Primary omental malignant solitary fibrous tumour, an extremely rare malignancy: A case report and review of the literature.

Primary omental malignant solitary fibrous tumour is an extremely rare neoplasm considering its tumour origin and pathologic characteristics. Solitary fibrous tumour (SFT) is a spindle cell neoplasm that was first described in 1931. SFT is diagnosed at immunohistochemical stain including CD34, bcl2, CD99 and STAT6. Though most of SFTs are benign in nature, 5-15% are malignant. The diagnostic criteria of malignant SFTs are high cellularity, high mitotic activity(>4/10HPF), pleomorphism, necrosis and haemorrhage. We present the case of a 57-year-old male patient diagnosed with primary omental malignant SFT. Neither tumour origin nor pathologic diagnosis were possible based on preoperative information. Nevertheless, tumour resection was performed successfully. Several SFT cases involving omentum without malignant potential have been reported. However, primary omental malignant SFTs are extremely rare with only 3 cases reported in the literature.