The phosphaturic mesenchymal tumor: why is definitive diagnosis and curative surgery often delayed?

G, Surendran S, Patinharayil G, Fazil V.V. M, K.V. N, Sudhan S. R. PTH like substance secreting mesenchymal tumor causing oncogenic osteomalacia; unravelling the difficulties in localization - A report of 2 cases

Background

Oncogenic osteomalacia is a rare paraneoplastic association of Phosphaturic mesenchymal tumor (PMT) secreting excessive levels of a PTH like substance. They usually remain undiagnosed and patients suffer for years. The rarity of this tumor and its non-specific clinical presentations poses great challenge to the treating surgeons. Its management is poorly described in literature. We report two of such rare cases without much diagnostic delay.

Case report

We had 2 cases; A 53-year-old south east Asian male with 6 months of debilitating pain over multiple sites, and another 44-year-old male patient with complaints of low back ache, and pain over both lower and upper limbs for 1.5 years. Both had low serum phosphorus and elevated FGF-23 values, but all other parameters were normal. A PMT was suspected and confirmed on a Ga68- DOTATOC scan in both cases, and on complete excision, their symptoms and the altered blood parameters got normalized. Histology was consistent with PMT.

Conclusion

Accurate and timely diagnosis of a PMT with non-specific features are extremely challenging, but not without solutions. Even though a tumor of rarity, with the appropriate imaging modalities like Ga68- DOTATOC scan, and estimation of FGF-23 and serum phosphorus levels, they can be diagnosed. Once identified, complete removal is often curative within a few months.

Clinical characteristics and surgical outcomes of vertebral lesions associated with tumor-induced osteomalacia: report of 16 patients and review of the literature

Vertebral tumors in patients with tumor-induced osteomalacia (TIO) have a low diagnostic rate and poor postoperative outcomes. The application of 68 Ga-DOTATATE-PET/CT significantly increased the detection rate. Compared with tumor curettage, segmental resection was recommended as the preferred surgical type due to its high recovery rate.

PURPOSE

Tumor-induced osteomalacia (TIO) is an acquired hypophosphatemic osteomalacia, and surgery is the first-line therapy. Most TIO tumors are found in the bones of the appendicular skeleton, cranium, and paranasal sinuses but rarely in the vertebrae. Tumor curettage and segmental resection are the two main surgical options for vertebral TIO patients. However, research on the clinical characteristics and surgical prognosis of vertebral TIO patients is rare. In the present study, for the first time, we investigated the clinical characteristics of 16 vertebral TIO patients and compared the surgical outcomes of patients who underwent surgery via two different surgical methods.

METHODS

This was a retrospective cohort study. In this study, we included 16 adult TIO patients with lesions in vertebrae from Peking Union Medical College Hospital (PUMCH), all of whom underwent surgery. Baseline laboratory data were collected through medical records review. Technetium-99 m octreotide scintigraphy (99Tcm-OCT) and 68gallium-DOTA-TATE-positron emission tomography/computed tomography (68 Ga-DOTATATE-PET/CT) were conducted at the Department of Nuclear Medicine of PUMCH. The tumor histopathology was confirmed by a senior pathologist at our center.

RESULTS

Vertebral TIO patients had lower serum phosphorus and TmP/GFR and higher serum alkaline phosphatase (ALP), serum parathyroid hormone (PTH), and serum C-terminal cross-linked telopeptide of type I collagen (β-CTX) levels than the normal range. The sensitivity of 68 Ga‒DOTATATE PET/CT was 100%, significantly greater than that of 99Tcm-OCT (40%). After comparing the outcomes between the two surgical methods, we found that the recovery rate after segmental resection (62.5%) was greater than that after tumor curettage (12.5%). In the thoracic and sacral vertebrae, segmental resection surgery had a good prognosis.

CONCLUSION

68 Ga-DOTATATE PET/CT could serve as the first diagnostic tool in patients with vertebral TIO, and segmental resection could be used as the preferred surgery. This study would raise awareness of the clinical features and management of these rare vertebral TIO patients.

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.

Challenges in the diagnosis and management of tumor-induced osteomalacia: A case report

The present case report is aimed to highlight the difficulty and the reason for the delayed diagnosis of phosphaturic mesenchymal tumors, emphasizing the need of standardized protocols for diagnosis, surgery and follow-up in high-volume hospitals. The clinical signs and symptoms, diagnostic and therapeutic procedures, immunohistological features were analyzed. Delayed diagnosis of phosphaturic mesenchymal tumor was primarily due to non-specific clinical symptoms such as fatigue, muscular and bone pain, and multiple fractures. This cryptic clinical picture made the diagnosis tricky that led to treatment of patient for non-specific pain and stress fractures before to consider the tumor-induced osteomalacia syndrome. Some well-documented studies were found in the literature in which the history of trauma is a critical trigger of glomus tumors. Extra-subungual tumors most frequently occur in the knee and ankle regions, particularly among young adults, and the diagnosis is typically made approximately 7.2 years after initial symptom onset. The difficult tumor localization represented an additional obstacle to the prompt treatment, leading to delayed curative surgery.

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.

Extended curettage for tumour-induced osteomalacia in the bone

BACKGROUND

extended curettage is generally used to treat infiltrative bone tumours. However, the extent of the curettage performed in previous studies remains unclear. This study aimed to investigate the efficacy of extended curettage for bone tumour-induced osteomalacia.

METHODS

we included 12 patients with tumour-induced osteomalacia who underwent extended curettage at our hospital between 2000 and 2022. Extended curettage was applied in cases where tumour resection could cause functional impairment or necessitate complex reconstruction. We investigated patients' clinical and oncological outcomes.

RESULTS

patients had a mean age of 55 (24-81) years, and the median follow-up duration after surgery was 3.9 (1.0-14.0) years. The causative tumours were located in the pelvis and lumbar spine. Imaging revealed the tumours to be of the sclerotic, intertrabecular, lytic and mixed types. Intraoperative 3D fluoroscopy was used in 10 patients. Extended curettage with high-speed burring and adjuvant therapy with cauterization using an electric scalpel and ethanol resulted in a remission rate of 83%; no recurrence or metastasis was observed in cases of early postoperative biochemical remission. In cases where the causative tumour was at the lumbar spine and ischium close to the acetabulum, no postoperative biochemical remission was observed, and conservative treatment was continued. Except for one patient with a tumour in the lumbar spine, all patients could walk without a cane.

CONCLUSIONS

extended curettage for bone tumour-induced osteomalacia is oncologically and functionally favourable, especially in cases where resection of the causative tumour could cause functional impairment or necessitate complex reconstruction.

Treatment and Diagnose of Spinal Phosphaturic Mesenchymal Tumor: A Case Report and a Systematic Literature Review

BACKGROUND

Spinal phosphaturic mesenchymal tumor (PMT) is a rare disorder but can be cured once the diagnosis is clear and a complete removal by surgery is performed. To the best of our knowledge, only 22 cases in the spine have been described, and we report a case with the largest number of spinal segments (T12-L5) affected among spine PMT cases.

METHODS

A comprehensive literature search was performed until May 23, 2023, following the Preferred Reporting Items for Systematic Reviews guidelines. Studies were chosen through relevant PubMed, Web of Science, and EMBASE searches to prioritize obtaining the largest studies. The Medical Subject Headings and Boolean operators employed for this search were ("PMT" or "TIO" or "Tumor-induced osteomalacia" or "phosphaturic mesenchymal tumor") and ("spine" or "spinal"). Two researchers (L.S.Z. and D.B.C) independently reviewed and evaluated the included articles. Any differing opinions were discussed until a consensus was reached. A total of 18 studies were included. A case report is also presented.

RESULTS

We report a case of spinal PMT. The full text of the relevant articles was construed. A total of 18 studies were reviewed and consolidated. These articles are roughly divided into the following 5 subcategories: 1) clinical features and baseline distribution, 2) laboratory and imaging findings, 3) pathological manifestations, and 4) surgical methods and treatment options.

CONCLUSIONS

Spinal PMT is very rare with a high rate of misdiagnosis and debilitating complications, so it is of significance to increase awareness of the disease among spine surgeons consulted by patients with spinal PMT. 68Ga-DOTATOC-PET/CT shows very high sensitivity to the spinal PMT but there is no way to exactly determine the location of the tumor. PMT has unique immunohistochemical characteristics and malignant PMT is rare. Once diagnosed, complete surgical excision is the recommended treatment. Burosumab is one of the available options, especially in cases that are recurrent and difficult to surgically resect.

Phosphaturic mesenchymal tumor: Clinicopathological features with outcomes in 10 patients with review of literature

BACKGROUND

Phosphaturic mesenchymal tumors (PMTs) are rare mesenchymal tumors, associated with long-standing, non-specific but often debilitating symptoms in the affected patients. These tumors display characteristic histopathological features and in case, identified timely, can be a boon for patients, given an excision is completely curative.

AIMS

To evaluate the clinical and histopathological features of 10 PMTs, diagnosed at our institution, along with clinical outcomes in those patients.

MATERIALS AND METHODS

This was a retrospective study, wherein 10 PMTs, diagnosed from January 2013 to July 2022, were included.

RESULTS

The average age at the time of diagnosis was 40 years with an M:F ratio of 4:1. Clinical features included lumps, weakness, bone pain, difficulty in moving and walking, and pathologic fractures. The biochemical analysis showed normal serum calcium levels (average = 9.5 mg/dL), with low serum phosphorus (average = 2.2 mg/dL) and raised serum fibroblast growth factor 23 (FGF23) levels, in all the cases, wherever available. On histopathology, all tumors showed cells arranged in a hemangiopericytomatous pattern, including oval to short spindle forms. Multinucleate giant cells were present in nine tumors, and characteristic "grungy calcifications" was observed in eight tumors. Prominent pseudo cystic spaces were seen in eight tumors. A significant number of mitotic figures and tumor necrosis were not seen in any tumor. In five cases where follow-up was available, there was complete resolution of symptoms post-resection with no recurrence or metastasis. All those patients were free of disease until the last follow-up.

CONCLUSION

This constitutes the first largest comprehensive study on these rare tumors from our country. PMTs can be diagnosed based on certain histopathological features and correlation with clinicoradiological and biochemical findings. These are invariably benign neoplasms. Patients are relieved of their debilitating symptoms after adequate surgical tumor resection. Therefore, their correct and timely diagnosis is crucial.

Phosphaturic mesenchymal tumor with de novo liver metastases: a case report and literature review

Phosphaturic mesenchymal tumors (PMTs) are rare tumors that can cause tumor-induced osteomalacia (TIO) through overproduction of FGF23, a peptide hormone that causes renal phosphate wasting and reduced osteoblastic activity. The diagnosis of PMTs can be difficult to make as the presenting symptoms are non-specific. Although PMT is a rare entity, most cases are benign in nature, not requiring further intervention after surgery, as resection is typically curative. Here, we present a unique case of malignant PMT with de novo liver metastasis in a female patient who presented with TIO and underwent surgical resection of her primary lesion with subsequent regression of her liver metastasis. Moreover, we analyze a review of literature and discuss the importance of a timely diagnosis of this rare phenomenon. It is encouraged that providers strongly consider a diagnosis of PMT in patients with otherwise unexplained bone pain, fatigue, weakness, especially if accompanied with hypophosphatemia. Further studies are also warranted to identify prognostic factors that predict a PMT's malignant potential as they may help identify possible therapeutic targets.

Prolonged generalized osteomalacia associated with a sinonasal cavity phosphaturic mesenchymal tumor: A case report

Phosphaturic mesenchymal tumor (PMT) is a rare disorder primarily affecting the extremities. It is notable for its correlation with hypophosphatemic osteomalacia and high FGF23 serum levels, which results in renal phosphate wasting and clinical symptoms associated with low serum phosphorus. We presented a patient with a 5-year history of progressive osteomalacia who recently experienced a major pathological bone fracture. Laboratory findings showed a persistent low serum phosphate, normal calcium, elevated alkaline phosphatase activity, high parathyroid hormone levels, and increased renal excretion of phosphate. According to ultrasonography and nuclear imaging, there was no evidence of parathyroid adenoma. During further diagnostic assessment, a sinonasal cavity tumor was found and resected. Histologically, the tumor was composed of bland spindle cell proliferation in the background of a calcified matrix with foci of osteoid formation, hemangiopericytoma-like (HPC-like) vasculature, and osteoclast-like giant cells. Tumor cells showed variable positivity for SMA, but CD34, S100, CD99, Melan-A, p63, and desmin were all nonreactive. Regarding the clinical context, histological and immunohistological findings, a final diagnosis of tumor-induced osteomalacia (TIO) secondary to a PMT was made. After surgery, laboratory results returned to normal, clinical symptoms disappeared, and the patient did not experience a recurrence during a six-month follow-up.

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.

Imaging characteristics of phosphaturic mesenchymal tumors

BACKGROUND

Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome associated with phosphaturic mesenchymal tumors (PMTs). Localization of the causative tumor in these cases is an arduous task since the culprit lesions are usually small, slow-growing, and can be located almost anywhere from head to toe.

PURPOSE

To describe the morphological characteristics of histologically proven PMTs on various radiological modalities.

MATERIAL AND METHODS

After institutional ethical approval, this retrospective study analyzed 20 cases with a histopathological evidence of PMT. Various imaging characteristics of the tumors on available computed tomography (CT) and magnetic resonance imaging (MRI) scans were evaluated. Descriptive statistical analyses were conducted.

RESULTS

The tumors were located in diverse locations: lower extremities (n = 10); head and neck (n = 5); vertebral column (n = 3); pelvis (n = 1); and upper extremities (n = 1). Bone lesions seen on CT had variable morphology: sclerotic (n = 3/8, 37.5%); lytic (n = 3/8, 37.5%), and both lytic and sclerotic (n = 2/8, 25%) with presence of narrow zone of transition in all cases (n = 8/8) and amorphous internal matrix calcifications in 25% of cases (n = 2/8). Of the tumors, 68.4% (n = 13/19) were hypointense on T1 and all of them showed hyperintense signal on T2-weighted and STIR images (n = 19/19) and contrast enhancement (n = 16/16). Of the tumors, 66.7% (n = 6/9) showed restricted diffusion. DOTANOC PET/CT showed tumor uptake in all cases (n = 8/8).

CONCLUSION

PMTs may have variable and non-specific tumor appearances on various imaging modalities. However, in an appropriate clinical scenario and a background of suggestive biochemical work-up, the radiologist should keep a high index of suspicion.

Case report: Novel NIPBL-BEND2 fusion gene identified in osteoblastoma-like phosphaturic mesenchymal tumor of the fibula

Phosphaturic mesenchymal tumor (PMT) is a rare tumor that secretes fibroblast growth factor 23 (FGF23) and causes hypophosphatemia and tumor-induced osteomalacia (TIO). Fusion genes FN1-FGFR1 and FN1-FGF1 have been detected in some PMTs, but the pathogenesis of PMTs without these fusion genes remains unclear. Here, we report a 12-year-old boy with persistent muscle weakness and gait disturbance. Roentgenographic examination revealed a radiolucent lesion with endosteal scalloping in the left fibula, while his serum level of FGF23 was markedly increased. Combined with simple X-ray findings of other body parts, we suspected that TIO was caused by PMT, and resected the tumor. After resection, the serum level of FGF23 started to decrease immediately and normalized within 3 hours after resection, with this being earlier than normalization of the serum phosphorus level. In RNA sequencing, FN1-FGFR1 and FN1-FGF1 were not detected, but a novel NIPBL-BEND2 fusion gene was identified. When we forcedly expressed this fusion gene in HEK293T cells and MG63 cells, cell proliferation was enhanced in both cell lines. Furthermore, Gene set enrichment analysis of HEK293T cells showed significant upregulation of MYC-target genes. Our results suggest that this novel NIPBL-BEND2 fusion gene promotes cell proliferation possibly via the MYC pathway and might be one of the etiologies of PMTs other than FN1-FGFR1 or FN1-FGF1.

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.

Tumor-induced osteomalacia treated with T12 tumor resection

Summary

Tumor-induced osteomalacia (TIO) is a rare form of osteomalacia caused by fibroblast growth factor-23 (FGF23)-secreting tumors. Most of these tumors are phosphaturic mesenchymal tumors (PMTs) typically involving soft tissue in the extremities and bone of the appendicular skeleton and cranium. We report the case of a 60-year-old woman with about 3 years of persistent bone pain and multiple fractures, initially diagnosed as osteoporosis, who was found to have hypophosphatemia with low 1,25-dihydroxyvitamin D and elevated alkaline phosphatase and inappropriately normal FGF23 consistent with TIO. Her symptoms improved with phosphate supplementation, vitamin D and calcitriol. 68Ga-DOTATATE imaging revealed a T12 vertebral body lesion confirmed on biopsy to be a PMT. She underwent resection of the PMT with resolution of TIO and increased bone density. This rare case of TIO secondary to a PMT of the thoracic spine highlights some of the common features of PMT-associated TIO and draws attention to PMT-associated TIO as a possible cause of unexplained persistent bone pain, a disease entity that often goes undiagnosed and untreated for years.

Learning points

Tumor-induced osteomalacia (TIO) is typically caused by phosphaturic mesenchymal tumors (PMTs) that are usually found in the soft tissue of the extremities and bone of the appendicular skeleton/cranium and rarely in the spine. TIO may be misdiagnosed as osteoporosis or spondyloarthritis, and the correct diagnosis is often delayed for years. However, osteoporosis, in the absence of fracture, is not associated with bone pain. The hallmark of TIO is hypophosphatemia with inappropriately normal or low 1,25-dihydroxyvitamin D and elevated or inappropriately normal fibroblast growth factor-23 (FGF23) levels. In patients with unexplained persistent bone pain, a serum phosphate should be measured. Consider PMT-associated TIO as a potential cause of unexplained persistent bone pain and hypophosphatemia. PMTs express somatostatin receptors and may be identified with 68Ga-DOTATATE imaging. Complete surgical resection is the preferred treatment for spinal PMTs associated with TIO.

Utility of Multimodality Approach Including Systemic FGF23 Venous Sampling in Localizing Phosphaturic Mesenchymal Tumors

Context

Tumor-induced osteomalacia (TIO) is one of the most common forms of acquired fibroblast growth factor 23 (FGF23)-related hypophosphatemia and is usually caused by phosphaturic mesenchymal tumors (PMTs). Although the complete resection of PMTs can cure TIO, preoperative localization of tumors by standard imaging modalities is often challenging. In addition to ¹⁸F-fluoro-2-deoxy-D-glucose positron emission tomography-computed tomography (FDG-PET) and ¹¹¹In-pentetreotide scintigraphy (SRS), systemic FGF23 venous sampling (FGF23VS) has been used to help localize PMTs in specialized institutions.

Objective

This study aimed to evaluate the diagnostic performance of each imaging test and their combinations in localizing PMTs.

Methods

In an observational retrospective study of patients with adult-onset FGF23-related osteomalacia who underwent all 3 imaging studies (FDG-PET, SRS, and FGF23VS), the rate of successful preoperative localization of the tumors was evaluated only in the patients with pathological diagnoses of PMTs, considering the possibility that pathogenesis of patients without identified tumors might be due to other causes such as late-onset hereditary FGF23-related hypophosphatemia.

Results

A total of 30 Japanese patients with TIO (median age, 60 years [range, 28-87 years]; 10 women [33.3%]) were included in the study. The success rate of preoperative localization for each test and combinations of 2 or 3 tests among 18 patients with PMTs was as follows: 72% (FDG-PET), 72% (SRS), 94% (FGF23VS), 89% (FDG-PET, SRS), 100% (FDG-PET, FGF23VS), 94% (SRS, FGF23VS), and 100% (FDG-PET, SRS, and FGF23VS).

Conclusion

We observed the highest localization rate of PMTs in patients with identified PMTs with the combination of FDG-PET and FGF23VS.

Tumour-induced osteomalacia due to a durally-based intracranial phosphaturic mesenchymal tumour

A man in his 40s was referred with persistent hypophosphataemia and bony pain. A serum fibroblast growth factor 23 level was markedly elevated and a diagnosis of tumour-induced osteomalacia was considered. Whole body imaging revealed multiple insufficiency fractures but no osseus tumours. There was, however, a durally-based intracranial lesion whose imaging characteristics were consistent with a meningioma. The tumour was removed, leading to rapid normalisation of the patient's symptoms and serum markers. Histology confirmed a phosphaturic mesenchymal tumour. We review the literature regarding this rare clinical situation.

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.

Phosphaturic Mesenchymal Tumor: An Unusual Cause of Stress Fractures Presenting to Sports Medicine

Phosphaturic mesenchymal tumors (PMT) are a rare neoplasm oftentimes associated with tumor-induced osteomalacia (TIO). The non-specific presentation and symptoms of these pathologies make them difficult to diagnose. We report a case of a 52-year-old patient with an intermetatarsal phosphaturic mesenchymal tumor who presented to the orthopedic sports medicine clinic with metabolic deficiencies and bilateral subtrochanteric cortical stress fractures indicative of osteomalacia. The tumor was entirely resected within nine months of symptom onset and has shown no recurrence at the one-year follow-up. This case report characterizes an unusual cause of stress fractures presenting to orthopedic sports medicine clinics and the variability in the presentation of phosphaturic mesenchymal tumors.

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 of the Ankle: A Case Report and Review of the Literature

We report the case of a phosphaturic mesenchymal tumor of the ankle; an extremely rare lesion that causes osteomalacia via paraneoplastic renal phosphate wasting. A 41-year-old man was referred to plastic surgery with a swelling over the anterior ankle, which had been increasing in size for 1 year. Focused ultrasound assessment was inconclusive, but excision biopsy demonstrated features in keeping with a phosphaturic mesenchymal tumor. Evidence of tumor-induced osteomalacia was subsequently identified on review of historical biochemistry. The patient was followed-up for 1 year with normalization of serum phosphate. In this case report, we present a discussion of the differential diagnosis for foot and ankle soft tissue lesions, and a review of the literature regarding the diagnosis and management of these tumors. Accurate identification of any soft tissue lesion on clinical examination alone is extremely challenging and excision biopsy should be considered in cases of diagnostic uncertainty.

FGF-23 transmitted tumor - induced hypophosphatemic osteomalacia: a rare case of a young woman with recurrent fractures and review of the literature

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Tumor-transmitted osteomalacia is a rare FGF 23 transmitted phosphaturic disease.

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Delay of diagnosis is common due to small and clinically silent underlying tumors.

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The most sensitive imaging modality is ⁶⁸Ga-DOTA-TOC-PET/CT-scan.

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Complete resection of the tumor mass cures this paraneoplastic disease.

We present a case of tumor-induced osteomalacia (TIO) in a young woman of 22 years. The fibroblast growth factor 23 transmitting tumor in her left foot remained undetected for several years. She suffered several fractures including insufficiency fractures of both femoral necks requiring bilateral proximal femoral nailing. After phosphaturia was diagnosed any known genetic etiology was excluded. Even advanced imaging modalities were unable to detect the clinically silent tumor until an ⁶⁸Ga-DOTA-TOC-PET/CT-scan revealed a mass with paraneoplastic activity in the left foot. Complete resection of the tumor proved to cure her condition after 9 years of uncertainty and suffering. Serum phosphate levels returned to normal within days.

After presentation of the case report, the current literature on published cases of TIO between 1956 and 2021 is summarized to emphasize the importance of an accurate and early diagnosis. Our case report aims to illustrate that a long latency period of diagnosis may be avoided utilizing the latest imaging techniques to spare affected patients from long treatment of symptoms instead of finding the underlying cause.

Surgical margin for phosphaturic mesenchymal tumors in soft tissues: An analysis of the radiological histopathological correlation

BACKGROUND

Phosphaturic mesenchymal tumors primarily cause tumor-induced osteomalacia, a rare paraneoplastic syndrome, and half occur in soft tissues. There are few reports about the surgical margins of these tumors. This study aimed to clarify the optimal surgical margin for phosphaturic mesenchymal tumors by analyzing radiological and histopathological features.

METHODS

This study included eight cases, seven primary and one recurrent, of tumor-induced osteomalacia caused by soft-tissue phosphaturic mesenchymal tumors that were surgically treated between January 2000 and January 2019. We evaluated the radiological and histopathological features of all tumors and investigated the correlation of these features, the surgical margin, and recurrence of hypophosphatemia.

RESULTS

The tumors were located in superficial (n = 5) and deep (n = 3) tissues. Six of the eight tumors had a clear boundary, but five had an irregular margin. Three tumors had a hypointense rim on T2-weighted images, indicating fibrous tumor encapsulation. Histopathological analysis revealed infiltrative growth in six of the eight tumors, which correlated with an irregular margin seen on imaging. Although there was no recurrence in patients treated with an intended wide margin >1 cm, one of the three patients treated with marginal tumor resection experienced a recurrence of hypophosphatemia, with histopathological analysis showing infiltration of subcutaneous fat. In contrast, two tumors with clear boundaries, regular margins, and fibrous capsule seen on imaging, had no infiltrative growth and were cured by marginal resection. In one recurrent case, tumor infiltration was observed in the previous surgical scar, which was not detected on preoperative imaging.

CONCLUSIONS

Soft-tissue phosphaturic mesenchymal tumors with an irregular boundary seen on imaging tend to be infiltrative, especially into subcutaneous fat, and should be treated by at least a 1-cm wide margin resection. Tumors with a fibrous capsule with clear and regular margins are cured by marginal margin resection. These findings could inform surgeons' decisions regarding the resection of soft-tissue phosphaturic mesenchymal tumors.

The phosphaturic mesenchymal tumor as a cause of oncogenic osteomalacia. Three cases and review of the literature

INTRODUCTION

The phosphaturic mesenchymal tumour (PMT) is a very uncommon cause of oncogenic osteomalacia (OO), which is a paraneoplastic syndrome with severe clinical osteomalacia. The PMT is a neoplasia that produces the fibroblast growth factor FGF23, resulting in reduced proximal tubular phosphate reabsorption leading to hyperphosphaturia and hypophosphatemia. Our aim is to present our experience and complications in diagnosis and treatment of PMT in three patients.

MATERIAL AND METHODS

We propose an observational, descriptive and retrospective study of three cases of OO secondary to PMT found in our database of bone and soft tissue tumours. The inclusion criteria were: symptoms related with OO, presence of hyperphosphaturic hypophosphatemia, elevated levels of FGF23 in blood and pathological diagnosis of PMT.

RESULTS

In all cases, the disease showed asthenia, non-specific bone pain, progressive functional weakness, and pathological fractures. The average delay time in diagnosis was 7 years. All presented with hyperphosphaturic hypophosphatemia, elevated levels of alkaline phosphatase as well as FGF23. The use of Octreoscan and PET-CT were essential to find the producing tumour and its subsequent biopsy. Treatment was surgery in two cases and one case was treated by CT-guided cryotherapy with neurophysiological control. Once the surgery was performed, the blood parameters normalized. There is no recurrence.

CONCLUSIONS

Phosphaturic mesenchymal tumor is a very rare entity as part of bone and soft tissue tumors, it may occur in both tissues. The phosphate-calcium homeostasis is altered due to high serum levels of FGF23 because of PMT. Delay in diagnosis is usual, leading to renal and skeletal comorbidities. To avoid this, knowledge of this entity together with high diagnostic suspicion are critical. Surgical treatment leads to normalization of serum levels and systemic symptoms.

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.

Oncogenic osteomalacia due to phosphaturic mesenchymal tumour in the upper thoracic spine

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 (68Ga 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.

Lessons learnt from delayed diagnosis of FGF-23-producing tumour-induced osteomalacia and post-operative hungry bone syndrome

Tumour-induced osteomalacia (TIO) is a rare paraneoplastic syndrome caused by a fibroblast growth-factor-23 (FGF-23)-secreting phosphaturic mesenchymal tumour (PMT) and is characterised by hypophosphataemic osteomalacia. We present a 36-year-old man initially presenting with diffuse bone and joint pain who was inappropriately treated for presumed ankylosing spondylitis for 2 years. Whole-body bone scan suggested metabolic bone disease, prompting referral to our endocrine institution. He was subsequently diagnosed with persistent hypophosphataemia, inappropriately high renal tubular phosphate excretion, 1,25-dihydroxyvitamin D₃ suppression, severe osteoporosis and severe osteomalacia. FGF-23 concentrations (140 ng/L) were raised 3-fold above the upper limit of normal. Initial Gallium-68 (⁶⁸Ga) DOTATATE positron emission tomography (PET)/CT scan missed an active lesion in the left fibular head as the field only included the mid-brain to the proximal femora. Histopathology results from tumour resection confirmed a PMT over-expressing FGF-23. Serum phosphate and FGF-23 normalised immediately post-operatively. He developed severe hypocalcaemia 3-weeks post-operatively (1.77 mmol/L) which normalised after 1 month of high-dose caltrate and calcitriol therapy. Osteomalacia, osteoporosis and associated symptoms resolved during medium-term follow-up with >100% improvement in his bone mineral density. This case report and discussion highlights the pitfalls contributing to delayed diagnosis of TIO and alerts clinicians to the potential complication of hungry bone syndrome post-tumour resection.

Phosphaturic Mesenchymal Tumors from Head to Toe: Imaging Findings and Role of the Radiologist in Diagnosing Tumor-Induced Osteomalacia

BACKGROUND

This study aimed at evaluating the imaging findings of phosphaturic mesenchymal tumors and tumor-induced osteomalacia and assess the clinical and biochemical profiles of patients with tumor-induced osteomalacia.

MATERIALS AND METHODS

Imaging findings in six patients with tumor-induced osteomalacia and histopathologically proven phosphaturic mesenchymal tumors were evaluated. Clinical and biochemical profiles of these patients were also assessed.

RESULTS

Along with having a characteristic biochemical profile, patients with phosphaturic mesenchymal tumors also have certain imaging findings which can aid in the diagnosis such as increased uptake on DOTA PET-CT and homogeneous post-contrast enhancement on CT and MRI.

CONCLUSION

Patients with tumor-induced osteomalacia have characteristic symptoms, imaging and biochemical profiles. For radiologists, raising the suspicion of a phosphaturic mesenchymal tumor in patients with refractory hypophosphatemic osteomalacia as well as localizing the tumor on imaging is crucial, as complete excision of the tumor leads to resolution of the osteomalacia and the patient's clinical symptoms.

Phosphaturic Mesenchymal Tumor of Soft Tissue of the Foot: Report of a Case With Review of the Literature

Phosphaturic mesenchymal tumor (PMT) is a rare neoplasm that ectopically secretes fibroblast growth factor 23, a bone cell-derived protein that regulates phosphate homeostasis. The overproduction of fibroblast growth factor 23 causes a paraneoplastic syndrome characterized by hyperphosphaturia, hypophosphatemia, hypovitaminosis D, and vitamin D refractory rickets/osteomalacia, effects that disappear with tumor removal. The PMT may occur in several anatomic regions, mainly in the limbs, usually involving both soft tissue and bone. Acral locations occur in 10% to 15% of the cases, mostly in the feet, with 95 cases reported in this anatomic region to date. We report a case of a PMT in a young adult male who presented in 2007 with the classic constellation of signs and symptoms. A small soft-tissue tumor was detected in his right heel, 3 years after exhaustively seeking for it by various imaging techniques performed at different institutions. Before the tumor was detected, attempts to manage this patient's osteomalacia with phosphate and vitamin D (both calcitriol and ergocalciferol) supplementation were unsuccessful. Following surgical resection, the patient experienced prompt correction of the phosphaturia and gradual reconstitution of his bone mineralization. The pathologic diagnosis was (benign) PMT, mixed connective tissue type. In 2019, 12 years after resection, the patient is asymptomatic, and his bone mineral homeostasis has been restored.

Phosphaturic mesenchymal tumors among elderly patients: a case report and review of literature

Phosphaturic mesenchymal tumor (PMT) represents a rare cause of osteomalacia. The clinical signs and symptoms are vague and these lead to diagnosis delay. In the presence of hypophosphatemia and relatively high urine phosphate excretion, this entity should be taken into consideration in the deferential diagnosis of osteomalacia. In the present article, we report 81-year-old man presented to our clinic for evaluation due to osteopenia. His laboratory results disclosed hypophosphatemia, relatively increased urine phosphate excretion and increased level of intact fibroblast growth factor 23 (FGF23). A 68Gallium DOTATATE PET/CT revealed pathological uptake in the upper aspect of the left shoulder adjacent to the coracoid process. For suspected PMT a wide resection of the tumor was performed and pathological findings were consistent for PMT. Laboratory tests were normalized postoperatively. Reviewing the literature, we had identified 33 reported cases of PMTs among elderly patients age ≥70 years. Unlike previously reported data, where tumors predominantly localized in the lower extremities and pelvis, our search disclosed a high rate of tumor localization (10 cases - 33.3%) in the head with equal number of tumors (14 cases - 42.4%) localized in the head and upper extremity as well as in pelvis and lower extremity. The present case describes unique tumor localization in an elderly patient and our literature search demonstrated for the first time a high rate of tumor localization in the head among this group of patients. Learning points: PMTs represent a rare entity that should be considered in the differential diagnosis of elderly patients presented with persistent hypophosphatemia. Unlike previously reported data, head and neck tumor localization is frequent among elderly patients. 68Gallium-conjugated somatostatin peptide analogs, such as 68Ga-DOTATATE PET/CT demonstrated the greatest sensitivity and specificity for tumor localization in patients with phosphaturic mesenchymal tumors (PMTs). Wide tumor resection using intraoperative ultrasound is of major importance in order to ensure long-term cure.

Tumor-induced osteomalacia

Tumor-induced osteomalacia (TIO), also known as oncogenic osteomalacia, is a rare paraneoplastic syndrome characterized by hypophosphatemia resulting from decreased tubular phosphate reabsorption, with a low or inappropriately normal level of active vitamin D. The culprit tumors of TIO could produce fibroblast growth factor 23 which plays a role in regulating renal Pi handling and 25-hydroxyvitamin D 1α-hydroxylase activity. Chronic hypophosphatemia could eventually lead to inadequate bone mineralization, presenting as osteomalacia. The diagnosis should be considered when patients manifest as hypophosphatemia and osteomalacia, or rickets and needs to be differentiated from other disorders of phosphate metabolism, such as the inhereditary diseases like X-linked hypophosphataemic rickets, autosomal dominant hypophosphataemic rickets, autosomal recessive hypophosphataemic rickets and acquired diseases like vitamin D deficiency. Localization of responsible tumors could be rather difficult since the vast majority are very small and could be everywhere in the body. A combination of thorough physical examination, laboratory tests and imaging techniques should be applied and sometimes a venous sampling may come into handy. The technology of somatostatin-receptor functional scintigraphy markedly facilitates the localization of TIO tumor. Patients undergoing complete removal of the causative neoplasm generally have favorable prognoses while a few have been reported to suffer from recurrence and metastasis. For those undetectable or unresectable cases, phosphate supplements and active vitamin D should be administrated and curative intended radiotherapy or ablation is optional.

Diagnostic performance and impact on patient management of 68Ga-DOTA-TOC PET/CT for detecting osteomalacia-associated tumours

PURPOSE

Oncogenic osteomalacia is an endocrine disorder induced by small benign tumours (TIO) producing excessive fibroblast growth factor-23 (FGF23). The only way of curing oncogenic osteomalacia is surgical resection of the culprit TIO, which is extremely difficult to detect using conventional imaging modalities due to its small size and variable location in the body. Since TIO frequently overexpress somatostatin receptors, a clinical utility of SPECT or PET with radiolabelled somatostatin analogues has been reported. Among them, ⁶⁸Ga-DOTA-TOC has recently been granted a marketing authorization, facilitating its routine application. We report here the results of the first series evaluating the diagnostic performance of ⁶⁸Ga-DOTA-TOC PET/CT in detecting TIO and its impact on patient management.

METHODS

⁶⁸Ga-DOTA-TOC PET/CT and clinical and imaging data from 15 patients with clinical and biochemical signs of oncogenic osteomalacia were retrospectively reviewed. The ⁶⁸Ga-DOTA-TOC PET/CT findings were compared with the results of post-surgical pathology and clinical and biochemical follow-up.

RESULTS

⁶⁸Ga-DOTA-TOC PET/CT resulted in the detection of one focus suspicious for TIO in nine of 15 patients (60%), and a tumour was surgically removed in eight. Post-operative pathology confirmed a TIO in those eight patients whose symptoms diminished promptly and biochemical anomalies resolved. ⁶⁸Ga-DOTA-TOC PET/CT sensitivity, specificity and accuracy were 73%, 67% and 71%, respectively. ⁶⁸Ga-DOTA-TOC PET/CT findings affected patient management in 67% of cases. In particular, ⁶⁸Ga-DOTA-TOC PET/CT was able to detect the TIO with a negative or a false-positive result of a previous ¹¹¹In-pentetreotide SPECT/CT in 5/8 patients (63%) or a previous FDG PET/CT in 7/11 patients (64%). No close relationship was found between the positivity of ⁶⁸Ga-DOTA-TOC PET/CT and the serum level of a biochemical marker. However, a true-positive result of ⁶⁸Ga-DOTA-TOC PET/CT was obtained in only one patient with a non-elevated serum level of FGF23.

CONCLUSION

⁶⁸Ga-DOTA-TOC PET/CT is an accurate imaging modality in the detection of TIO; in particular, it is worthwhile after failure of somatostatin receptor SPECT(/CT) or FDG PET/CT.

The Findings on Bone Scintigraphy in Patients With Suspected Tumor-Induced Osteomalacia Should Not Be Overlooked

Tumor-induced osteomalacia (TIO) is a chronic, devastating disease. The causative tumor is usually a small benign one that is very difficult to localize. Because the presenting symptoms include diffuse bone pain, a bone scintigraphy is commonly performed to determine the cause of the pain before TIO is suspected. In this retrospective investigation, we tried to assess whether bone scintigraphy acquired will be helpful in the eventual identification of the culprit tumor.

METHODS

The images of bone scan and clinical charts of total 91 patients with confirmed TIO were retrospectively reviewed. The image findings were compared with the results of other imaging studies, surgical notes, histopathologic examinations and clinical follow-ups.

RESULTS

In 76.9% (70 of 91) of the patients, the findings of bone scintigraphy did not correspond to the sites of the causative tumors, which were subsequently located. However, in 23.1% of the patients (21 of 91), the sites of the causative tumors corresponded to one of the abnormal technetium 99m-methyl diphosphonate activity on bone scintigraphy. More importantly, 6 tumors corresponded to the dominant activity on bone scintigraphy.

CONCLUSIONS

Although findings of whole-body scintigraphy are nonspecific in patients with TIO, careful evaluation of bone scintigraphy results can be helpful in guiding further evaluation in some patients.

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 Tumors: Clinicopathologic, Immunohistochemical and Molecular Analysis of 22 Cases Expanding their Morphologic and Immunophenotypic Spectrum

Phosphaturic mesenchymal tumor (PMT) is a rare neoplasm of uncertain histogenesis that has been linked to tumor-induced osteomalacia (TIO) since 1959. The neoplastic cells produce increased amount of FGF23 which results in TIO via uncontrolled renal loss of phosphate (phosphaturia), and consequently diminished bone mineralization. To date, ∼300 cases have been reported. Although there is increasing evidence that PMT can be diagnosed by reproducible histopathologic features, firm diagnosis has been often restricted to cases associated with TIO and, hence, diagnosis of "nonphosphaturic variants" remained challenging. Recently, FGFR1/FN1 gene fusions were detected in roughly half of cases. We herein reviewed the clinicopathologic features of 22 PMTs (15 cases not published before), stained them with an extended immunohistochemical marker panel and examined them by fluorescence in situ hybridization for FGFR1 gene fusions. Patients were 12 males and 9 females (one of unknown sex) aged 33 to 83 years (median: 52 y). Lesions affected the soft tissues (n=11), bones (n=6), sinonasal tract (n=4), and unspecified site (n=1). Most lesions originated in the extremities (9 in the lower and 4 in the upper extremities). Acral sites were involved in 10 patients (6 foot/heel, 3 fingers/hands, and 1 in unspecified digit). Phosphaturia and TIO were recorded in 10/11 and 9/14 patients with detailed clinical data, respectively. Limited follow-up (5 mo to 14 y; median: 16 mo) was available for 14 patients. Local recurrence was noted in one patient and metastasis in another patient. Histologically, 11 tumors were purely of conventional mixed connective tissue type, 3 were chondromyxoid fibroma-like, 2 were hemangio-/glomangiopericytoma-like with giant cells, and 1 case each angiomyolipoma-like and reparative giant cell granuloma-like. Four tumors contained admixture of patterns (predominantly cellular with variable conventional component). Immunohistochemistry showed consistent expression of CD56 (11/11; 100%), ERG (19/21; 90%), SATB2 (19/21; 90%), and somatostatin receptor 2A (15/19; 79%), while other markers tested negative: DOG1 (0/17), beta-catenin (0/14), S100 protein (0/14), and STAT6 (0/7). FGFR1 fluorescence in situ hybridization was positive in 8/17 (47%) evaluable cases. These results add to the phenotypic delineation of PMT reporting for the first time consistent expression of SATB2 and excluding any phenotypic overlap with solitary fibrous tumor or sinonasal glomangiopericytoma. The unifying immunophenotype of the neoplastic cells irrespective of the histologic pattern suggests a specific disease entity with diverse morphotypes/variants rather than different neoplasms unified by TIO.

Treatment and outcomes of tumor-induced osteomalacia associated with phosphaturic mesenchymal tumors: retrospective review of 12 patients

Background

Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome characterized by severe hypophosphatemia and osteomalacia. Nonspecific symptoms make the diagnosis elusive. In addition, locating the responsible tumor(s) is challenging. The aim of this study was to investigate the clinical management and outcomes of TIO.

Methods

The clinical features, diagnostic procedures, treatment, and outcomes of 12 patients were reviewed retrospectively.

Results

The cohort comprised six men and six women (mean age 45.5 ± 9.9 years, range 23–61 years). The mean duration of disease was 3.7 ± 2.6 years. All patients manifested progressive bone pain, muscle weakness, and/or difficulty walking. Serum phosphorus concentrations were low in all patients (mean 0.42 ± 0.12 mmol/L). Technetium-99m octreotide scintigraphy was performed in 11 patients and showed lesions in the right distal femur, left femoral head, and right tibial plateau, respectively, in three patients. Magnetic resonance imaging (MRI) was negative for lesions in one patient. Two patients underwent biopsies that showed negative histopathology. Two patients, at 2 years and 8 months, respectively, after having negative technetium-99m octreotide studies, underwent ¹⁸F–fluorodeoxyglucose positron emission tomography/computed tomography (CT), which revealed lesions in the sacrum and soft tissue of the left palm, respectively. One tumor was detected by CT and MRI. Overall, lesion sites were the head (two patients, 16.7%), thoracic and lumbar region (two, 16.7%), pelvis (three, 25%), lower limbs (four, 33.3%), and upper limbs (one, 8.3%). All patients underwent surgery, and histopathology showed phosphaturic mesenchymal tumors in each. Postoperatively, serum phosphorus concentrations normalized within 2–7 days in 11 patients. With follow-ups of 1–41 months, surgery was effective in 10 patients. One patient developed local recurrence and another had metastases.

Conclusions

Locating tumors responsible for tumor-induced osteomalacia is often challenging. Although complete tumor resection confers a good prognosis in most patients, surveillance for recurrence and metastasis is necessary. Before surgery or when surgery is not indicated, oral phosphate can alleviate symptoms and metabolic imbalance.

Electronic supplementary material

The online version of this article (10.1186/s12891-017-1756-1) contains supplementary material, which is available to authorized users.

The diagnostic dilemma of tumor induced osteomalacia: a retrospective analysis of 144 cases

Diagnostic delay of tumor induced osteomalacia (TIO) is common in clinic practice. To investigate the diagnostic condition of TIO in China and raise clinicians' awareness of TIO, we retrospectively analyzed clinical manifestations, biochemical features, and specially evaluated missed diagnoses and misdiagnoses among 144 TIO patients from Peking Union Medical College Hospital during December 1982 to December 2014. Clinical presentations of TIO mainly included bone pain, difficulty in walking, pathological fractures, muscle weakness, and height loss. TIO patients demonstrated hypophosphatemia (0.48±0.13 mmol/L), elevated serum alkaline phosphatase (277.9±152.6 U/L), reduced tubular maximum for phosphorus/glomerular filtration rate (0.39±0.14) and markedly elevated serum fibroblast growth factor 23 (FGF23) (median level 302.9 pg/mL). The average time from onset to a correct diagnosis was 2.9±2.3 years while the mean duration from onset to tumor resection was 5.4±4.2 years. The initial misdiagnosis rate was 95.1% (137/144) and 240 case-times of misdiagnoses occurred among the 144 cases. The most frequent misdiagnoses were intervertebral disc herniation, spondyloarthritis (including ankylosing spondylitis) and osteoporosis. A total of 43.1% (62/144) cases with hypophosphatemia presented on their laboratory sheets were neglected and missed diagnosed. Our study showed that TIO was frequently misdiagnosed and missed diagnosed due to its rarity, insidious onset, nonspecific clinical manifestations and clinicians' poor recognition. It is necessary to test serum phosphorus in patients with musculoskeletal symptoms and difficulty in walking. The measurement of serum FGF23 is rather valuable. Once hypophosphatemia is discovered, TIO should be suspected and it is highly recommended to search for tumors and perform curative surgery.

Phosphaturic mesenchymal tumor of the nasal cavity and paranasal sinuses: A clinical curiosity presenting a diagnostic challenge

Phosphaturic mesenchymal tumor (PMT) is a rare mesenchymal neoplasm associated with tumor-induced osteomalacia (TIO) and elevated serum FGF-23. Common in extremities, PMT rarely occurs in sinonasal region. We report a series of sinonasal PMT diagnosed at our institute over a 6-year period. Six cases of sinonasal PMT were identified during this period, of which five presented with features of TIO. Median age of patients was 45.5 years. All six tumors were composed of stellate to spindled cells, with prominent staghorn vasculature in four cases. Typical smudgy matrix was seen in all cases, but only focally; grungy calcification was absent. Accurate diagnosis of PMTs is imperative, as complete excision leads to dramatic resolution of TIO symptoms. Lack of knowledge of this entity prevents clinicians from ordering relevant investigations. Absence of specific morphological features, like grungy calcification, and presentation at atypical locations makes the diagnosis challenging. Awareness of this entity is essential in order to suspect PMT in patients presenting with a soft tissue mass and features of TIO, however unusual the location may be.

Oncogenic Osteomalacia Secondary to a Metastatic Phosphaturic Mesenchymal Tumor in the Talus: A Case Report and Review of the Literature

CASE

We report the case of a 50-year-old woman with oncogenic osteomalacia secondary to a metastatic phosphaturic mesenchymal tumor (PMT) that presented, to our knowledge, with the first reported lesion in the talus.

CONCLUSION

Oncogenic osteomalacia is a rare condition with a unique serum biochemical profile that requires a high index of suspicion for diagnosis. A PMT is a rare neoplasm that can lead to oncogenic osteomalacia through secretion of fibroblast growth factor 23. Symptoms can be debilitating, and diagnostic delays are extremely common. This case report emphasizes the importance of comprehensive anatomic assessment and the need for fastidious postoperative monitoring.