Phosphaturic mesenchymal tumors: A pathological perspective

Phosphaturic mesenchymal tumors (PMTs) are a rare group of neoplasms most commonly associated with tumor-induced osteocalcin (TIO), a paraneoplastic syndrome that profoundly impairs quality of life. Because the clinical manifestations are nonspecific, diagnosis is often delayed. PMTs are characterized by recurrent molecular alterations, most notably FN1::FGFR1 and KL (Klotho/α-Klotho) rearrangements. Tumor cells secrete fibroblast growth factor 23 (FGF23), which disrupts phosphate homeostasis and results in hypophosphatemia, thereby causing bone pain, fragility fractures, and skeletal deformities. Advanced imaging techniques play a central role in localizing the tumor, while complete surgical resection remains the most effective curative approach. Pathological evaluation provides the diagnostic gold standard; however, both clinical and histological features are heterogeneous, and the criteria for malignancy are not yet well defined. Furthermore, the biological significance of tumor margins remains an open question. This review summarizes the clinical presentation, molecular pathogenesis, pathological features, diagnostic strategies, therapeutic options, and prognostic implications of PMTs, highlighting current challenges and areas for future investigation.