Malignant phosphaturic mesenchymal tumor with pulmonary metastasis

RATIONALE Phosphaturic mesenchymal tumor (PMT) is a new tumor entity of soft tissue and bone tumor recently accepted by the World Health Organization, which typically causes the paraneoplastic syndrome of tumor-induced osteomalacia (TIO). The majority of PMTs follow a benign clinical course and local recurrence occurs in < 10% of cases, malignant PMTs with distant organ metastasis are extremely uncommon. PATIENT CONCERNS We reported a 41-year-old woman who was diagnosed with PMT 10 years ago with a repeated recurrence and pulmonary metastasis. DIAGNOSES Based on clinical manifestations, MRI scan, serum biochemical indicators evaluation, followed by histopathological examination, the patient was diagnosed as malignant PMT with pulmonary metastasis. INTERVENTIONS The patient was treated with calcium, phosphorus, and vitamin D after surgical resection and measured the serum ion concentrations every 3 months. OUTCOMES The patient had a favorable outcome for 10 months without recurrence. LESSONS PMTs lack of characteristic histological morphology, some recurrence cases may appear benign morphologically; the malignant PMTs are easily overlooked. Patients with PMT should be carefully evaluated and monitored, in order to early identify its malignant potential.