Malignant phosphaturic mesenchymal tumors (MPMT) are rarely seen soft tissue tumors. They can result in tumor-induced osteomalacia with hypophosphatemia. These tumors show FN1::FGFR1/FGF1 gene fusions Show more
Malignant phosphaturic mesenchymal tumors (MPMT) are rarely seen soft tissue tumors. They can result in tumor-induced osteomalacia with hypophosphatemia. These tumors show FN1::FGFR1/FGF1 gene fusions. We present a 59-year-old male patient with a swelling in his right knee. Magnetic resonance imaging examination revealed a soft tissue mass with a maximum diameter of 2 cm in his distal right thigh. Histopathologically, the tumor was composed of atypical spindle cells. Coagulative tumor cell necrosis, extensive osteoid-like matrix, calcifications, and aneurysmal bone cyst-like areas were present. Mitotic index was 16/mm Show less