• BONE TUMOURS
• BONE TUMOUR PATHOLOGY
• IMMUNOHISTOCHEMISTRY

Phosphaturic mesenchymal tumour (PMT) is a rare mesenchymal tumour, which most often occurs in middle-aged adults, either in soft tissue or bone.1 ,2 PMTs are variable in their histomorphological appearance but often show a mixture of bland spindle cells embedded in a highly vascular (hemangiopericytoma-like) myxochondroid matrix, mature fat and osteoclast-like giant cells (figure 1A, B). The differential diagnosis of PMT is broad. In most cases of PMT, the patient has a longstanding clinical history of osteomalacia, facilitating the diagnosis of PMT. However, unsuspected PMT may be histomorphologically confused with other giant cell containing bone tumours, including chondromyxoid fibromas and chondroblastomas. Recognition of the distinctive ‘grungy’-appearing calcified matrix is the best way to distinguish PMT from other tumours (figure 1B). Detection of Fibroblast Growth Factor (FGF23) expression is …