Phosphaturic mesenchymal tumor, mixed connective tissue variant, of the mandible: report of a case and review of the literature

A 50-Year-Old Man Presenting with Multiple Bone Lesions and a Diagnosis of Phosphaturic Mesenchymal Tumor of the Femur

BACKGROUND Phosphaturic mesenchymal tumor (PMT) is an extremely rare mesenchymal neoplasm that is commonly seen in bone and soft tissue. It is associated with a paraneoplastic syndrome, oncogenic osteomalacia, due to tumor-induced urinary phosphate wasting. It is demonstrated to be predominantly mediated by fibroblast growth factor 23 (FGF23)/fibroblast growth factor receptor 1 (FGFR1) axis. Clinically, PMT usually presents as a solitary lesion in the bone. The diagnosis of PMT is challenging due to its non-specific clinical manifestation, radiologic findings, and morphological features. CASE REPORT We report the case of a 50-year-old man presenting with multiple lytic bone lesions and associated pathologic fracture of the right femur, clinically suspicious for multiple myeloma or other metastatic malignant process. Resection from the right femur showed a hypercellular lesion composed of oval-to-spindled cells infiltrating the native trabecular bone with admixed multinucleated giant cells. Immunohistochemical (IHC) staining and in situ hybridization (ISH) demonstrated the tumor cells were positive for SATB2, ERG, FGFR1, and FGF23 ISH. DNA and RNA next-generation sequencing showed marked increases in mRNA levels of FGF23 and FGFR1. The constellation of clinicoradiologic, histomorphologic, IHC, and molecular findings supported a diagnosis of primary benign PMT. CONCLUSIONS This case report discusses a patient with PMT presenting with multifocal lesions due to tumor-induced osteomalacia at initial presentation. We hope that this report will increase the awareness of clinician and pathologists of PMT as a differential diagnosis in patients presenting with multifocal lytic bone lesions. In turn, this will prevent misdiagnosis and overtreatment of a typically benign process.

Phosphaturic mesenchymal tumor in right thigh: 2 cases report and literature review

Background

Phosphaturic mesenchymal tumor (PMT) is a very rare tumor of bone and soft tissue that has no specific clinical manifestations. Here we present 2 cases of PMT in the right thigh, including comparatively adequate immunohistochemistry.

Case Presentation

We described 2 cases of PMT in the right thigh with manifestations of hypophosphatemia. PET-CT examination showed that both patients had lesions with increased expression of somatostatin receptors in the right thigh. Bland cells and dirty calcified stroma were exhibited under the microscope. And immunohistochemical detection of FGF-23 was positive.

Conclusions

PMT is a very uncommon tumor for which diagnosis and treatment are often delayed. Considering the importance of surgery for the treatment of this disease, a full understanding of its clinicopathological features will facilitate the diagnosis of this disease.

Intracranial phosphaturic mesenchymal tumors. A case report and review of literature

Most osteomalacia-inducing tumors (OITs) are phosphaturic mesenchymal tumors (PMTs) that secrete fibroblast growth factor 23 (FGF23). These tumors usually occur in the bone and soft tissues, and intracranial OITs are rare. Therefore, intracranial OIT is difficult to diagnose and treat. This paper presents a case of intracranial OIT and shows a review of previous cases. A 45-year-old man underwent nasal cavity biopsy and treatment with active vitamin D₃ and neutral phosphate for hypophosphatemia. Amplification of FGF23 mRNA level within the tumor was detected. Subsequently, the surgical specimen was diagnosed with a PMT and was considered the cause of the patient's osteomalacia. The patient was referred to a neurosurgery department for the excision of the intracranial tumor extending to the nasal cavity. After tumor removal, the serum levels of FGF23 and phosphorus were normalized as compared to preoperative those. The patient remains disease-free, without additional treatment, approximately 10 years after surgery, with no tumor recurrence. As per the literature, intracranial OITs usually occur in patients aged 8-69 years. Bone and muscle pain are major complaints. Approximately 60% of the patients reported previously had symptoms because of intracranial tumors. In some cases, it took several years to diagnose OIT after the onset of the osteomalacia symptoms. Laboratory data in such cases show hypophosphatemia and elevated FGF23 levels. Because FGF23 levels are associated with the severity of osteomalacia symptoms, total tumor resection is recommended. PMT and hemangiopericytoma (HPC) are histologically similar, but on immunochemistry, PMT is negative for signal transducer and activator of transcription 6 (STAT6), whereas HPC is positive. FGF23 amplification is seen in PMTs but not in HPCs. Therefore, the analysis of FGF23 and STAT6 was helpful in distinguishing PMTs from HPCs. In cases of hypophosphatemia and osteomalacia without a history of metabolic, renal, or malabsorptive diseases, the possibility of oncogenic osteomalacia should be considered.

Persistence and recurrence in tumor-induced osteomalacia: A systematic review of the literature and results from a national survey/case series

PURPOSE

Tumor induced osteomalacia (TIO) is a rare disease of mineral metabolism, whose clinical picture is dominated by hypophosphatemia usually due to an excess of circulating FGF23 produced by small mesenchymal tumors. Data on the real prevalence of the disease are lacking, with the knowledge of the disease mainly relying on case reports and small case series. No estimate is available on the prevalence of uncured TIO.

METHODS

National multi-center, cross-sectional and retrospective study on persistent or recurrent cases of TIO followed in referral centers for bone diseases; systematic review of the published persistent and recurrent cases of TIO. Data from patients consecutively evaluated in referral Italian centers for bone diseases were collected; a PubMed search on persistent, recurrent and unoperable cases of TIO was carried out.

RESULTS

Sixteen patients (mean age at diagnosis 52.5 ± 10.6 years) with persistent (n = 6, 37,5%), recurrent (n = 7, 43.7%) or not operable (n = 3, 18.8%) TIO were described. Delay in diagnosis (2.5 ± 1.3 years) was demonstrated. All patients experienced fragility fractures or pseudofractures and disabling bone and muscle pain. BMD was significantly reduced (mean T-score -2.7 ± 1.7 and -2.7 ± 0.9 at lumbar spine and femoral neck, respectively). Fourteen patients were maintained under therapy with phosphate salts and calcitriol, while in 2 patients therapy with burosumab, an anti-FGF23 antibody, was commenced.

CONCLUSION

A significant number of patients with TIO remain either undiagnosed for tumor localization or tumor recur or persist after surgery. These patients with active disease represent possible candidates for burosumab treatment.

Phosphaturic Mesenchymal Tumor in the Maxillofacial Region: A Diagnostic Dilemma

Oncogenic osteomalacia is a rare paraneoplastic syndrome and is associated with the presence of phosphaturic mesenchymal tumor (PMT) which results in renal phosphate wasting with hypophosphatemia. In total, 95% of cases reported in upper and lower extremities and in head and neck are a rare site for these tumors. Besides osteomalacia, the clinical presentation includes bone pain and multiple bone fractures. Only fewer cases of PMT are reported in the oral cavity. The presentation of this rare case in a young patient was palatal swelling mimicking like an abscess which was clinically and by advanced imaging evaluated and histopathological findings confirmed the rare presentation. Following the surgical excision, the serum level of FGF23 rapidly decreased, hypophosphatemia improved, and the clinical symptoms greatly improved. The result suggests that the overexpressed FGF23 primary tumor in the palate was the cause of osteomalacia which is a rare entity.

Ameloblastic Fibroodontoma of Mandible Causing Tumor Induced Osteomalacia: A Case Report with Review of 88 Phosphaturic Oral Neoplasms

Tumor induced osteomalacia (TIO) is a rare paraneoplastic syndrome associated with tumors secreting fibroblast growth factor 23, which induces osteomalacia. Microscopically, these tumors most commonly show benign phosphaturic mesenchymal tumors. We report the first case of phosphaturic ameloblastic fibro-odontoma (AFO) manifesting as osteomalacia. Our index patient was a 33-year-old male who was diagnosed with TIO and AFO in the mandible was identified as the cause. Our case is unique as AFO is considered as a hamartoma. To the best of our knowledge, there is no hamartoma reported till date causing phosphaturic osteomalacia. As AFO demonstrates mixed epithelial and mesenchymal origin, we propose a new histopathological subtype of TIO-"phosphaturic tumor of mixed epithelial and mesenchymal origin". A review of literature focused on TIO caused by oral lesions revealed 88 oral neoplasms which matched our search criteria. Due to the rarity and unpredictable behavior of TIOs, a high index of suspicion, a broad diagnostic approach, detailed history and multidisciplinary investigations are crucial for establishing the definitive diagnosis and proper treatment recommendations.

Clinical, histopathologic, subtype, and immunohistochemical analysis of jaw phosphaturic mesenchymal tumors

Jaw phosphaturic mesenchymal tumors (PMTs) are a rare neoplasm with uncertain histogenesis. This study aimed to clarify the clinical and pathological features of jaw PMTs.We reviewed the clinical records of 39 patients diagnosed with PMTs in the jaws, and investigated clinical and morphologic characteristics, histologic subtypes, and immunophenotypes of all cases.Microscopic analyses revealed 2 major histologic tumor subtypes: "phosphaturic mesenchymal tumors of mixed epithelial and connective tissue" (PMTMECT), and "phosphaturic mesenchymal tumors of mixed connective tissue" (PMTMCT). PMTMECTs and PMTMCTs accounted for 29 and 10 cases of PMTs, respectively. Most PMTMECT diagnoses were made predominantly in males aged <45 years, and the incidence was similar in both the mandible and maxilla. In contrast, patients with PMTMCTs are predominantly females aged ≥45 years, and all tumors were in the mandible. Histologically, PMTMECT had lower cellularity and a more elongated and spindled mesenchymal component with less elaborate intrinsic microvasculature than PMTMCT. Immunohistochemically, the epithelia of all PMTMECTs was immunoreactive for AE1/AE3. Other immunohistochemical staining of PMTMECTs revealed positive expression of vimentin, SATB2, ERG, CD99, Bcl-2, CD56, S-100, D2-40, CD68, SMA, and CD34 in either one or both components. Immunohistochemical staining of PMTMCTs was diffusely positive for vimentin and a varied ratio of positivity for SATB2, ERG, CD99, Bcl-2, CD56, S-100, D2-40, CD68, SMA, and CD34, but negative for AE1/AE3. Most patients were cured by complete resection, except 2 patients who had repeated recurrences, one of which also had multiple metastasis.Jaw PMT can be divided into 2 major histological subtypes. PMTMECTs are more common than are PMTMCTs, and can transform into malignant PMTMCTs during the progression. PMTMECTs were more commonly observed in males and the incidence was similar in both the maxilla and mandible. PMTMCTs were almost always observed in the mandible of females. Compared with PMTMCTs, PMTMECTs have an admixture of epithelial components with less prominent vasculature and lower cellularity. There were no statistically significant differences in the expression of immunohistochemical markers except AE1/AE3 between PMTMECTs and PMTMCTs. However, immunohistochemical markers have great significance for differentiating other mesenchymal tumors.

Tumor induced osteomalacia in head and neck region: single center experience and systematic review

Tumor-induced osteomalacia in the head and neck region remains a challenging diagnosis to manage. Literature pertaining to management and outcome details remains sparse. We describe two cohorts: cohort 1 included seven patients from a single center in Western India with tumors located in paranasal sinuses (n = 3), intracranial (n = 2) and maxilla (n = 2). The unique features from our series is the management of persistent disease with radiation therapy (n = 2) and peptide receptor radionuclide therapy (PRRT) (n = 1). Cohort two has 163 patients identified from 109 publications for systematic review. Paranasal sinuses, mandible, intracranial disease, maxilla and oral cavity, in descending order, are reportedly common tumor sites. Within this cohort, mean age was 46 ± 14 years at presentation with 44.1% having local symptoms. Duration of symptoms varied from 1 to 240 months. Pre-surgery mean serum phosphorus was 1.4 ± 0.4 mg/dL and median FGF-23 levels were 3.6 (IQR:1.8-6.8) times of normal upper limit of normal. Majority (97.5%) were managed primarily with surgical excision; however, primary radiotherapy (n = 2) and surgery combined with radiotherapy (n = 2) were also reported. Twenty patients had persistent disease while nine patients had recurrence, more commonly noted with intracranial and oral cavity tumors. Surgery was the most common second mode of treatment employed succeeded by radiotherapy. Four patients had metastatic disease. The most common histopathological diagnosis reported is PMT mixed connective tissue, while the newer terminology 'PMT mixed epithelial and connective tissue type' has been described in 15 patients.

Tumor-induced hypophosphatemic osteomalacia caused by a mesenchymal tumor of the mandible managed by a segmental mandibulectomy and microvascular reconstruction with a free fibula flap

BACKGROUND

Tumor-induced osteomalacia is a rare paraneoplastic syndrome in which patients develop hypophosphatemia and osteomalacia.

METHODS AND RESULTS

Here, we report a unique case of a 42-year-old man who presented to our institution with a 1-year history of pain in his ribs, hips, lower back, and feet. Radiologic examination revealed a decrease in bone density and multiple insufficiency fractures. Laboratory evaluation revealed hypophosphatemia, low serum 1,25 dihydroxy vitamin D₃ , and elevated fibroblast growth factor 23 (FGF23). A positron emission tomography/CT scan showed increased uptake in the right mandibular third molar region. Panoramic radiography and CT scanning showed a lytic expansile bone lesion. A mandibular bone biopsy revealed a mixed connective tissue tumor. A right segmental mandibulectomy was performed, followed by microvascular reconstruction. The resection was confirmed by normalization of serum phosphate and FGF23.

CONCLUSION

Successful management of this condition was achieved, with complete surgical resection of the tumor and reconstructive surgery.

Phosphaturic mesenchymal tumor with an admixture of epithelial and mesenchymal elements in the jaws: clinicopathological and immunohistochemical analysis of 22 cases with literature review

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.

Imaging features of phosphaturic mesenchymal tumors

OBJECTIVE

To examine the CT and MR imaging features of phosphaturic mesenchymal tumors (PMTs).

MATERIALS AND METHODS

With IRB approval, our institutional radiology/pathology database was reviewed for pathologically-proven PMTs. CT and MRI examinations were reviewed in consensus noting several imaging features, and if available, comparative molecular imaging tests were analyzed.

RESULTS

We identified 39 patients (21 male, 18 females) with 40 PMTs [mean age, 52.9 ± 14.9 years (range, 14-78)], including 20 bone and 20 soft tissue lesions. Mean maximal lesion diameter was 3.4 ± 2.0 cm (range, 1.1-9.8). 12/18 primary bone lesions (66.6%) were osteolytic and 15/20 (75.0%) had a narrow zone of transition. Internal matrix was present in 18/32 (56.3%) lesions. PMTs were most commonly T1 isointense (31/37, 83.8%), T2 hyperintense (14/36, 38.9%), and solidly enhancing (21/30, 70.0%). The majority (32/36, 88.9%) contained areas of dark T2 signal. 8/9 PMTs were positive by ^99mTc-sestamibi scintigraphy, 2/4 by ¹¹¹In-pentetreotide scintigraphy, 2/2 by ⁶⁸Ga-DOTATATE PET/CT and 11/13 by ¹⁸F-FDG PET/CT. On FDG PET/CT, the mean SUVmax was 4.1 ± 2.5 (range, 1.5-10.8).

CONCLUSIONS

Osseous PMTs are commonly osteolytic with a narrow zone of transition. Both bone and soft tissue PMTs often contain matrix and areas of dark T2 signal on MRI, independent of the presence of matrix. However, PMTs may mimic other bone and soft tissue neoplasms, including fibrous dysplasia, tenosynovial giant cell tumor, and even atypical lipomatous tumor. As such, clinical presentation and laboratory correlation are critical to PMT recognition and accurate diagnosis.

Phosphaturic mesenchymal tumor and related wound problem

INTRODUCTION

Phosphaturic mesenchymal tumor mixed connective tissue type (PMT/MCT) is the most common type (up to 90%) of phosphaturic mesenchymal tumor (PMT), a rare clinicopathologic entity. Besides overproduction of fibroblast growth factor 23 (FGF23), there is a big variation of immunohistochemical characteristic across types of PMT, which makes it difficult to obtain an early diagnosis of PMT/MCT. As a benign tumor, PMT/MCT usually happens in subcutaneous tissues and leads to nonhealing of wound. A complete excision of PMT/MCT facilitates wound healing.

CONCLUSIONS

Review of the existing evidence indicates that early diagnosis of PMT/MCT is critically important when treating PMT/MCT wound. Hence standardization of early diagnosis for PMT/MCT is mandated.

Phosphaturic mesenchymal tumor, an unusual localization in head and neck

Phosphaturic mesenchymal tumor (PMT) is a rare mesenchymal neoplasm associated with tumor-induced osteomalacia involving bone and soft tissue that produces paraneoplastic hypophosphatemic osteomalacia. The common physiologic defect in this conditions involves an impairment in renal tubular phosphate reabsorption with a downregulation of renal 1α-hydroxylase activity, while calcium metabolism remains essentially unaffected. Microscopic features consist of spindle cells, multinucleated giant cells and calcifications embedded in a chondromyxoid matrix with variable cellularity and prominent vascularity. Approximately 95% of PMTs involve the extremities and appendicular skeleton, with only 5% occurring in the head and neck region. Localization in the head and neck is pretty uncommon, nose and paranasal sinuses are preferentially affected. Due to its rarity, the purpose of the study was to report a new case of PMT whose locations in temporomandibular joint was never reported in literature.

CT and MR imaging features in phosphaturic mesenchymal tumor-mixed connective tissue: A case report

Phosphaturic mesenchymal tumor-mixed connective tissue (PMT-MCT) is rare and usually benign and slow-growing. The majority of these tumors is associated with sporadic tumor-induced osteomalacia (TIO) or rickets, affect middle-aged individuals and are located in the extremities. Previous imaging studies often focused on seeking the causative tumors of TIO, not on the radiological features of these tumors, especially magnetic resonance imaging (MRI) features. PMT-MCT remains a largely misdiagnosed, ignored or unknown entity by most radiologists and clinicians. In the present case report, a review of the known literature of PMT-MCT was conducted and the CT and MRI findings from three patient cases were described for diagnosing the small subcutaneous tumor. Typical MRI appearances of PMT-MCT were isointense relative to the muscles on T1-weighted imaging, and markedly hyperintense on T2-weighted imaging containing variably flow voids, with markedly heterogeneous/homogenous enhancement on post contrast T1-weighted fat-suppression imaging. Short time inversion recovery was demonstrated to be the optimal sequence in localizing the tumor.

Phosphaturic Mesenchymal Tumor: 2 New Oral Cases and Review of 53 Cases in the Head and Neck

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.

Tumor-Induced Osteomalacia: an Up-to-Date Review

Tumor-induced osteomalacia (TIO) is a paraneoplastic syndrome resulting in renal phosphate wasting and decreased bone mineralization. TIO is usually induced by small, slowly growing tumors of mesenchymal origin (phosphaturic mesenchymal tumor mixed connective tissue variant [PMTMCT]). Nonspecific symptoms including fatigue, bone pain, and musculoskeletal weakness make the diagnosis elusive and often lead to a delay in treatment. The prognosis of TIO is excellent following complete resection of the neoplasm, which leads to the rapid and complete reversal of all symptoms. If the tumor cannot be detected, treatment relies on supplementation with phosphate and active vitamin D compounds. Subsequent radiotherapy in case of incompletely resected tumors or definitive radiotherapy in unresectable tumors is an important treatment option to avoid recurrence or metastasis even though this occurs rarely. Due to the risk of recurrence or late metastases, long-term monitoring is required even in TIO patients diagnosed with a benign tumor.

Phosphaturic mesenchymal tumors. Survey of 8 cases from a single Mexican medical institution

Phosphaturic mesenchymal tumor (PMT) is a morphologically heterogeneous soft tissue and bone neoplasm, producing a paraneoplastic syndrome due to phosphate wasting. These tumors produce fibroblast growth factor 23, which is implicated in renal tubule phosphate loss. Medical records of patients seen from 1999 to 2013 with osteomalacia associated or not with a tumor were reviewed. Clinical and laboratory data, radiographic studies, and follow-up of 8 patients were tabulated. Histologic features and the immunoprofile of the tumors were analyzed. There were 208 patients with osteomalacia, but only 8 (3.84%) had osteomalacia associated with a tumor. The median age of the patients was 40 years. The tumor size ranged from 1.5 to 4 cm. Five were located in soft tissues and skin; and 3, in bones. Osteomalacia symptoms lasted from 2 to 14 years with a median of 6 years. Laboratory data showed hypophosphatemia and phosphaturia in all patients. All tumors were histologically benign. Histologically, the salient features were a hemangiopericytoid pattern, chronic hemorrhage, and microcystic areas. All neoplasms were diffusely positive for vimentin and focally positive for epithelial membrane antigen, CD34, and S-100 protein. Ki-67 was positive in approximately 10% of neoplastic cells in 2 cases and less than 1% in the remainder. We report 8 cases of PMTs producing osteomalacia, from a single third-level Mexican medical institution. These tumors occurred in soft tissues, skin, and bones. All tumors were benign, small, not easily detected by physical examination and diagnosed due to the metabolic abnormalities.

Sinonasal Phosphaturic Mesenchymal Tumor: A Rare and Misinterpreted Entity

Objectives Oncogenic osteomalacia is a paraneoplastic syndrome in which the tumor secretes a peptide-like hormone, fibroblast growth factor, resulting in urinary loss of phosphates. Methods We present the case of a 50-year-old woman with a benign phosphaturic mesenchymal tumor (PMT) involving the ethmoid sinus with obstruction of the ostiomeatal complex causing unilateral nasal airway obstruction. Results The tumor was initially thought to be an esthesioneuroblastoma based on primary pathology interpretation and on clinical and radiographic appearance. However, a benign PMT was later confirmed by further testing. Conclusion The tumor was removed entirely by the endoscopic transnasal approach, leading to a full resolution of symptoms.

Phosphaturic mesenchymal tumour mixed connective tissue variant: report of three cases with unusual histological findings

Phosphaturic mesenchymal tumour mixed connective tissue variant (PMTMCT) is a rare tumour occurring in bone and soft tissue that usually behaves in a benign manner. Elaboration of biologically active substances by this tumour gives rise to a paraneoplastic syndrome known as oncogenic osteomalacia, manifesting clinically as bone pain, generalized weakness and pathological fractures. Recognition of PMTMCT and its associated syndrome is important, as resection of the tumour in most instances results in prompt resolution of symptoms. Previously reported cases of this tumour have emphasized the consistent presence of certain histological features that are considered prerequisite for making the diagnosis of PMTMCT. We describe three cases of PMTMCT, of which two first presented with progressive symptoms of osteomalacia and one remained clinically silent aside from the symptom of a palpable lump. Our cases highlight the wide-ranging histological patterns displayed by these tumours, and draw attention to certain microscopic findings that until now have been given little if any mention. Tentacular growth pattern and satellite nodules appear to be common findings in PMTMCTs, and can make complete surgical excision of these tumours challenging. The ability of this otherwise histologically benign tumour to permeate vascular spaces has to our knowledge never been described previously. One tumour lacked the characteristic calcifying matrix of PMTMCT, suggesting that in some tumours this defining feature may be focal if not entirely absent. PMTMCT shares features with and can resemble a variety of bone and soft tissue neoplasms, requiring the surgical pathologist to be familiar with this entity.

Sinonasal phosphaturic mesenchymal tumor: Case report and systematic review

We report a case of sinonasal phosphaturic mesenchymal tumor (PMT) and conduct a systematic review of the literature to highlight a unique paraneoplastic syndrome associated with PMT. We used English language publications from Medline and Cochrane databases (1970-2013) as data sources. A systematic review of the literature was conducted. All reported cases of head and neck PMTs were included. The presence or absence of the associated paraneoplastic syndrome was noted. We found 33 cases of PMT in the head and neck reported in the literature, 17 of which occurred in the sinonasal area. Approximately 5% of all PMTs are located in the head and neck. Just greater than half are concentrated in the sinonasal area, and the remaining involve various bony and soft tissue structures of the head and neck. PMT is sometimes associated with a paraneoplastic syndrome of tumor-induced (oncogenic) osteomalacia (TIO) causing bone pain, muscle weakness, and pathologic fractures. We present the 18th reported case of sinonasal PMT. A smooth mucosa-covered midline intraseptal mass filling the posterior nasal cavity with destruction and erosion of the skull base was found in an adult male. The patient underwent successful endoscopic resection with wide negative margins and is without recurrence at 24-month follow-up. PMT is a benign, locally aggressive tumor with rare malignant transformation. Knowledge of the bony invasion and destruction caused by this tumor is essential in planning surgical resection with wide negative margins. Familiarity with the associated TIO is essential to investigate for and manage any associated bony morbidity.

Ovarian cancer-related hypophosphatemic osteomalacia--a case report

CONTEXT

Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome caused primarily by benign mesenchymal tumors. It has been associated with malignancies in rare cases. High serum levels of fibroblast growth factor (FGF) 23 reported in a group of patients with ovarian cancer had normal serum phosphate levels. There had been no ovarian cancer-related hypophosphatemic osteomalacia in a search of the literature.

OBJECTIVE

We investigated a 57-year-old woman with progressive low back pain.

DESIGN AND INTERVENTION

Clinical, biochemical, and radiological assessments were performed. The patient's serum phosphate and FGF23 levels were evaluated at baseline and after treatment for ovarian cancer.

RESULTS

The patient presented with progressive low back pain and weight loss during the previous 6 months. Imaging studies revealed low bone mineral density and multiple suspicious spinal metastatic lesions. Laboratory examination showed hypophosphatemia, hyperphosphaturia, normocalcemia, an elevated serum alkaline phosphatase level, and an elevated serum FGF23 level. Because TIO was suspected, a tumor survey was performed, and ovarian carcinoma with multiple metastasis was detected. After surgery and chemotherapy treatments for ovarian cancer, the serum phosphate and FGF23 levels returned to normal, and the low back pain improved.

CONCLUSIONS

To our knowledge, this is the first case of ovarian cancer-related hypophosphatemic osteomalacia reported in the literature. TIO should be considered in patients with ovarian cancer presenting with weakness, bone pain, and fractures. Investigation of TIO is appropriate when these patients present hypophosphatemia.

Tumor-Induced Osteomalacia: Increased Level of FGF-23 in a Patient with a Phosphaturic Mesenchymal Tumor at the Tibia Expressing Periostin

In our case, a 45-year-old male patient had multiple fractures accompanied by hypophosphatemia. FGF-23 levels were significantly increased, and total body magnetic resonance imaging (MRI) revealed a tumor mass located at the distal tibia leading to the diagnosis of tumor-induced osteomalacia (TIO). After resection of the tumor, hypophosphatemia and the increased levels of FGF-23 normalized within a few days. Subsequent microscopic examination and immunohistochemical analysis revealed a phosphaturic mesenchymal tumor mixed connective tissue variant (PMTMCT) showing a positive expression of somatostatin receptor 2A (SSTR2A), CD68, and Periostin. Electron microscopy demonstrated a poorly differentiated mesenchymal tumor with a multifocal giant cell component and evidence of neurosecretory-granules. However, the resected margins showed no tumor-free tissue, and therefore a subsequent postoperative radiotherapy was performed. The patient is still in complete remission after 34 months. Tumor resection of PMTMCTs is the therapy of choice. Subsequent radiotherapy in case of incompletely resected tumors can be an important option to avoid recurrence or metastasis even though this occurs rarely. The prognostic value of expression of Periostin has to be evaluated more precisely in a larger series of patients with TIO.

68Ga DOTA-TATE PET/CT allows tumor localization in patients with tumor-induced osteomalacia but negative 111In-octreotide SPECT/CT

Tumor-induced osteomalacia (TIO) is a paraneoplastic syndrome characterized by renal phosphate wasting, hypophosphatemia and low calcitriol levels as well as clinical symptoms like diffuse bone and muscle pain, fatigue fractures or increased fracture risk. Conventional imaging methods, however, often fail to detect the small tumors. Lately, tumor localization clearly improved by somatostatin-receptor (SSTR) imaging, such as octreotide scintigraphy or octreotide SPECT/CT. However, recent studies revealed that still a large number of tumors remained undetected by octreotide imaging. Hence, studies focused on different SSTR imaging methods such as 68Ga DOTA-NOC, 68Ga DOTA-TOC and 68Ga DOTA-TATE PET/CT with promising first results. Studies comparing different SSTR imaging methods for tumor localization in TIO are rare and thus little is known about diagnostic alternatives once a particular method failed to detect a tumor in patients with TIO. Here, we report the data of 5 consecutive patients suffering from TIO, who underwent both 111Indium-octreotide scintigraphy (111In-OCT) SPECT/CT as well as 68Ga DOTA-TATE PET/CT for tumor detection. While 111In-OCT SPECT/CT allowed tumor detection in only 1 of 5 patients, 68Ga DOTA-TATE PET/CT was able to localize the tumor in all patients. Afterwards, anatomical imaging of the region of interest was performed with CT and MRI. Thus, successful surgical resection of the tumor was achieved in all patients. Serum phosphate levels returned to normal and all patients reported relief of symptoms within weeks. Moreover, an iliac crest biopsy was obtained from every patient and revealed marked osteomalacia in all cases. Follow-up DXA revealed an increase in BMD of up to 34.5% 1-year postoperative, indicating remineralization. No recurrence was observed. In conclusion our data indicates that 68Ga DOTA-TATE PET/CT is an effective and promising diagnostic tool in the diagnosis of TIO, even in patients in whom 111In-OCT prior failed to detect a tumor.

Osteomalacia caused by skull base tumors: report of 2 cases

BACKGROUND AND IMPORTANCE

Tumor-induced osteomalacia (TIO) is an uncommon paraneoplastic syndrome rarely encountered in neurosurgical practice. We report on 2 cases of TIO caused by skull base tumors. Although the diagnosis of TIO is difficult to make and often is delayed because of the insidious nature of the symptoms, mostly systemic pain and weakness, it is curable once it is diagnosed and properly treated.

CLINICAL PRESENTATION

Both patients presented with severe pain developing in the lower extremities and moving out to the entire body, as well as difficulty moving. They were diagnosed with TIO several years after onset. A high level of serum FGF23 was confirmed, and whole-body imaging studies demonstrated tumors in the middle and anterior cranial base, respectively. The patient with the anterior cranial base tumor had a history of hemorrhage into the frontal lobe and partial resection. En bloc resection of tumor with surrounding skull bone was performed. The histological diagnosis for both cases was phosphaturic mesenchymal tumor, mixed connective tissue variant.

CONCLUSION

The level of FGF23 normalized immediately after surgery. Both patients experienced a dramatic relief of pain and recovery of muscle power. Although reports of osteomalacia caused by tumors in the neurosurgical field are extremely rare in the literature, its true incidence is unknown. We emphasize the importance of recognition of this syndrome and recommend total resection of tumors when possible.

Mandibular phosphaturic mesenchymal tumor-mixed connective tissue variant in a young girl

Phosphaturic mesenchymal tumor-mixed connective tissue variant (PMTMCT) is an extremely rare tumor associated with tumor-induced osteomalacia. The majority occur in middle age and arise from the extremities. This report describes a young girl with PMTMCT arising in the mandible and with no evidence of paraneoplastic syndrome.

Tumor-induced osteomalacia: an important cause of adult-onset hypophosphatemic osteomalacia in China: Report of 39 cases and review of the literature

Tumor-induced osteomalacia (TIO) is an acquired form of hypophosphatemia. Tumor resection leads to cure. We investigated the clinical characteristics of TIO, diagnostic methods, and course after tumor resection in Beijing, China, and compared them with 269 previous published reports of TIO. A total of 94 patients with adult-onset hypophosphatemic osteomalacia were seen over a 6-year period (January, 2004 to May, 2010) in Peking Union Medical College Hospital. After physical examination (PE), all patients underwent technetium-99m octreotide scintigraphy ((99) Tc(m) -OCT). Tumors were removed after localization. The results demonstrated that 46 of 94 hypophosphatemic osteomalacia patients had high uptake in (99) Tc(m) -OCT imaging. Forty of them underwent tumor resection with the TIO diagnosis established in 37 patients. In 2 patients, the tumor was discovered on PE but not by (99) Tc(m) -OCT. The gender distribution was equal (M/F = 19/20). Average age was 42 ± 14 years. In 35 patients (90%), the serum phosphorus concentration returned to normal in 5.5 ± 3.0 days after tumor resection. Most of the tumors (85%) were classified as phosphaturic mesenchymal tumor (PMT) or mixed connective tissue variant (PMTMCT). Recurrence of disease was suggested in 3 patients (9%). When combined with the 269 cases reported in the literature, the mean age and sex distribution were similar. The tumors were of bone (40%) and soft tissue (55%) origins, with 42% of the tumors being found in the lower extremities. In summary, TIO is an important cause of adult-onset hypophosphatemia in China. (99) Tc(m) -OCT imaging successfully localized the tumor in the overwhelming majority of patients. Successful removal of tumors leads to cure in most cases, but recurrence should be sought by long-term follow-up.

Recurrent phosphaturic mesenchymal tumour of the temporal bone causing deafness and facial nerve palsy

OBJECTIVE

We describe the first reported case of a phosphaturic mesenchymal tumour, mixed connective tissue variant, invading the temporal bone.

CASE REPORT

A female patient presented with increasing deafness. On examination there appeared to be a mass behind an intact tympanic membrane. Further radiological investigation showed a vascular mass occupying the middle ear, mastoid and internal auditory meatus. This was surgically resected and revealed to be a benign phosphaturic mesenchymal tumour, mixed connective tissue variant. The tumour recurred a year later, presenting as facial nerve palsy. A revision procedure was carried out; the tumour was excised with the sacrifice of a segment of the facial nerve, and a facial-hypoglossal nerve anastomosis was performed.

CONCLUSION

This case report highlights the occurrence of this benign but sometimes aggressive tumour, of which both clinicians and pathologists should be aware. Early recognition of the condition remains of utmost importance to minimise the debilitating consequences of long-term osteomalacia in affected patients, and to prevent extracranial and intracranial complications caused by the tumour.

Striking pathology gold: a singular experience with daily reverberations: sinonasal hemangiopericytoma (glomangiopericytoma) and oncogenic osteomalacia

Sinonasal hemangiopericytoma-like tumors(SNHPC)(glomangiopericytomas)were originally conceived as histologically similar to, but biologically distinct from, their soft tissue counterparts. Re-evaluation of "hemangiopericytiomas" has determined that SNHPC (glomangiopericytomas) represent bona-fide pericyte-derived tumors, whereas most soft tissue neoplasms previously designated as hemangiopericytomas represent cellular variants of solitary fibrous tumors or other lesions with a hemangiopericytomalike growth pattern. We present an interesting case of a woman with SNHPC (glomangiopericytomas) causing oncogenic osteomalacia, and discuss the recent advances in our understanding of phosphaturic mesenchymal tumors. This particular case is an example of "Striking Pathology Gold"-a situation where the pathologist actively guides the diagnostic process, and witnesses its repercussions. "Striking Pathology Gold" may be a rare event in one's career. However it serves to remind us of our place in the world as physicians. Working behind the scenes, we quietly change the course of countless individual destinies for the better.

Approach to the hypophosphatemic patient

Hypophosphatemia is commonly missed due to nonspecific signs and symptoms, but it causes considerable morbidity and in some cases contributes to mortality. Three primary mechanisms of hypophosphatemia exist: increased renal excretion, decreased intestinal absorption, and shifts from the extracellular to intracellular compartments. Renal hypophosphatemia can be further divided into fibroblast growth factor 23-mediated or non-fibroblast growth factor 23-mediated causes. Proper diagnosis requires a thorough medication history, family history, physical examination, and assessment of renal tubular phosphate handling to identify the cause. During the past decade, our understanding of phosphate metabolism has grown greatly through the study of rare disorders of phosphate homeostasis. Treatment of hypophosphatemia depends on the underlying disorder and requires close biochemical monitoring. This article illustrates an approach to the hypophosphatemic patient and discusses normal phosphate metabolism.

Evaluation of hypophosphatemia: lessons from patients with genetic disorders

Phosphate is a key component of several physiologic pathways, such as skeletal development, bone mineralization, membrane composition, nucleotide structure, maintenance of plasma pH, and cellular signaling. The kidneys have a key role in phosphate homeostasis, with 3 hormones having important roles in renal phosphate handling: parathyroid hormone, fibroblast growth factor 23 (FGF-23), and 1,25-dihydroxyvitamin D. Independent of the genetic diseases affecting the FGF-23 pathway (such as hypophosphatemic rickets), hypophosphatemia is a frequent condition encountered in daily practice, and untreated critical hypophosphatemia can induce hemolysis, rhabdomyolysis, respiratory failure, cardiac dysfunction, and neurologic impairment. Rapid correction thus is necessary to avoid severe complications. The aims of this teaching case are to summarize the causes and biological evaluation of hypophosphatemia and provide an overview of our current understanding of phosphate metabolism.

Phosphaturic mesenchymal tumor with chondromyxoid fibroma-like feature: an unusual morphological appearance

Phosphaturic mesenchymal tumor (PMT) is a rare and distinctive tumor almost always associated with oncogenic osteomalacia. This tumor is often misdiagnosed due to its widely varied histomorphological spectrum. More recently the term PMT or its variants has been used whatever the histomorphological features. Herein, we present a case of a 32-year-old woman who presented with a 2-year history of oncogenic osteomalacia. The clinical examination failed to detect any tumor. The F-18 FDG PET scan and subsequent MRI revealed a tumor in the soft tissues of the right popliteal fossa. The histological features resembled a chondromyxoid fibroma (CMF), a feature documented only in two cases so far.

Malignant phosphaturic mesenchymal tumor of the larynx

Phosphaturic mesenchymal tumors are rare neoplasms predominantly originating in the trunk and extremities. Malignant variants are exceedingly rare, and can present significant diagnostic challenges to the pathologist and otolaryngologist alike. This report describes the first case of malignant phosphaturic mesenchymal tumor involving the larynx, and emphasizes the importance of vigilance in both histopathologic and clinical actions so that appropriate treatment can be provided in a timely manner. The clinical presentation, radiologic and histologic features, and management are discussed.

[FGF23 and Klotho: the new cornerstones of phosphate/calcium metabolism]

Since its first description as a phosphaturic agent in the early 2000s, fibroblast growth factor 23 (FGF23) has rapidly become the third key player of phosphate/calcium metabolism after PTH and vitamin D. FGF23 is a protein synthesized by osteocytes that acts mainly as a phosphaturic factor and a suppressor of 1α hydroxylase activity in the kidney. It inhibits the expression of type IIa and IIc sodium-phosphate cotransporters on the apical membrane of proximal tubular cells, thus leading to inhibition of phosphate reabsorption. Moreover, it also inhibits 1α hydroxylase activity. These two renal pathways account together for the hypophosphatemic effect of FGF23, but FGF23 has also been recently described as an inhibiting factor for PTH synthesis. Its exact role in bone remains to be defined. A transmembrane protein, Klotho, is an essential cofactor for FGF23 biological activity, but it can also act by itself for calcium and PTH regulation. This paper gives an overview of these recent data of phosphate/calcium physiology, as well as a description of clinical conditions associated with FGF23 deregulation (genetic diseases and chronic kidney disease). As a conclusion, future therapeutic consequences of the FGF23/Klotho axis are discussed.

Tumor-induced osteomalacia

Tumor-induced osteomalacia (TIO) is a rare and fascinating paraneoplastic syndrome in which patients present with bone pain, fractures, and muscle weakness. The cause is high blood levels of the recently identified phosphate and vitamin D-regulating hormone, fibroblast growth factor 23 (FGF23). In TIO, FGF23 is secreted by mesenchymal tumors that are usually benign, but are typically very small and difficult to locate. FGF23 acts primarily at the renal tubule and impairs phosphate reabsorption and 1α-hydroxylation of 25-hydroxyvitamin D, leading to hypophosphatemia and low levels of 1,25-dihydroxy vitamin D. A step-wise approach utilizing functional imaging (F-18 fluorodeoxyglucose positron emission tomography and octreotide scintigraphy) followed by anatomical imaging (computed tomography and/or magnetic resonance imaging), and, if needed, selective venous sampling with measurement of FGF23 is usually successful in locating the tumors. For tumors that cannot be located, medical treatment with phosphate supplements and active vitamin D (calcitriol or alphacalcidiol) is usually successful; however, the medical regimen can be cumbersome and associated with complications. This review summarizes the current understanding of the pathophysiology of the disease and provides guidance in evaluating and treating these patients. Novel imaging modalities and medical treatments, which hold promise for the future, are also reviewed.

Diagnosis of phosphaturic mesenchymal tumor (mixed connective tissue type) by cytopathology

Oncogenic osteomalacia (OO) is a rare paraneoplastic condition in which a bone or soft tissue tumor induces biochemical and clinical signs and symptoms of osteomalacia (or rickets) most often by the production of the phosphaturic protein, fibroblast growth factor-23. Phosphaturic mesenchymal tumor, mixed connective tissue type (PMTMCT) is a rare, histologically distinct tumor that represents the most common cause of OO. As the clinical diagnosis of OO is typically suspected on the basis of clinical and biochemical features and the presence of a bone or soft tissue tumor, cytologic examination might potentially provide the necessary pathologic confirmation of OO. In this case of a 46-year-old female with clinical stigmata of OO and a right distal humeral mass, we report that the fine-needle aspiration findings of short, cytologically bland spindled cells embedded in a fine, fibrillary stromal-rich matrix and the presence of osteoclast-type giant cells associated with the stromal matrix provide strong pathological evidence for PMTMCT and assist in pathologically confirming the clinical impression of OO, thus alleviating the need for a more invasive diagnostic surgical procedure.

A nonphosphaturic mesenchymal tumor mixed connective tissue variant of the sacrum

Tumor-induced or oncogenic osteomalacia is a rare paraneoplastic syndrome characterized by overproduction of fibroblast growth factor-23 as a phosphaturic agent and renal phosphate wasting. A range of predominantly mesenchymal neoplasms have been associated with tumor-induced osteomalacia and classified as phosphaturic mesenchymal tumor mixed connective tissues. However, phosphaturic mesenchymal tumor mixed connective tissues could be nonphosphaturic in the first stage of the disease, either because the tumors are resected early in the clinical course or because the patient's osteomalacia was attributed to another cause. This article presents a case of a 42-year-old woman with a 2-year history of low back and right leg pain. Laboratory examinations including serum and urine calcium and phosphorous were within normal values. Imaging of the lumbar spine and pelvis showed an osteolytic lesion occupying the right sacral wing. Histology was unclear. Reverse-transcription polymerase chain reaction analysis for fibroblast growth factor-23 was positive and confirmed the diagnosis of phosphaturic mesenchymal tumor mixed connective tissues. Preoperative selective arterial embolization and complete intralesional excision, bone grafting, and instrumented fusion from L4 to L5 to the iliac wings bilaterally was performed. Postoperative recovery was uneventful. Neurological deficits were not observed. A lumbopelvic corset was applied for 3 months. At 12 months, the patient was asymptomatic. Serum and urine values of calcium and phosphorous were normal throughout the follow-up evaluation.