Malignant phosphaturic mesenchymal tumor-ossifying fibroma-like subtype: a case report and literature review

Background A phosphaturic mesenchymal tumor (PMT) is classified into four histological subtypes: mixed connective tissue, osteoblast-like, non-ossifying fibroma-like, and ossifying fibroma-like. The ossifying fibroma-like subtype being extremely rare. Most PMTs are benign, with a minimal number becoming malignant after recurrence. In this study, we report a case of recurrence and malignant transformation of PMT-ossifying fibroma-like subtype in the left hip bone. Case presentation Here, we report the clinical manifestations, histology, pathological features, and treatment of a 57-year-old Chinese woman with a recurrent and malignant ossifying fibroma-like subtype PMT of the left iliac bone. The tumor was first discovered 3 years ago when the patient underwent surgery to remove the tumor. Precisely 2 years and 6 months after the operation, the pain in the left hip reappeared. After 6 months, the patient went to our hospital for treatment. After the tumor resection, the postoperative symptoms improved significantly, and the serum alkaline phosphatase level returned to normal. Based on clinical manifestations, evaluation of serum biochemical indicators, X-ray examination, computerized tomography scan of the pelvis, and histopathological examination of the two operations, the patient was finally diagnosed with a recurring and malignant transformation of the left iliac bone phosphaturic mesenchymal tumor-ossifying fibroma-like subtype. No tumor recurrence was found during the follow-up 15 months after the operation. Conclusions This case increases the awareness of a rare malignant subtype of PMT and provides a valuable reference for the diagnosis of this disease.

Sternal Phosphaturic Mesenchymal Tumor-Induced Osteomalacia, Diagnosis and Management: A Case Report

Background: Tumor induced osteomalacia (TIO) is a rare paraneoplastic disorder in which overproduction of fibroblast growth factor-23 (FGF-23) by mesenchymal tumor results in decreased renal phosphorus reabsorption and low to inappropriately normal 1,25-dihydroxyvitamin D, leading to hypophosphatemia and osteomalacia. Patients often present with bone pain, fractures, muscle weakness, and progressive decline in mobility. Due to the nonspecific nature of presenting symptoms of TIO diagnosis is often delayed. Clinical Case: A 55-year-old male presented with complaints of chest pain, shortness of breath, and generalized weakness following a ground level fall. Patient also reported a 10-year history of osteoarthritis with chronic back pain and 1-year history of generalized weakness, resulting in significant decline in functional status. On work-up, the initial CT scan of chest revealed multiple fractures including ribs, manubrium, scapula, and pubic rami. Subsequent biochemical evaluation was remarkable for hypophosphatemia to low of 1.3 mg/dL (2.4 - 5.0 mg/dL), low of 1,25-dihydroxyvitamin D of 13.1 pg/ml (19.9 - 79.3 pg/mL), reduced tubular phosphate reabsorption rate of 28% (normal > 80%) ratifying for renal phosphate wasting, normal iPTH level, and elevated serum FGF-23 level of 460 (normal < 180). Then, localization imaging for TIO was performed. After PET/CT scan showing increased uptake at the sternal area suggestive of lytic metastasis, subsequent CT angiogram of the chest identified mottled, irregular, mildly expansile appearance of the sternal manubrium. Sternal biopsy revealed phosphaturic mesenchymal tumor with positive FGF 23 mRNA expression. Surgical resection was delayed due to poor functional status and concurrent discovery of an EBV-positive nasopharyngeal carcinoma. Prior to surgery patient was treated with phosphorus and calcitriol supplements. Post-operatively serum phosphorus and FGF-23 levels were normalized. Patient also improved clinically. Patients treatment course was complicated by secondary hyperparathyroidism; however, this improved following surgery. Conclusion: Diagnosis of TIO can be delayed due to its nonspecific symptoms. Thus, in patients with chronic bone pain, muscle weakness, and atraumatic fractures, TIO should be kept on the differential and these patients should undergo thorough biochemical and imaging evaluation. Tumor localization could be challenging. Patients should be managed with supplements of active vitamin D and phosphorus with goal to normalize phosphorus level to prevent further bone demineralization prior to surgery. However, surgical intervention remains the mainstay of management as this is curative of TIO.