Phosphaturic Mesenchymal Tumor

Phosphaturic mesenchymal tumor: management and outcomes of ten patients treated at a single institution

BACKGROUND

Phosphaturic mesenchymal tumor (PMT) is a rare tumor that causes tumor-induced osteomalacia. Patients present with non-specific symptoms secondary to renal phosphate wasting and decreased bone mineralization. We sought to assess: (1) What are the common presenting features, laboratory and imaging findings, histologic findings of phosphaturic mesenchymal tumors? (2) What are the available treatment strategies for phosphaturic mesenchymal tumors and their long-term outcomes in terms of local recurrence and symptom control after treatment?

METHODS

We retrospectively identified patients with a histologic diagnosis of PMT located in the axial or appendicular skeleton, or surrounding soft tissues. A total of 10 patients were finally included in our study.

RESULTS

Median tumor size was 1.9 cm (range, 1.1 to 6.1) and median time from symptom onset to diagnosis was 3 years (range, 0.5 to 15 years). All patients but one presented with hypophosphatemia (median 1.9 mg/dL, range 1.2 to 3.2). Pre-operative FGF-23 was elevated in all cases (median 423.5 RU/mL, range 235 to 8950). Six patients underwent surgical resection, three were treated percutaneously (radiofrequency ablation or cryoablation), and one refused treatment. Only one patient developed local recurrence and no patients developed metastatic disease. At last follow-up, nine patients showed no evidence of disease and one was alive with disease.

CONCLUSION

Phosphaturic mesenchymal tumor is a rare tumor presenting with non-specific symptoms. Surgery is the standard treatment when negative margins can be achieved without significant morbidity. In patients with small tumors in surgically-inaccessible areas, radiofrequency ablation or cryoablation can be performed successfully.

Intracranial Phosphaturic Mesenchymal Tumor Detected by 68 Ga-DOTATATE PET/CT

ABSTRACT

A 68 Ga-DOTATATE PET/CT scan was conducted to locate the causative tumor responsible for suspected tumor-induced osteomalacia in a 56-year-old woman. The PET/CT images showed a focus in the right occipital region. Subsequent MRI showed an extra-axial nodule in the right occipital region, mimicking a meningioma. Although rare, an intracranial phosphaturic mesenchymal tumor was still suspected because of the typical clinical settings. Finally, phosphaturic mesenchymal tumor was confirmed by the postoperative pathology.

Phosphaturic mesenchymal tumor: two cases highlighting differences in clinical and radiologic presentation

Phosphaturic mesenchymal tumors are rare, usually benign neoplasms that occur in the soft tissue or bone and are the cause of nearly all cases of tumor-induced osteomalacia. Tumor-induced osteomalacia due to phosphaturic mesenchymal tumor is a challenging diagnosis to make-patients present with variable clinical and radiologic findings and the culprit neoplasm is often small and can occur anywhere head to toe. We present two cases of phosphaturic mesenchymal tumor in the scapular body and plantar foot. In both cases, the patient endured years of debilitating symptoms before a tissue diagnosis was eventually reached. Descriptions of clinical presentation, laboratory workup, surgical resection, and imaging characteristics, with a focus on CT, MRI, and functional imaging, are provided to assist with the diagnosis and management of this rare entity. A brief review of current literature and discussion of the differential diagnoses of phosphaturic mesenchymal tumor is also provided.

Tumor-induced Osteomalacia: A Case Report and Etiological Analysis with Literature Review

BACKGROUND

Tumor-induced osteomalacia (TIO) belongs to a rare disease of the paraneoplastic syndrome. Phosphate uric mesenchymal tumor (PMT) is the most common cause of TIO, while the possibility of other tumors cannot be excluded.

CASE PRESENTATION

We present a case of a 36-year-old female patient with systemic skeletal abnormalities. The woman complained of low back pain with mild motor dysfunction for 2 years. Laboratory examination showed abnormalities in markers of bone metabolism, parathyroid hormone (PTH), vitamin D and serum phosphorus. Pooled imaging examination indicated extension abnormalities in the skeletal system and a single lesion in the right femoral head. The lesion of the right femoral was imaging with somatostatin receptor-positive, which was highly suggestive of a single neuroendocrine tumor. CT guided right femoral tumorectomy and bone grafting were performed when medical treatment failed. Postoperative pathological diagnosis was phosphate urinary mesenchymal tumor secreting fibroblast growth factor 23 (FGF23), which accorded with pre-operative expectations. The postoperative symptoms were effectively relieved, and indicators returned to normal.

CONCLUSION

The tumors causing TIO exhibited significant heterogeneity in terms of tissue origin, pathological characteristics and biological behavior, but the unique common characteristic is the secretion of FGF23. With significant progress in diagnosis and treatment, the clinical follow-up of most TIO patients shows a good prognosis, but the prognosis of those with malignant tumors is relatively poor.

Lung Nodule as Culprit Lesion Causing Recurrent Tumor-Induced Osteomalacia Revealed by 68Ga-DOTATATE PET/CT

ABSTRACT

Neoplasms that cause tumor-induced osteomalacia are very rarely located in the lung. A 27-year-old man underwent a surgery in the right femoral head to remove the tumor that induced osteomalacia 8 years ago with complete symptomatic relief. However, his bone pain occurred again recently, which lead to suspicion of a recurrent tumor-induced osteomalacia. 68Ga-DOTATATE PET/CT images showed a pulmonary nodule with mildly increased uptake along with increased activity in the left foot. The pulmonary nodule was subsequently resected and was pathologically confirmed as a phosphaturic mesenchymal tumor. The symptoms were completely relieved postsurgery.

Unexpected Phosphaturic Mesenchymal Tumor of the Femoral Head

Osteonecrosis of femoral head (ONFH) is clinically common and easily diagnosed via imaging examination, especially when there is a definite cause, such as a fracture, long-term hormonotherapy, etc. However, some rare neoplastic lesions of the femoral head can mimic its image performance in some situations, leading to misdiagnosis. We present the case of a 57-year-old male with bone pain in the left hip joint that persisted for 2 years. CT and MRI images were performed and both were suggestive of ONFH. Unexpectedly, the histopathologic results of left proximal femur resection revealed the diagnosis of phosphaturic mesenchymal tumor (PMT), a rare mesenchymal tumor. His hip pain was obviously relieved after surgery, and the course of 1-year follow-up was uneventful.

Phosphaturic Mesenchymal Tumors: Rethinking the Clinical Diagnosis and Surgical Treatment

BACKGROUND

The diagnosis of phosphaturic mesenchymal tumors (PMT) is easily delayed clinically, and their surgical treatment is unstandardized. This study aimed to evaluate our experience in the diagnosis and treatment of PMT and provide a research basis for the accurate and standardized treatment of PMT.

MATERIALS AND METHODS

Twelve patients diagnosed with PMT in our department and who underwent surgical treatment were included in this study. Preoperative demographic and clinical information were recorded. CT, MRI, and technetium-99m (Tc99m)-octreotide PET/CT imaging techniques were used to evaluate the general conditions and lesion boundaries of the tumors. Surgical treatment was performed using radical resection and microwave ablation-assisted extended curettage according to the lesion location and size. Patients were strictly followed up with and evaluated for oncological prognosis, radiological results, bone healing, serum ion levels, limb function, and pain level; the occurrence of complications was also recorded.

RESULTS

Three patients underwent radical resection, and nine underwent microwave ablation-assisted extended curettage. The average duration of symptoms in this group was 1.5 years (9-35 months) before diagnosis. Serum phosphate and AKP levels returned to normal one and two weeks postoperatively, respectively. There was no apparent specificity in the pathological findings; however, the immunohistochemistry of FGF-23 was positive, and the original fracture sites were effectively healed during the follow-up. The limb function and pain scores were significantly improved. The MSTS score increased from 15.3 to 29.0, and the VAS score decreased from 5.3 to 0.4. All patients recovered, and 90% resumed their original jobs.

CONCLUSIONS

Accurate diagnosis and standardized surgical treatment are crucial to achieving a clinical cure for PMT. Combining clinical manifestations, biochemical examinations, imaging characteristics, and pathological findings is an effective way to diagnose PMT accurately. Radical resection and microwave ablation-assisted extended curettage are reliable surgical treatment methods for PMT.