A solitary fibrous tumour mimicking an aggressive angiomyxoma/liposarcoma

We present a case of a solitary fibrous tumour (SFT) resembling an aggressive angiomyxoma/liposarcoma on radiological imaging, causing significant diagnostic challenges preoperatively. A 76-year-old male was incidentally found to have a large pelvic mass on a CT scan. Further evaluation with an MRI scan confirmed a presacral mass containing fat and soft tissue components. It was inseparable from the sacrococcygeal spine, rectal serosa and the posterior wall of the urinary bladder, but no evidence of invasion was seen. A prominent vascular pedicle arising from the epidural vasculature was also noted. Differentials discussed at the multidisciplinary tumour board were an aggressive angiomyxoma versus a liposarcoma. The patient underwent wide resection of the pelvic tumour, anterior resection and end colostomy. Intraoperatively, a large 20 cm pelvic mass involving the sigmoid mesocolon and presacral fascia was found. Final histology reported an SFT with extensive adipocytic metaplasia.