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Phosphaturic mesenchymal tumors (PMTs) are extremely rare mesenchymal tumors of soft tissue and bone that cause tumor-induced osteomalacia (TIO). Some of these tumors are completely asymptomatic and may grow undetected unless they become large enough to cause pain or discomfort. This type of tumor is crucial to diagnose in patients being treated for phosphate metabolism disorders and are a rare reason why patients seek medical help owing to pain. Here, we report the details of a patient with progressive bone pain caused by a PMT originating in the left femur., Competing Interests: Declaration of conflicting interestsThe authors declare that there is no conflict of interest.

Tumor-induced osteomalacia (TIO) is a disorder in which the clinical signs and symptoms of osteomalacia and the biochemical abnormalities of hypophosphatemia, phosphaturia, and low serum levels of 1,25(OH)2 Vitamin D3 are secondary to a neoplasm. A 33-year-old woman presented with musculoskeletal pain and proximal myopathy with a duration of 2.5 years which was treated with Vitamin D supplements. On the basis of the biochemical tests and histopathology, she was reevaluated and found to have TIO secondary to a phosphaturic mesenchymal tumor. The tumor was resected (limb salvage with endoprosthesis), and she had no pain or weakness at followup. The case reminds the readers to consider the possibility of TIO when evaluating patients with isolated hypophosphatemia, which may lead to long-term disability and prolonged morbidity if untreated. Early recognition and diagnosis of TIO is crucial since resection of the tumor usually reverses its manifestations., (Copyright © 2023 Copyright: © 2023 Saudi Journal of Kidney Diseases and Transplantation.)

Oncogenic osteomalacia (OO) is an uncommon paraneoplastic syndrome occurring due to the presence of a tumour that oversecretes fibroblast growth factor-23, which impairs renal phosphate handling. In most cases, the tumour is a morphologically distinct entity called 'phosphaturic mesenchymal tumour' (PMT). Spinal tumours causing OO are exceedingly rare. A 55-year-old man presented with multiple bone pain and proximal muscle weakness in the lower limbs. The constellation of biochemical findings (hypophosphataemia, normocalcaemia, increased alkaline phosphatase, low-normal serum vitamin D and hyperphosphaturia) with radiographical rarefaction of the skeleton and pseudofractures led us to consider OO as a possibility. Functional imaging ( 68 Ga DOTA-NOC positron emission tomography/CT scan) localised the tumour to the D2 vertebra. Complete surgical resection led to resolution of symptoms, improved ambulatory status, normalisation of biochemical parameters and healing of pseudofractures. PMT should be considered in the differential diagnosis of hypophosphataemic osteomalacia with hyperphosphaturia. Tumour localisation with functional imaging and complete surgical resection produces satisfactory outcome., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2020. No commercial re-use. See rights and permissions. Published by BMJ.)

Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome of certain mesenchymal tumors which secrete fibroblast growth factor-23 (FGF-23) responsible for causing features of hypophosphatemia and osteomalacia in these patients. Most of them involve the appendicular skeleton and occasionally the craniofacial regions. Involvement of spine is exceedingly rare. Through this paper, the authors present a rare case of a 71-year-old male with TIO due to a lesion in the cervical spine (right C2 lamina) which was proven to be a phosphaturic mesenchymal tumor-mixed connective tissue type on histopathology. This is the fifth reported case of TIO localized to the cervical spine. The patient underwent a hemilaminectomy and gross total resection of the tumor following which he made a gradual but steady recovery and does not have any recurrence 24 months after surgery. The authors not only provide a comprehensive literature review of all 18 spinal cases reported till date but also discuss the management of these patients in light of the published literature., Competing Interests: None

Tumor-induced osteomalacia causing by phosphaturic mesenchymal tumor of the foot is exceedingly rare, thus may bring great challenges to the timely and proper diagnosis and treatment of clinicians. The only definitive management is removal of the phosphaturic mesenchymal tumor completely. The objective of this article is to report 2 unusual cases with tumor-induced osteomalacia causing by phosphaturic mesenchymal tumor of the foot.We describe 2 patients with phosphaturic mesenchymal tumor involving the foot who were successfully treated with tumor resection. On presentation to our institution, the patients both had signs of severe osteomalacia, and the patients' most outstanding complaints were diffuse bone pain, general weakness, and disabled walking. A 53-year-old female underwent surgical excision of pathogenic tumor on the sole of left foot. A 62-year-old female underwent complete excision of pathogenic tumor of right plantar. The patients showed appropriate destruction of the tumor, adequate pain relief, and the elevated blood phosphorus levels compared with the previous status.Surgical resection is the most effective treatment option for patients with tumor-induced osteomalacia who can undergo appropriate surgical treatment. This represents a safe and reasonable approach to sustainably relieve pain and other symptoms with tumor-induced osteomalacia in the foot.

Information on the heterogeneity of phosphaturic mesenchymal tumor, a rare entity associated with tumor-induced osteomalacia, is limited. In this retrospective analysis of 222 phosphaturic mesenchymal tumors, 22 cases exhibited mixed mesenchymal and epithelial elements, which we propose to term "phosphaturic mesenchymal tumor, mixed epithelial, and connective tissue type." Phosphaturic mesenchymal tumor of the mixed epithelial and connective tissue type showed a distinctive and significant male predominance (male:female = 2.67:1), with most patients diagnosed at <40 years old. Moreover, all tumors were mainly located in the alveolar bone with focal invasion into surrounding soft tissue and oral mucosa, which could be detected preoperatively by oral examination. The mesenchymal component, composed of spindled cells resembling fibroblasts or myofibroblasts arranged in a storiform or fascicular pattern, exhibited a less prominent vasculature and lower cellularity than the typical phosphaturic mesenchymal tumor (mixed connective tissue type). The epithelial component was typically haphazardly and diffusely distributed throughout the tumor, forming small, irregular nests resembling odontogenic epithelial nests. All cases were immunoreactive for fibroblast growth factor-23, somatostatin receptor 2A, and NSE in both components. Mostly also demonstrated positive staining for CD99 (21/22, 96%), CD56 (16/22, 73%), Bcl-2 (21/22, 96%), and D2-40 (19/22, 86%) in one or both components. S100 was positive in both components in one of seven cases. Interestingly, immunoreactivity was typically stronger and more diffuse in the epithelial than in the paired mesenchymal components. The mesenchymal component was also diffusely positive for CD68 (17/17, 100%) and showed variable focal staining for SMA (15/22, 68%) and CD34 (9/19, 47 %). These results indicate that phosphaturic mesenchymal tumor of the mixed epithelial and connective tissue type has distinctive clinicopathological characteristics and a polyimmunophenotypic profile.

Introduction: Oncogenic osteomalacia is a very rare disease usually caused by a phosphaturic mesenchymal tumor, particularly the "mixed connective tissue type", secreting FGF-23 hormone., Objective: The authors report a case of ethmoid tumor associated with oncogenic osteomalacia and discuss management based on a review of the literature., Case Summary: A 41-year-old woman with multiple fractures causing major disability was diagnosed with early-onset osteoporosis. CT scan followed by MRI, performed due to the concomitant presence of nasal obstruction, showed a right ethmoid tumor in contact with the dura mater and periorbital tissues, but with no signs of invasion. Endoscopic resection was performed with reconstruction of the defect of the cribriform plate by a nasoseptal flap. Nasal and bone symptoms subsequently resolved. Histological examination revealed a phosphaturic mesenchymal tumor., Discussion: Twelve cases of mesenchymal tumor of the ethmoid sinus associated with oncogenic osteomalacia have been reported to date. FGF-23 assay and whole-body MRI with STIR sequence are useful for the diagnosis. A very favorable outcome is observed after surgical treatment in the majority of cases., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

Phosphaturic mesenchymal tumor (PMT) is a rare neoplasm; however, it is the most common cause of tumor-induced osteomalacia (TIO), a paraneoplastic syndrome characterized by renal phosphate wasting and hypophosphatemia. A subset of PMTs harbours an FGFR1 translocation although this alteration has not been demonstrated in PMT involving a head and neck site. We present a series of five PMTs involving the head and neck and demonstrate the diagnostic utility of fluorescence in situ hybridization (FISH) for detecting FGFR1 translocations. Patients' age and sex, tumor location, original diagnosis, the duration of symptoms, the presence of TIO, biochemical results, and medical management were reviewed. The median age at presentation was 45 (range, 24-58 years) and TIO was present in three cases. Four tumors involved soft tissue and one involved bone. Four out of the five tumors in our series were initially misdiagnosed. Three tumors were ultimately categorized as malignant PMT (two patients developed metastatic disease). FGFR1 translocation was present in two out of four cases and remained unknown in one case. In summary, we report on five cases of PMTs arising in the head and neck and confirm utility of FGFR1 FISH in the diagnosis of a subset of PMT.

Phosphaturic mesenchymal tumor (PMT) is a rare neoplasm that secretes fibroblast growth factor-23 (FGF-23) and causes oncogenic osteomalacia. It occurs in adults with equal gender distribution and the most common location is the lower extremities, followed by the head and neck. Besides osteomalacia, the clinical presentation includes bone pain and multiple bone fractures. Microscopic features consist of spindle cells, multinucleated giant cells, and calcifications embedded in a chondromyxoid matrix. Laboratory findings indicate normal calcium and parathyroid levels, hypophosphatemia, and increased levels of FGF-23 that usually revert to normal after surgical removal. Due to its rarity, the purpose of the study was to report 2 new oral cases of PMT and to review the literature in the head and neck. The first case occurred in the gingiva and had been present for 6 years. The second case was a recurrence of a previously diagnosed PMT in the right mandible that metastasized to the lung and soft tissue. The literature review included 53 cases in the head and neck. There was a predilection for extra-oral sites (76%) compared to intra-oral sites (24%) with paranasal sinuses considered the most common location (38%) followed by the mandible (15%). There were 9 recurrences that included 3 malignant cases indicating a potentially aggressive tumor. Due to the indeterminate biological behavior of PMT and its rarity, a comprehensive evaluation of medical, laboratory, radiographic, and histological findings are crucial for a definitive diagnosis and treatment.

Background: Tumor-induced osteomalacia is a paraneoplastic syndrome resulting in renal phosphate wasting and decreased bone mineralization. Phosphaturic mesenchymal tumors represent a rare etiology of tumor-induced osteomalacia. Nonspecific symptoms of fatigue, bone pain, and musculoskeletal weakness make the diagnosis elusive and lead to a delay in surgical treatment., Questions/purposes: In this case series, the following three questions were asked: (1) How do the clinical presentation and features of phosphaturic mesenchymal tumors delay the diagnosis? (2) What is the clinical course after surgical treatment of phosphaturic mesenchymal tumors? (3) How frequently do phosphaturic mesenchymal tumors recur and are there factors associated with recurrence?, Methods: This study retrospectively reviewed the cases of five adults diagnosed and treated for phosphaturic mesenchymal tumors. Patients were identified through an internal orthopaedic oncology database with clinical, surgical, and histologic data obtained through a systematic chart review., Results: Five patients presented with a long-standing history of osteomalacia, generalized fatigue, pain, and weakness before the diagnosis was reached at an average of 7.2 years (range, 2-12 years) after initial symptom onset. The diagnosis appeared to be delayed owing to the cryptic medical presentation, difficulty in locating tumor by imaging, and confirming histologic appearance. Two patients treated with wide surgical resection did not experience recurrence compared with three patients who did show recurrent signs and symptoms after marginal excision. A postoperative increase in fibroblast-derived growth factor-23 was associated with recurrent disease., Conclusions: Although uncommon, the diagnosis of phosphaturic mesenchymal tumor should be considered in any patient who presents with hypophosphaturic osteomalacia and no other physiologic cause. Definitive treatment is early, wide surgical resection.

We present 2 cases of tumor-induced osteomalacia (TIO). Both patients had histories of long-term bone and muscle pain. Laboratory data revealed hypophosphatemia. Whole-body magnetic resonance (MR) imaging (WB-MRI) clearly depicted a small subcutaneous mass in the left thigh of the first patient and a right acetabular mass in the second patient. These lesions were pathologically proven to be hemangiopericytoma-phosphaturic mesenchymal tumors (PMT).

Context: Tumor-induced osteomalacia is a rare condition usually caused by benign mesenchymal tumors. When the tumor can be found, patients are usually managed by wide excision of the tumor., Objective: We report a 51-yr-old male with clinical and biochemical evidence of tumor-induced osteomalacia caused by a mesenchymal tumor in the right iliac bone. He declined surgery and appears to have been successfully managed by computed tomography-guided percutaneous ethanol ablation and percutaneous cryoablation., Results: Our patient appears to have had an excellent clinical and biochemical response to computed tomography-guided percutaneous ethanol ablation and percutaneous cryoablation. We found one prior case of image-guided ablation using radiofrequency ablation for tumor-induced osteomalacia., Conclusions: Although the standard treatment for tumor-induced osteomalacia is wide excision of the tumor, image-guided ablation may be an option in patients who cannot have appropriate surgery or who decline surgery.

Tumor-induced osteomalacia (TIO), or oncogenic osteomalacia (OOM), is a rare acquired paraneoplastic disease characterized by renal phosphate wasting and hypophosphatemia. Recent evidence shows that tumor-overexpressed fibroblast growth factor 23 (FGF23) is responsible for the hypophosphatemia and osteomalacia. The tumors associated with TIO are usually phosphaturic mesenchymal tumor mixed connective tissue variants (PMTMCT). Surgical removal of the responsible tumors is clinically essential for the treatment of TIO. However, identifying the responsible tumors is often difficult. Here, we report a case of a TIO patient with elevated serum FGF23 levels suffering from bone pain and hypophosphatemia for more than three years. A tumor was finally located in first metacarpal bone by octreotide scintigraphy and she was cured by surgery. After complete excision of the tumor, serum FGF23 levels rapidly decreased, dropping to 54.7% of the preoperative level one hour after surgery and eventually to a little below normal. The patient's serum phosphate level rapidly improved and returned to normal level in four days. Accordingly, her clinical symptoms were greatly improved within one month after surgery. There was no sign of tumor recurrence during an 18-month period of follow-up. According to pathology, the tumor was originally diagnosed as "lomangioma" based upon a biopsy sample, "proliferative giant cell tumor of tendon sheath" based upon sections of tumor, and finally diagnosed as PMTMCT by consultation one year after surgery. In conclusion, although an extremely rare disease, clinicians and pathologists should be aware of the existence of TIO and PMTMCT, respectively.

One of the most unusual and uncommon types of osteomalacia is the oncogenic osteomalacia that is predominantly caused by a soft tissue or bone tumour, mostly by a phosphaturic mesenchymal tumour, mixed connective tissue type (PMTMCT). We report a case of a 27-year-old male presented with complaints of progressive and generalized muscle weakness, bone pains and multiple fractures. Intra-articular PMTMCT of the knee was diagnosed and surgically removed. We describe histopathological features of PMTMCT and review the most recent studies concerning this diagnostic problem.

A 45-year-old man was admitted to our hospital because of bone pain and hypophosphatemia. He had undergone surgery 2 years previously for a "benign unclassified mesenchymal tumor" in the skull, but there were no clinical symptoms related to osteomalacia. His laboratory examination revealed low serum phosphate, high alkaline phosphatase, and normal calcium levels. The diagnosis of tumor-induced osteomalacia due to phosphaturic mesenchymal tumor mixed connective tissue variant (PMTMCT) was made by re-examining the pathologic specimens. Oral supplementation with phosphate and 1-25-dihydroxyvitamin D relieved his clinical symptoms and laboratory values returned to normal. However, subcutaneous administration of octreotide had no clinical effect. Clinicians and pathologists should be aware of the existence of PMTMCT especially nonphosphaturic or asymptomatic variants of this disorder.

Osteomalacia induced by tumor is a rare phenomenon in which the resection of tumor is followed by dramatic amelioration of clinical signs and symptoms. We hereby report a case of a 66 years old male who presented with features of osteomalacia in which the characteristic clinical presentation was associated with the phosphaturic mesenchymal tumor, mixed connective tissue variant. The case is reported for its rarity.

Oncogenic osteomalacia, which is characterized by renal phosphate wasting, low serum 1, 25-dihydroxyvitamin D, and osteomalacia, is caused by mesenchymal neoplasms that are termed phosphaturic mesenchymal tumors (PMTs). As PMTs are usually small and lack specific histological features, the pathological identification of PMTs is difficult. Dentin matrix protein 1 (DMP1) is an acidic phosphoprotein expressed in mineralized tissues including bone, tooth, and hypertrophic cartilage. Increased expression of DMP1 gene in PMTs has been reported by using differential cDNA screening. In the present study, DMP1 expression in PMTs and other soft tissue tumors was analyzed immunohistochemically to verify its utility in the differential diagnosis of PMTs. Anti-DMP1 polyclonal antibody was raised against the C-terminal sequence of DMP1. Three cases with PMTs and 11 other soft tissue tumors (two malignant hemangiopericytomas, three solitary fibrous tumors, three synovial sarcomas, and three malignant peripheral nerve sheath tumors) were analyzed for DMP1 expression. DMP1 expression was observed in all of the three cases with PMTs, but never found in other soft tissue tumors examined. DMP1 was detected in the extracellular matrix with myxomatous features or around capillary vessels, and in dystrophic calcified sites. Paranuclear DMP1 staining in the tumor cells was also observed. These findings indicate that DMP1 immunohistochemistry is a useful tool for identifying PMTs.

The August 2003 COM. A 47-year-old woman presented with a long history of muscle pain, weakness, and visual disturbances. Over the last year, she developed diplopia and left sixth nerve palsy. No other neuro-ophthalmologic abnormalities were found. Past medical and family history was unremarkable. Laboratory investigation disclosed hypophosphatemia, phosphaturia, elevated serum alkaline phosphatase activity, and normal serum calcium levels. CT scans showed a lobulated mass arising on the meningeal surface of the cavernous sinus, measuring 3x 2 x 2 cm. The lesion was partially resected and microscopic examination revealed a highly vascularized tumor composed of primitive mesenchymal cells arranged whether in a patternless-pattern or surrounding thin-walled, branching vascular spaces and thick-walled hyalinized vessels. Other eye-catching features were microcystic areas, multinucleated osteoclastic-like giant cells, scattered islands of mature adipocytes, foci of hemorrhage, thrombosed medium-sized-to-large vessels, and hemosiderin-laden macrophages. After surgery, the patient recovered from the muscle pain and weakness, with a significant improvement of serum calcium and alkaline phosphatase levels and phosphate blood levels. Taken together, the clinical and pathologic features were consistent with a diagnosis of phosphaturic mesenchymal tumor (mixed connective tissue variant) of the cavernous sinus in a setting of oncogenic osteomalacia. No further treatment was carried out. The patient has been followed for the last 4 years with no evidence of recurrent disease. Oncogenic osteomalacia is a rare clinical entity characterized by hypophosphatemia, phosphaturia, and a low concentration of 1,25-dihydroxyvitamin D(3) caused by a neoplasm. Pathologists should be aware of this entity, because surgical excision of the tumor is usually curative.

The February COM. A 53-year-old obese man presented with new onset seizures and an MRI scan revealed a large cystic and necrotic heterogeneously enhancing left frontal mass. Craniotomy revealed a firm subdural tumor on the cortical surface that was delivered en-bloc preserving the pial planes and stripping it from the falx cerebri. The tumor consisted of multiple irregular fragments of white-tan rubbery tissue admixed with globules of bosselated, white-tan rubbery tissue and a fragment of bone. Sections of the tumor revealed mature hyaline cartilage with no atypia of the chondrocytes. There was focal mineralization and endochondral ossification. A diagnosis of intracranial mesenchymal osteochondroma was made. Osteochondroma, a benign cartilaginous neoplasm comprised of mature hyaline cartilage with focal ossification, is the most common benign bone tumor. Extraskeletal (mesenchymal) osteochondromas are known to originate from non-skeletal or non-cartilaginous tissue. Intracranial osteochondromas are uncommon, typically arising from the base of the skull. Only about 15% of intracranial osteochondromas arise supratentorially, from the dura, usually in a parafalcine frontoparietal location and some have been a component of Maffucci's syndrome and Ollier disease. Intracranial osteochondromas can occur at any age with a predilection for younger individuals. Intracranial mesenchymal osteochondromas exhibit a benign clinical course. Typically, the histomorphology resembles mature hyaline cartilage without anaplastic proliferation of chondrocytes or nuclear atypia, with a lobular arrangement of clusters of lacunae containing single chondrocytes. Transition to osteochondrosarcoma has rarely been documented.

Oncogenic hypophosphataemic osteomalacia is a rare condition. The causative tumour is often difficult to locate. Primary tumours have been reported in the head and neck, skeleton, and soft tissue. Octreotide scanning was used in this case and detected a mesenchymal tumour in the pubic symphysis.

The gene mutated in autosomal dominant hypophosphatemic rickets (ADHR), a phosphate wasting disorder, has been identified as FGF-23, a protein that shares sequence homology with fibroblast growth factors (FGFs). Patients with ADHR display many of the clinical and laboratory characteristics that are observed in patients with oncogenic hypophosphatemic osteomalacia (OHO), a disorder thought to arise by the secretion of a phosphate wasting factor from different mesenchymal tumors. In the present studies, we therefore investigated whether FGF-23 is a secreted factor and whether it is abundantly expressed in OHO tumors. After transient transfection of OK-E, COS-7, and HEK293 cells with the plasmid encoding full-length FGF-23, all three cell lines efficiently secreted two protein species into the medium that were approximately 32 and 12 kDa upon SDS-PAGE and subsequent Western blot analysis using an affinity-purified polyclonal antibody to FGF-23. Furthermore, Northern blot analysis using total RNA from five different OHO tumors revealed extremely high levels of FGF-23 mRNA, and Western blot analysis of extracts from a sixth tumor detected the 32 kDa FGF-23 protein species. In summary, FGF-23, the gene mutated in ADHR, is a secreted protein and its mRNA is abundantly expressed by several different OHO tumors. Our findings indicate that FGF-23 may be a candidate phosphate wasting factor, previously designated "phosphatonin".

Tumor-induced osteomalacia is characterized by paraneoplastic defects in vitamin D metabolism, proximal renal tubular functions, and phosphate transport. The resulting hypophosphatemia can cause generalized pain and muscle weakness, which significantly affect the quality of life of the patients. Palliative treatment with calcium, vitamin D, and phosphate replacement is indicated for patients in whom the causative tumor cannot be completely resected. In this report we describe a case of tumor-induced osteomalacia in whom adequate oral doses of phosphate could not be used because of gastrointestinal side-effects. Long term (3-6 months) iv phosphate infusion delivered by ambulatory infusion pumps in combination with oral calcium and vitamin D was used successfully to decrease pain and increase muscle strength. Careful monitoring of serum calcium, phosphate, and creatinine levels and reliable microinfusion technology have allowed the long term use of iv phosphate infusion without serious morbidity. This patient received repeated (three times) phosphate infusions over 8 yr, resulting in laboratory and symptomatic improvement after each course. However, this patient did suffer two episodes of central venous catheter-related infection. Because of potentially serious complications, such as severe hypocalcemia, calcified right ventricular thrombi, and nephrocalcinosis, long term iv phosphate infusion should be reserved for patients who cannot tolerate adequate doses of oral phosphate and for whom the benefits outweigh the risks.

We describe two adults with multiple cystic fibrohistiocytic tumors of the lung that manifested as bilateral nodular opacities, cystic lesions, or both on chest roentgenograms. One patient had recurrent episodes of pneumothorax and intermittent shortness of breath; the other was asymptomatic. Open-lung biopsy specimens showed identical histologically benign fibrohistiocytic proliferations associated with formation of cysts that were lined by metaplastic bronchiolar, squamous, or type II alveolar epithelium and old hemorrhage in the cysts. In both patients, the lesions grew slowly over a period of years. These unusual multiple bilateral fibrohistiocytic tumors of the lung should be included in the differential diagnosis of bilateral cystic lesions in the lung.

A 17-year-old patient with a small paratesticular embryonic sarcoma presented with symptoms of renal failure, polyuria and widespread bone metastases. Investigation revealed hypercalcaemia and uraemia without any evidence of hyperparathyroidism. The hypercalcaemia responded over a period of weeks to administration of mithramycin with initial improvement in the symptoms and metabolic derangements. Control was lost with the necrosis of intra-abdominal tumour deposits and haemorrhagic polypoid deposits in the alimentary tract. The value and hazards of mithramycin are well demonstrated by these rare complications of this type of tumour.