Surgical Treatments of Tumor-Induced Osteomalacia Lesions in Long Bones: Seventeen Cases with More Than One Year of Follow-up

Long-Term Follow-Up Data of Tumor-Induced Osteomalacia Managed with Surgery and/or Radiofrequency Ablation from a Single Center

Data on radiofrequency ablation (RFA) in tumor-induced osteomalacia (TIO) are restricted to case reports (~ 11 patients) and long-term follow-up data are further scarce. We describe our experience on managing TIO from a tertiary care center in India. Retrospective study of patients with localized TIO was performed and clinical, biochemical, treatment and follow-up details were retrieved. Normalization of serum phosphorus in absence of phosphate supplementation was defined as remission. Of 33 patients (23 males), 24 patients underwent surgery as first-line treatment, and early remission, delayed remission (> 1 month for phosphorus normalization) and persistence were observed 12, 3, and 9 patients at a median follow-up of 5 (4-9) years. The gender, age, tumor size, location of tumors and FGF23 levels were not statistically different in patients who were in remission after surgery versus those with persistent disease. Second/third line treatment included conventional medical treatment and/or repeat surgery (n = 3), radiotherapy (n = 3), peptide receptor radionuclide therapy (n = 1), RFA (n = 1). Two patients had transient worsening (weeks) of weakness post-surgery. 10 patients underwent RFA (first-line n = 9); at the last follow-up 5 (4-10) years, 7 are in remission. Two of three persistent disease patients had large tumors (5.6 and 3.6 cm). There were no RFA-related complications except local ulcer in one. Although persistent disease was present in a few patients in both arms, there was no recurrence in either RFA or surgical cohort. RFA provide durable response similar to surgery, persistence requires multi-modality treatment.

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.

Orthopedic Surgical Treatment of Patients with Tumor-induced Osteomalacia Located in the Hip Bones: A Retrospective Analysis of 10 Years in a Single Center

OBJECTIVE

The orthopedic surgical treatment strategies for patients with tumor-induced osteomalacia (TIO) require improvement, especially for patients where the causative tumors are located in surgically challenging areas, requiring a greater degree of in-depth investigation. This work aims to summarize and investigate clinical features and orthopedic surgical treatment effects of patients with tumor-induced osteomalacia (TIO), whose causative tumors are located in the hip bones.

METHODS

A retrospective analysis was conducted on the clinical data of all patients diagnosed with culprit tumors located in the hip bones who underwent surgical treatment at the orthopedic bone and soft tissue tumor sub-professional group of Peking Union Medical College Hospital from January 2013 to January 2023. This retrospective study summarized the clinical data, preoperative laboratory test results, imaging findings, surgery-related data, perioperative changes in blood phosphorus levels, and postoperative follow-up data of all patients who met the inclusion criteria. Normally distributed data are presented as mean and standard deviation, while non-normally distributed data are shown as the means and 25th and 75th interquartile ranges.

RESULTS

The clinical diagnostic criteria for TIO were met by all 16 patients, as confirmed by pathology after surgery. Among the 16 patients, we obtained varying degrees of bone pain and limited mobility (16/16), often accompanied by difficulties in sitting up, walking, and fatigue. An estimated 62.5% (10/16) of patients had significantly shorter heights during the disease stages. All 16 patients underwent surgical treatment for tumors in the hip bones, totaling 21 surgeries. In the pathogenic tumor, there were 16 cases of skeletal involvement and none of pure soft tissue involvement. Out of the 16 patients, 13 cases had a gradual increase in blood phosphorus levels following the latest orthopedic surgery, which was followed up for 12 months to 10 years. Due to unresolved conditions after the original surgery, four patients received reoperation intervention. Two cases of refractory TIO did not improve in their disease course.

CONCLUSION

In summary, the location of the causative tumor in the hip bone is hidden and diverse, and there is no defined orthopedic surgical intervention method for this case in clinical practice. For patients with TIO where the tumors are located in the hip bones, surgical treatment is difficult and the risk of postoperative recurrence is high. Careful identification of the tumor edge using precise preoperative positioning and qualitative diagnosis is crucial to ensure adequate boundaries for surgical resection to reduce the likelihood of disease recurrence and improve prognosis.

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.

Preoperative evaluation and orthopedic surgical strategies for tumor-induced osteomalacia

Tumor-induced osteomalacia (TIO), also known as oncogenic osteomalacia, is very rare, with about 1000 reported cases globally. Removing most TIO culprit tumors requires the evaluation and intervention of orthopedic doctors. However, orthopedic doctors often have a poor understanding of the optical treatment of TIO due to its rarity. In addition, most TIO patients lack specific clinical manifestations. Also, the clinical localization and qualitative diagnosis of TIO are difficult and thus can easily be misdiagnosed and mistreated. Furthermore, the true incidence rate of TIO may be underestimated. Although many breakthroughs have been made in exploring the pathogenesis, clinical diagnosis, and treatment of TIO, rational and standardized orthopedic surgical treatment experience summary and sorting for TIO patients are lacking. In this article, the recent experience and progress in the field of orthopedic surgical treatment for TIO globally have been summarized, providing a theoretical basis and new clinical practice guidance for the rational treatment of TIO patients.

[Clinical features, diagnostics and treatment of FGF23 secreting tumors: series of 40 clinical cases]

INTRODUCTION

Tumor-induced osteomalacia is an acquired rare disease manifested by hypophosphatemic osteomalacia due to excessive secretion of fibroblast growth factor 23 (FGF23). FGF 23 is a non-classical hormone secreted by bone tissue (osteocytes) and regulates phosphorus metabolism.The aim of this work is to present clinical experience in the diagnosis, treatment and rehabilitation of patients with tumor-induced osteomalacia.

MATERIALS AND METHODS

40 patients with clinically-confirmed tumor-induced osteomalacia were included in the study, 34 of whom had the tumor localized, 27 underwent surgical treatment and 21 achieved stable remission.

RESULTS

The median age was 48 [41; 63] years, 43% were men, the time left from the the onset of the disease was 8 [4; 10] years. Biochemical findings were hypophosphatemia 0.47 [0.4; 0.53] mmol/l, a decrease in the tubular reabsorption phosphate 62 [52; 67]%, and an increase in alkaline phosphatase of 183 [112; 294] units/l. At the time of diagnosis, 100% had multiple pathological fractures, only 10% could move independently, and 77.5% classified the pain as unbearable (8-10 points according to the 10-point pain syndrome scale ). Among the methods used to detect tumors, the most sensitive were scintigraphy with tectrotide with SPECT/CT 71.4% (20/28) and MRI 90% (18/20). In 35% of cases, the tumor was localized in soft tissues and in 65% in bone tissue; The tumor was most often detected in the lower extremities, followed by the head in frequency of localization. 18 patients currently have no remission and they receive conservative treatment (phosphorus and alfacalcidol n=15 and burosumab n=3). In case of achieving remission (n=21), regression of clinical symptoms and restoration of bone and muscle mass was observed. Extensive excision of the tumor without prior biopsy resulted in the best percentage of remission - 87%.

CONCLUSION

Tumor-induced osteomalacia is characterized by severe damage to bone and muscle tissue with the development of multiple fractures, muscle weakness and severe pain syndrome. In laboratory diagnostics, attention should be paid to hypophosphatemia, a decrease in the tubular reabsorption phosphate index and increased alkaline phosphatase. The use of functional diagnostic methods with a labeled somatostatin analogue to the subtype 2 receptor and MRI with contrast enhancement are the most accurate methods of topical diagnostics. In case of localization of the tumor, a wide excision without a preliminary biopsy is recommended.

Hemiarthroplasty for tumor-induced osteomalacia caused by tumor localized in femoral head: a case report

Tumor-induced osteomalacia (TIO) is a rare tumor-associated syndrome in which osteomalacia is induced by a tumor. A 67-year-old male patient presented for the first time with low back pain, weakness of the lower extremities and difficulty in walking. Six years earlier, he had nonspecific symptoms such as low back pain, and blood tests showed high alkaline phosphatase and low phosphorus. In addition, fibroblast growth factor 23 (FGF23) was abnormally high at 454 pg/mL. A diagnosis of FGF23-related hypophosphatemic osteomalacia was made. Somatostatin receptor scintigraphy, venous sampling and MRI were performed to localize and diagnose TIO. The tumor was found to be confined to the right femoral head and hemiarthroplasty was performed. Pathological examination revealed a phosphaturic mesenchymal tumor. Postoperatively, symptoms and blood test data improved. Although resection of the lesion and osteochondral transplantation or total hip arthroplasty were considered, hemiarthroplasty was chosen over concerns about treatment failure due to seeding.

[FGF23 tumor induced osteomalacia]

Tumor induced osteomalacia is a rare acquired disease. The cause is a mesenchymal tumor secreting fibroblast growth factor 23 (FGF23). An excessive amount of FGF 23 disrupts the metabolism of phosphorus and vitamin D, which leads to severe paraneoplastic syndrome, manifested in the form of multiple fractures, severe pain in the bones and generalized myopathy. With oncogenic osteomalacia, a complete cure is possible with radical resection of the tumor. Unfortunately, localization, small size of formations and rare frequency of occurrence lead to the fact that the disease remains unrecognized for a long time and leads to severe, disabling consequences. A step-by-step approach to diagnosis improves treatment outcomes. First, a thorough anamnesis is collected, then functional visualization is performed and the diagnosis is confirmed by anatomical visualization of the tumor. After that, the method of choice is a surgical treatment. If resection is not possible, then conservative therapy with active metabolites of vitamin D and phosphorus salts is indicated. New therapeutic approaches, such as the antibody to FGF23 or the pan-inhibitor of receptors to FGF, are actively developing. This article provides an overview of modern approaches to the diagnosis and treatment of this disease.

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.

Tumor induced osteomalacia: A single center experience on 17 patients

Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome due to a phosphaturic tumor, which overproduces Fibroblast Growth Factor 23 (FGF-23), causing hyperphosphaturia, hypophosphatemia, low 1,25(OH)₂D and osteomalacia. Tumor localization is critical, diagnostic delay ranges from 2.5 to 28 years and to date surgical removal is considered effective treatment. We retrospectively evaluated patients with definite diagnosis of TIO referred to a tertiary Rheumatology Center between September 2000 and May 2020, investigating clinical management and disease outcome. We included 17 patients: 10 (58.8%) were females, mean age at diagnosis was 55.3 ± 13.9 years (mean ± standard deviation), with a diagnostic delay from symptoms onset to tumor detection of 6.6 ± 6.25 years. Biochemical data were: serum phosphorus 1.3 ± 0.4 mg/dL (Reference Range: 2.5-4.6), serum 1,25(OH)₂D 31.8 ± 22.9 ng/mL (RR: 25-86), intact FGF-23, 358.9 ± 677 pg/mL (RR: 25-45); 24 h-Urine Phosphorus was increased in only 2 patients, while tubular reabsorption of phosphate (TRP) was decreased in all patients confirming a renal phosphate wasting. In 2013 ⁶⁸Ga- DOTA-based PET/CT was introduced in routinely practice and diagnostic delay was consistently reduced (from 8.6 ± 7.9 to 4.3 ± 2.4 years). Thirteen patients underwent surgery, one patient underwent radiofrequency ablation; 3 patients, not eligible for surgery, were treated only with supplements of phosphorus and calcitriol. One was started on Burosumab after several unsuccessful surgical attempts. After surgery or ablation, 8 patients had complete remission, 3 TIO persistence, and 3 had overtime relapse. Relapses were observed only in patients who previously underwent closed biopsy. To our knowledge, this is the widest European cohort of TIO patients in the last two decades. We confirm a usual diagnostic delay and recommend a stepwise diagnostic approach. Tumor biopsy is not recommended due to the potential cell spilling. Surgery is generally considered a definitive treatment, even though other approaches have been successful in curing TIO. Active surveillance on possible recurrence is always needed. Burosumab appears a promising therapy.

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.

Tumor-Induced Osteomalacia Caused by a Phosphaturic Mesenchymal Tumor of the Sole Presenting as a Crippling Illness in a Postmenopausal Woman

Tumor-induced osteomalacia, a rare and intriguing paraneoplastic syndrome that is usually caused by a phosphaturic mesenchymal tumor, leads to severe pain and hypophosphatemia. However, during clinical practice, most patients suffer from significant delay of diagnosis and treatment because the symptoms are similar to those of some very common diseases, such as osteoporosis and osteoarthritis. Moreover, physical complaints from postmenopausal women usually exacerbate the possibility of such delays. We describe a case of a postmenopausal woman with crippling bone pain and weakness, who had been diagnosed with a case of simple osteoporosis and osteoarthritis for 3 years, even with fine-needle aspiration biopsy of the offending phosphaturic mesenchymal tumor. After surgical removal of the 2 × 3-cm² tumor in her sole, we observed immediate relief of her systemic symptoms, with visual analogue scale improvement from 5 of 10 preoperatively to 2 of 10 5 days after surgery. There were no signs of recurrence during 2-year follow-up. This case highlights the significance of thorough history-taking as a fundamental tool for diagnosis even in the era of advanced technology, and that the awareness of tumor-induced osteomalacia should be raised. Otherwise, such a small localized soft tissue mass would seldom be associated with the severe systemic symptoms.

Clinical Characteristics and Surgical Outcomes of Sinonasal Lesions Associated With Tumor-Induced Osteomalacia

OBJECTIVE

To investigate the clinical characteristics and surgical outcomes of sinonasal tumors associated with tumor-induced osteomalacia (TIO).

STUDY DESIGN

Retrospective case series.

SETTING

Single tertiary center.

METHODS

We studied the clinical characteristics and surgical outcomes of 43 patients (22 male, 21 female) who had lesions in the nasal cavity and paranasal sinus associated with TIO and underwent surgery between August 2006 and November 2019.

RESULTS

The mean ± SD duration between the onset of symptoms and surgery was 3.9 ± 2.6 years. The most common tumor site was the ethmoid sinus (76.7%), and the skull base was involved in 12 cases. Phosphaturic mesenchymal tumors were diagnosed in 41 patients, among whom there was 1 multifocal case. Another 2 cases involved odontogenic fibroma and hemangiofibroma, respectively. Serum phosphorus normalized in 39 cases within 4.4 ± 2.3 days, and serum fibroblastic growth factor 23 normalized within 1 day; clinical symptoms, however, gradually improved within several months after the first operation. There was no significant difference in the recovery rate between endoscopic and open surgery (P = 0.639). Two patients with recurrent cases and 2 with nonremission cases recovered after a sinonasal reoperation. The patient with a multifocal case recovered after the resection of the tumors in the ethmoid sinus and mandible. The overall recovery rate was 97.7%.

CONCLUSION

Most sinonasal tumors associated with TIO are located in the ethmoid sinus, and the skull base is involved in some cases. Complete excision of the tumor leads to recovery, and endoscopic surgery could achieve recovery rates similar to those of open surgery.

Mutational landscape and genetic signatures of cell-free DNA in tumour-induced osteomalacia

Tumour‐induced osteomalacia (TIO) is a very rare paraneoplastic syndrome with bone pain, fractures and muscle weakness, which is mostly caused by phosphaturic mesenchymal tumours (PMTs). Cell‐free DNA (cfDNA) has been regarded as a non‐invasive liquid biopsy for many malignant tumours. However, it has not been studied in benign tumours, which prompted us to adopt the targeted next‐generation sequencing approach to compare cfDNAs of 4 TIO patients, four patients with bone metastasis (BM) and 10 healthy controls. The mutational landscapes of cfDNA in TIO and BM groups were similar in the spectrum of allele frequencies and mutation types. Markedly, deleterious missense mutations in FGFR1 and loss‐of‐function mutations in MED12 were found in 3/4 TIO patients but none of BM patients. The gene ontology analysis strongly supported that these mutated genes found in TIOs would play a potential role in PMTs' process. The genetic signatures and corresponding change in expression of FGFR1 and FGF23 were further validated in PMT tissues from a test cohort of another three TIO patients. In summary, we reported the first study of the mutational landscape and genetic signatures of cfDNA in TIO/PMTs.

Surgical Treatment and Outcomes for Sinonasal and Skull Base Phosphaturic Mesenchymal Tumors

OBJECTIVE

To describe our clinical experience with surgical treatments for sinonasal phosphaturic mesenchymal tumors diagnosed at our institution.

STUDY DESIGN

Retrospective case series.

SETTING

Affiliated Sixth People's Hospital, Shanghai Jiao Tong University.

SUBJECTS AND METHODS

We retrospectively reviewed the medical records of 10 patients diagnosed with phosphaturic mesenchymal tumors associated with tumor-induced osteomalacia between December 2014 and October 2019.

RESULTS

There were 4 men and 6 women with a disease course of 1 to 19 years. All patients exhibited hypophosphatemia and tumor-induced osteomalacia. The tumor was located in the sinonasal region, frontal bone, and temporal bone in 8 patients, 1 patient, and 1 patient, respectively. Technetium-99m octreotide scintigraphy was used for tumor localization in 4 cases. Six patients underwent endoscopic resection; the remaining 4 underwent unilateral transorbital anterior and posterior ethmoid artery ligation + endoscopic resection, endoscopic resection + skull base repair, internal carotid artery stenting + transcatheter arterial embolization + temporal bone tumor excision + adipose tissue plugging, and endoscopic resection + transfrontal craniotomy (n = 1 each). Two patients had a history of incomplete endoscopic resection. All patients achieved clinical remission and normalized biochemical indices after surgery. Only 1 patient developed recurrence and died of a brain hernia.

CONCLUSIONS

A diagnosis of sinonasal phosphaturic mesenchymal tumors should be based on a combination of clinical, imaging, and pathological findings. Technetium-99m octreotide scintigraphy helps in locating the tumor. Complete surgical excision guarantees clinical remission, and preoperative transcatheter arterial embolization or feeding artery ligation may reduce intraoperative bleeding in cases of highly vascularized tumors.

Infiltrative nature of tumor-induced osteomalacia lesions in bone: Correlation between radiological and histopathological features

OBJECTIVE

Tumor-induced osteomalacia is a rare paraneoplastic syndrome usually caused by phosphaturic mesenchymal tumors, which commonly occur in bone. This study aimed to investigate the radiological features of tumor-induced osteomalacia lesions in bone, and their correlation with its histopathology.

MATERIALS AND METHODS

This study included 13 patients with tumor-induced osteomalacia treated between January 2000 and April 2018 at our hospital. All patients were surveyed to detect the tumor causing the condition. Diagnostic imaging studies of the suspected tumors were obtained before tumor removal. We evaluated the radiological features of all tumors, investigated histopathological findings in 10 cases that underwent surgery, and obtained evaluable tumor specimens.

RESULTS

The tumors were classified into the following three types by CT: sclerotic (n = 4), lytic (n = 7), and mixed (n = 2). In two cases, lytic lesions focally invaded the surrounding cancellous bone, detected by the soft tissue-window of CT, not the bone-window. Histopathology revealed inter-trabecular invasion in all cases, regardless of radiological features. Osteoclasts were seen in lytic types, and creeping substitution-like thickened trabecular bone and calcification were observed in sclerotic types. In all cases, focal invasion of the tumor into cortical bone was seen.

CONCLUSIONS

Tumor-induced osteomalacia lesions in bone showed a wide variety of radiological features, and tended to invade into cancellous and cortical bone. These findings suggest that extended curettage or resection of thinned cortical bone may be necessary. This might improve the cure rate of surgeries for tumor-induced osteomalacia lesions in bones.

Tumor-induced osteomalacia with the culprit lesion located in the palm: a case report

Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome. We herein report a rare case of TIO in a 58-year-old Chinese man who presented with a large lump in the right palm. Clinical, biochemical, and radiological assessments were performed. Laboratory examination showed severe hypophosphatemia, phosphaturia, an elevated serum alkaline phosphatase level, and an elevated serum fibroblast growth factor 23 (FGF-23) level. Dual-energy X-ray absorptiometry showed low bone mineral density. Magnetic resonance imaging revealed an irregular mass located in the right palm and abnormal findings in several metacarpal bones. During the operation, the surgeons found that the tumor had penetrated the surrounding muscles. The tumor had unique characteristics of local tissue invasion. The patient’s symptoms fully resolved and his serum phosphorus level normalized, although his serum FGF-23 level remained slightly high in the postoperative phase. Our findings suggest that in some patients with TIO, the serum phosphorus level might return to the normal range despite a relatively high postoperative serum FGF-23 level. These patients should be kept under close observation and regularly surveyed for any evidence of a residual tumor.

Comparison of surgical treatments of tumor-induced osteomalacia in different locations in the lower limbs: A retrospective study

Tumor-induced osteomalacia (TIO) is a rare disease that behaves benignly. Very few reports about the features of the responsible tumors according to anatomical locations have been presented.In this retrospective study of 53 patients with TIO-associated tumors in the foot/ankle, tibia and femur, we compared preoperative, postoperative, and follow-up courses, including alkaline phosphatase, phosphorus, and fibroblast growth factor 23, to compare the characteristics of TIO-associated tumors in these 3 locations (level of evidence: therapeutic level III).Patients in the foot/ankle group had longer disease courses and therefore a significantly higher complication rate (P < .001). All TIO-associated tumors in the foot/ankle group involved soft tissue (P = .021), whereas most lesions in the tibia group involved bone, and therefore had much higher concentrations of alkaline phosphatase (P = .020). Additionally, serum phosphorus took much longer to normalize after surgery in the foot/ankle group than that in the other 2 groups (P = .004). Consequently, symptom remission was much better in the tibia and femur groups (P = .008). Moreover, the Ki 67 index in TIO-associated tumors was significantly higher in the foot/ankle group (P < .001) and the recurrence rate in this group was markedly higher (P = .002).The TIO-associated tumors in the foot/ankle are characteristically of occult onset, more soft-tissue involvement, and more readily recurrence. More knowledge and examinations are necessary to enable early diagnosis, radical treatments, and minimize recurrence. New therapies are welcomed and needed.

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.

Phosphaturic mesenchymal tumors: what an endocrinologist should know

Tumor-induced osteomalacia (TIO), also known as "oncogenic osteomalacia", is a rare cause of osteomalacia. TIO often has an insidious onset characterized clinically by progressive muscle weakness and bone pain with fractures. The hallmark biochemical finding is a persistent low serum phosphorus concentration due to renal phosphate wasting. The vast majority of cases of TIO result from production of the phosphaturic hormone fibroblast growth factor 23 (FGF23) by a histologically distinctive mesenchymal tumor, termed "phosphaturic mesenchymal tumor" (PMT). Circulating FGF23 induces internalization of renal sodium/phosphate co-transporters resulting in reduced proximal tubular phosphate reabsorption. FGF23 also inhibits production of 1α,25-dihydroxyvitamin D which is inappropriately low or normal in the context of hypophosphatemia. Diagnosis is often delayed owing to the rarity of the condition and an underappreciation for the role of phosphorus as a cause for the constellation of symptoms. Primary treatment for TIO is identification of the offending tumor and surgical removal. However, these tumors are notoriously difficult to find, precluding the opportunity for a curative surgery in many. In such cases, phosphate and calcitriol therapy is used to improve symptoms and heal the osteomalacia. Recently, molecular genetic studies have shown recurrent genetic events in PMT, including the novel fusions FN1-FGFR1 and less commonly FN1-FGF1. These fusion events are hypothesized to result in autocrine/paracrine signaling loops within the tumor, spurring tumorigenesis. This review will cover the clinical features, imaging characteristics, pathologic features, molecular genetic aspects, and therapy of PMT, with a brief discussion of other neoplasms that may cause TIO.

Total hip/knee arthroplasty in the treatment of tumor-induced osteomalacia patients: More than 1 year follow-up

Background

Tumor-induced osteomalacia (TIO) may result in a better prognosis after complete resection of the causative neoplasm. However, tumors located proximal to the articular surface of the metaphysis remain largely uninvestigated.

Methods

A retrospective study of sixteen patients was undertaken to evaluate treatment of tumors with joint arthroplasty and tumor resection. The bone metabolism index, hip/knee joint function, arthroplasty complications and symptoms were followed up for at least 12 months in each patient.

Results

All patients presented with neoplasms situated in the articular surface of the metaphysis, with 13 cases undergoing hip arthroplasty and 3 undergoing knee arthroplasty. Treatment of the tumors with joint arthroplasty and tumor resection significantly and rapidly ameliorate bone metabolism indexes in patients with TIO (p<0.01), with no identified tumor recurrence. The joint function evaluation score was improved in 15 patients (93.75%). Complications in these patients included post-operative pain, joint squeaking and secondary hyperparathyroidism.

Conclusions

Joint arthroplasty that includes tumor-expanding resection appears to be a safe and appropriate method for the treatment of TIO patients with a neoplasm located in the metaphysis proximal to the articular surface.

Level of evidence

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

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.

Tumour-induced osteomalacia: a literature review and a case report

Tumour-induced osteomalacia (TIO) is a rare paraneoplastic syndrome characterised by severe hypophosphataemia and osteomalacia, with renal phosphate wasting that occurs in association with tumour. The epidemiology likewise aetiology is not known. The clinical presentation of TIO includes bone fractures, bone and muscular pains, and sometimes height and weight loss. TIO may be associated with mesenchymal tumours which may be benign or malignant in rare cases. Mesenchymal tumour itself may be related to fibroblast growth factor 23 (FGF23), which is responsible for hypophosphataemia and phosphaturia occurring in this paraneoplastic syndrome. Hypophosphataemia, phosphaturia and elevated alkaline phosphatase are the main laboratory readings that may lead to more precise investigations and better diagnosis. Finding the tumour can be a major diagnostic challenge and may involve total body magnetic resonance imaging, computed tomography and scintigraphy using radiolabelled somatostatin analogue. The treatment of choice for TIO is resection of a tumour with a wide margin to insure complete tumour removal, as recurrences of these tumours have been reported. We provide here an overview on the current available TIO case reports and review the best practices that may lead to earlier recognition of TIO and the subsequent treatment thereof, even though biochemical background and the long-term prognosis of the disease are not well understood. This review also includes a 4-year-long history of a patient that featured muscular pains, weakness and multiple stress fractures localised in the hips and vertebra with subsequent recovery after tumour resection. Because the occurrence of such a condition is rare, it may take years to correctly diagnose the disease, as is reported in this case report.