Soft tissue, phosphaturic mesenchymal tumour [LMP17819]

49-year-old woman with osteomalacia, hypophosphatemia, and history multiple fractures. Clinically, she was suspected to have oncogenic osteomalacia and an octreotide scan revealed avid uptake at the level of the right frontal lobe. Further neuroimaging confirmed a large dural-based mass.

Clinical Discussion

Phosphaturic mesenchymal tumours are extremely rare neoplasms of uncertain differentiation that may cause oncogenic osteomalacia through production of fibroblast growth factor 23. An intracranial location is exceptionally rare. The tumour is usually composed of stellate/spindled cells that produce a smudgy, hyalinized matrix which can calcify. Osteoclasts, fibrohistiocytic spindled cells, hemorrhage, mature adipose tissue, and microcystic change may be seen. The majority of these tumours follow a benign course.