFTs, highlighting the importance of IHC in clinching the diagnosis and of long-term follow-up due to the potential for late recurrence.