Myxoid solitary fibrous tumour: instructive case and literature review

Myxoid solitary fibrous tumour (SFT) is a rare soft tissue neoplasm, which was initially described by de Saint Aubain Somerhausen et al in 1999. Myxoid SFT is an SFT with myxoid change in 50% or more of the tumour. We report the case of a 50-year-old man with a myxoid SFT found in the right pelvis. Microscopically, the lesion was composed of spindle cells arranged in a haphazard and storiform pattern, individually separated by delicate band of collagen fibres, in a cellular and hypocellular myxoid background with hemangiopericytomatous vessels. Atypical features (necrosis, hypercellularity or increased mitotic figures) were absent. Immunohistochemistry demonstrated tumour cells that were highlighted by CD34, CD99, and BCL2. The lesion was resected and to date, there is no evidence of tumour recurrence or metastasis. Myxoid SFT like classical SFT may be associated with an indolent clinical course and favourable prognosis. Its recognition is crucial because of its morphological similarities to myxoid spindle cell neoplasms that have different prognoses and treatment options.