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

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

ABSTRACT

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

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.

Tumor-induced osteomalacia: An overview

Tumor-induced osteomalacia (TIO) is rare paraneoplastic syndrome of hypophosphatemic osteomalacia, caused by phosphaturic factors secreted by small mesenchymal origin tumors with distinct pathological features, called 'phosphaturic mesenchymal tumors'. FGF23 is the most well-characterized of the phosphaturic factors. Tumors are often small and located anywhere in the body from head to toe, which makes the localisation challenging. Functional imaging by somatostatin receptor-based PET imaging is the first line investigation, which should be followed with CT or MRI based anatomical imaging. Once localised, complete surgical excision is the treatment of choice, which brings dramatic resolution of symptoms. Medical management in the form of phosphate and active vitamin D supplements is given as a bridge to surgical management or in inoperable/non-localised patients. This review provides an overview of the epidemiology, pathophysiology, pathology, clinical features, diagnosis, and treatment of TIO, including the recent advances and directions for future research in this field.

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

BACKGROUND

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

CASE PRESENTATION

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

CONCLUSION

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

Tumor-induced Osteomalacia in a Boy with Maxillary Ossifying Fibroma

Tumor-induced osteomalacia (TIO) is a rare, paraneoplastic disorder of hypophosphatemia associated with elevated tumor-produced fibroblast growth factor 23 (FGF23). Maxillofacial tumors are rarely involved in TIO, especially maxillary TIO in children. We present a 14-year-old boy with osteomalacia and high serum levels of FGF23, a hormone associated with decreased phosphate resorption, due to a maxillary tumor. The patient was treated with oral phosphorus and calcitriol, and surgical removal of the tumor was performed. After 21 months follow-up, he was pain free and had returned to full activity. We review the reported pediatric cases of TIO in the maxillofacial and oral region and discuss the management of these patients considering the published evidence.

Sinonasal phosphaturic mesenchymal tumour: radiation oncologist's perspective

Tumour-induced osteomalacia is a rare cause of osteomalacia, the majority of which is of mesenchymal origin. Oncogenic osteomalacia is a potentially curable condition caused by phosphaturic mesenchymal tumours. We present the case of a woman in her 30s with a sinonasal phosphaturic mesenchymal tumour, treated with surgical excision followed by adjuvant intensity-modulated radiotherapy and subsequent adjuvant chemotherapy. The patient experienced minimal adverse effects during radiation. There was good local control and cosmetic outcomes with no radiation-related toxicity at a follow-up period of 32 months.

Occipital bone and tumor-induced osteomalacia: a rare tumor site for an uncommon paraneoplastic syndrome

INTRODUCTION

Tumor-induced osteomalacia (TIO) is an uncommon paraneoplastic syndrome due to the overproduction of fibroblast growth factor 23 (FGF23). It is predominantly caused by mesenchymal tumors and cured upon their complete removal. Non-surgical treatment is an alternative option but limited to specific clinical conditions.

METHODS

We report a challenging case of TIO caused by a tumor involving the occipital bone. We also performed a literature review of TIO caused by tumors localized at this site, focusing on clinical findings, treatment, and outcomes.

RESULTS

The patient, a 62-year-old male, presented with a long-lasting history of progressive weakness. Biochemical evaluation revealed severe hypophosphatemia due to low renal tubular reabsorption of phosphate with raised intact FGF23 values. A 68 Ga-DOTATATE PET/TC imaging showed a suspicious lesion located in the left occipital bone that MRI and selective venous catheterization confirmed to be the cause of TIO. Stereotactic gamma knife radiosurgery was carried out, but unfortunately, the patient died of acute respiratory failure. To date, only seven additional cases of TIO have been associated to tumors located in the occipital bone. Furthermore, the tumor involved the left side of the occipital bone in all these patients.

CONCLUSION

The occipital region is a difficult area to access so a multidisciplinary approach for their treatment is required. If anatomical differences could be the basis for the predilection of the left side of the occipital bone, it remains to be clarified.

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.

Tumor-Induced Osteomalacia: A Systematic Clinical Review of 895 Cases

Tumor-induced osteomalacia (TIO) is a rare and largely underdiagnosed paraneoplastic condition. Previous reviews often reported incomplete data on clinical aspects, diagnosis or prognosis. The aim of this study was to present a systematic clinical review of all published cases of TIO. A search was conducted in Pubmed, Embase, Web of Science from inception until April 23rd, 2020. We selected case reports and case series of patients diagnosed with TIO, with information on tumor localization and serum phosphate concentration. Two reviewers independently extracted data on biochemical and clinical characteristics including bone involvement, tumor localization and treatment. 468 articles with 895 unique TIO cases were included. Median age was 46 years (range 9 months-90 years) and 58.3% were males. Hypophosphatemia and inappropriately low or normal 1,25-dihydroxyvitamin D levels, characteristic for TIO, were present in 98% of cases. Median tumor size was 2.7 cm (range 0.5 to 25.0 cm). Serum fibroblast growth factor 23 was related to tumor size (r = 0.344, P < 0.001). In 32% of the cases the tumor was detected by physical examination. Data on bone phenotype confirmed skeletal involvement: 62% of cases with BMD data had a T-score of the lumbar spine ≤ - 2.5 (n = 61/99) and a fracture was reported in at least 39% of all cases (n = 346/895). Diagnostic delay was longer than 2 years in more than 80% of cases. 10% were reported to be malignant at histology. In conclusion, TIO is a debilitating disease characterized by a long diagnostic delay leading to metabolic disturbances and skeletal impairment. Increasing awareness of TIO should decrease its diagnostic delay and the clinical consequences.

Tumor-induced Osteomalacia: A Systematic Review and Individual Patient's Data Analysis

CONTEXT

Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome, usually caused by small, benign, and slow-growing phosphaturic mesenchymal tumors. Clinically, TIO is characterized by renal phosphate leak, causing hypophosphatemia and osteomalacia. This review was performed to assess the clinical characteristics of TIO patients described worldwide so far.

EVIDENCE ACQUISITION

On June 26, 2021, a systematic search was performed in Medline, Google Scholar, Google book, and Cochrane Library using the terms: "tumor induced osteomalacia," "oncogenic osteomalacia," "hypophosphatemia." There were no language restrictions. This review was performed according to Preferred Reporting Items for Systematic reviews and Meta-Analyses criteria.

EVIDENCE RESULTS

Overall, 1725 TIO cases were collected. TIO was more frequent in adult men, who showed a higher incidence of fractures compared with TIO women. The TIO-causing neoplasms were identified in 1493 patients. The somatostatin receptor-based imaging modalities have the highest sensitivity for the identification of TIO-causing neoplasms. TIO-causing neoplasms were equally located in bone and soft tissues; the latter showed a higher prevalence of fractures and deformities. The surgery is the preferred TIO definitive treatment (successful in > 90% of patients). Promising nonsurgical therapies are treatments with burosumab in TIO patients with elevated fibroblast growth factor-23 levels, and with radiolabeled somatostatin analogs in patients with TIO-causing neoplasm identified by somatostatin receptor-based imaging techniques.

CONCLUSION

TIO occurs preferentially in adult men. The TIO clinical expressiveness is more severe in men as well as in patients with TIO-causing neoplasms located in soft tissues. Treatments with burosumab and with radiolabeled somatostatin analogs are the most promising nonsurgical therapies.

Infigratinib Reduces FGF23 and Increases Blood Phosphate in Tumor‐Induced Osteomalacia

Tumor‐induced osteomalacia (TIO) is a rare paraneoplastic syndrome caused by ectopic production of fibroblast growth factor 23 (FGF23) by phosphaturic mesenchymal tumors (PMTs). Acting on renal tubule cells, excess FGF23 decreases phosphate reabsorption and 1,25‐dihydroxy‐vitamin D (1,25D) production, leading to hypophosphatemia, impaired bone mineralization, pain, and fractures. Fibronectin 1‐fibroblast growth factor receptor 1 (FN1‐FGFR1) gene fusions have been identified as possible drivers in up to 40% of resected PMTs. Based on the presumptive role of FGFR1 signaling by chimeric FN1‐FGFR1 proteins, the effectiveness of infigratinib, a FGFR1‐3 tyrosine kinase inhibitor, was studied in an open‐label, single‐center, phase 2 trial. The primary endpoint was persistent normalization of blood phosphate and FGF23 after discontinuation. Four adults with TIO (two nonlocalized, two nonresectable PMTs) were treated with daily infigratinib for up to 24 weeks. All patients had a favorable biochemical response that included reduction in intact FGF23, and normalization of blood phosphate and 1,25D. However, these effects disappeared after drug discontinuation with biochemistries returning to baseline; no patients entered biochemical remission. In the two patients with identifiable tumors, 68Gallium (68Ga)‐DOTATATE and 18Fluoride (18F)‐Fluorodeoxyglucose (FDG) PET/CT scans showed a decrease in PMT activity without change in tumor size. Patients experienced mild to moderate, treatment‐related, dose‐limiting adverse events (AEs), but no serious AEs. Three patients had dose interruptions due to AEs; one patient continued on a low dose for the entire 24 weeks and one patient stopped therapy at 17 weeks due to an AE. The study closed early due to a failure to meet the primary endpoint and a higher‐than‐expected incidence of ocular AEs. Infigratinib treatment lowered FGF23, increased blood phosphate, and suppressed PMT activity, confirming the role of FGFR signaling in PMT pathogenesis. However, treatment‐related AEs at efficacy doses and disease persistence on discontinuation support restricting the use of infigratinib to patients with life‐limiting metastatic PMTs. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Phosphaturic Mesenchymal Tumor in the Maxillofacial Region: A Diagnostic Dilemma

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

A rare combination of tumor-induced osteomalacia caused by sinonasal glomangiopericytoma and coexisting parathyroid adenoma: case report and literature review

BACKGROUND

Tumor-induced osteomalacia (TIO) is a rare, acquired disease of renal phosphate wasting and disturbed vitamin D homeostasis as a result of the action of a phosphaturic protein - FGF-23, produced by a neoplasm. Although the clinical and biochemical profile of the syndrome is characteristic, it remains underreported and unrecognized by clinicians. Hyperparathyroidism is rarely associated with oncogenic osteomalacia, but it should be considered because of potentially life-threatening hypophosphatemia caused by both conditions.

CASE PRESENTATION

We report a case of a 42-year-old woman admitted to the Department of Otolaryngology of the Military Institute of Medicine in Warsaw for the endoscopic resection of hormonally active glomangiopericytoma extending into the anterior skull base. She presented with a 5-year history of musculoskeletal pain and progressive weakness of the extremities which finally led her to become bedridden. After the excision of the tumor her symptoms and laboratory results gradually improved except increasing PTH serum levels. Further examination revealed a parathyroid proliferative tumor, which was surgically removed. The patient walked without aids at follow-up 16 months after the surgery.

CONCLUSIONS

This case is unusual because of tumor-induced osteomalacia and parathyroid adenoma occurring concomitantly. Further investigations of FGF-23 and PTH interplay should be conducted to elucidate the pathogenesis of hyperparathyroidism and tumorigenesis in some cases of TIO. By presenting this case, we wanted to remind clinicians of a rare and misdiagnosed paraneoplastic syndrome and highlight the importance of monitoring PTH concentrations during the follow-up of patients with TIO.

Vitamin D deficiency osteomalacia triggered by long-term social withdrawal and unbalanced diet in a Japanese middle-aged subject: A case report

INTRODUCTION

Osteomalacia is caused by an increase in the number of osteoids owing to mineralization failure. There are various causes of osteomalacia, such as hypophosphatemia due to excess production of fibroblast growth factor 23, vitamin D deficiency, insufficient vitamin D action, and renal tubular disorders.

PATIENT CONCERNS

A 53-year-old man with bone pain and gait disturbance was referred to our institution. At the age of 35, he developed atopic dermatitis. He had eyesight deterioration due to atopic cataracts when he was 37 years old. Subsequently, he stayed home all the time, and his eating habits were unbalanced for a long period of time. Although he had atopic dermatitis, he did not take allergen-free diets, and he did not use sunscreen. Furthermore, when he was 43 years old, he failed to flex his legs and suffered gait disturbance.

DIAGNOSIS

Hypocalcemia and hypophosphatemia were observed as follow: calcium, 5.5 mg/dL; adjusted calcium, 6.9 mg/dL; inorganic phosphorous, 1.9 mg/dL. In addition, intact parathyroid hormone levels were as high as 277.4 pg/mL, and 1, 25-(OH)2 vitamin D and 25-(OH) vitamin D levels were markedly reduced: 1, 25-(OH)2 vitamin D, ≤4 pg/mL; 25-(OH) vitamin D, 11.0 ng/mL. Fibroblast growth factor 23 levels did not increase. Alkaline phosphatase (ALP) and bone-type ALP (BAP) levels were high: ALP, 784 U/L; BAP, 159.2 μg/L (reference range: 3.7-20.9 μg/L). Based on these findings, we diagnosed this patient with vitamin D-deficient osteomalacia triggered by long-term social withdrawal and an unbalanced diet.

INTERVENTIONS AND OUTCOMES

After hospitalization, to treat vitamin D-deficient osteomalacia, we started to administer 1 μg/day of alfacalcidol and 3 g/day of calcium lactate. Approximately one month later, 1,25-(OH)2 vitamin D levels increased to 214 pg/mL. Consequently, calcium and inorganic phosphorus were also increased up to 7.8 mg/dL and 3.9 mg/dL, respectively, and intact parathyroid hormone was decreased to 132.0 pg/mL.

CONCLUSIONS

We should bear in mind the possibility of osteomalacia triggered by social withdrawal and vitamin D deficiency even in middle-aged subjects.

Challenges in the management of tumor-induced osteomalacia (TIO)

Tumor-induced osteomalacia (TIO), also known as oncogenic osteomalacia, is a rare acquired paraneoplastic disease, which is challenging to diagnose and treat. TIO is characterized by hypophosphatemia resulting from excess levels of tumor-secreted fibroblast growth factor 23 (FGF23), one of the key physiological regulators of phosphate metabolism. Elevated FGF23 results in renal phosphate wasting and compromised vitamin D activation, ultimately resulting in osteomalacia. Patients typically present with progressive and non-specific symptoms, including bone pain, multiple pathological fractures, and progressive muscle weakness. Diagnosis is often delayed or missed due to the non-specific nature of complaints and lack of disease awareness. Additionally, the disease-causing tumour is often difficult to detect and localize because they are often small, lack localizing symptoms and signs, and dwell in widely variable anatomical locations. Measuring serum/urine phosphate should be an inherent diagnostic component when assessing otherwise unexplained osteomalacia, fractures and weakness. In cases of hypophosphatemia with inappropriate (sustained) phosphaturia and inappropriately normal or frankly low 1,25-dihydroxy vitamin D, differentiation of the potential causes of renal phosphate wasting should include measurement of FGF23, and TIO should be considered. While patients experience severe disability without treatment, complete excision of the tumour is typically curative and results in a dramatic reversal of symptoms. Two additional key current unmet needs in optimizing TIO management are: (1 and 2) the considerable delay in diagnosis and consequent delay between the onset of symptoms and surgical resection; and (2) alternative management. These may be addressed by raising awareness of TIO, and taking into consideration the accessibility and variability of different healthcare infrastructures. By recognizing the challenges associated with the diagnosis and treatment of TIO and by applying a stepwise approach with clear clinical practice guidelines, patient care and outcomes will be improved in the future.

Radiotherapy for a rare phosphaturic mesenchymal tumor in the middle ear presenting with oncogenic osteomalacia: A case report

RATIONALE

Phosphaturic mesenchymal tumor (PMT) is a rare neoplasm causing oncogenic osteomalacia. Surgery remains the definitive treatment for PMT, and radiotherapy is seldom employed. However, surgery for PMT involving the head and neck is often difficult due to the local invasion and complicated anatomy. We report the first case of PMT, which was successfully treated with the combination of radiotherapy and supplementation of activated vitamin D.

PATIENT CONCERNS

A 55-year-old woman suffered from pain in the hip and bilateral femur. Serum phosphate and calcium decreased to abnormal levels. Serum alkaline phosphatase and fibroblast growth factor 23 increased to abnormal levels. The hearing loss of the right ear had continued and a middle ear tumor was revealed.

DIAGNOSES

Subsequent biopsy provided the diagnosis of PMT that caused oncogenic osteomalacia. These clinical and pathological characteristics were consistent with and provided the final diagnosis of benign PMT.

INTERVENTIONS

Surgery of the PMT was difficult and the patient underwent radiotherapy. The prescribed dose was 36 Gy in 10 fractions. Simultaneously, the patient started supplementation of 1,25-dihydroxyvitamin D3 (1-2 μg/day) and continued for 2 years.

OUTCOMES

Near-complete resolution of the symptoms was achieved and abnormal laboratory values recovered. At 5 years of follow-up, the irradiated tumor showed no regrowth. Severe hearing loss of the right ear was not observed.

LESSONS

Radiotherapy was effective for the PMT and could be an important treatment option for inoperable cases.

Successful Treatment of Tumor-Induced Osteomalacia by Multidisciplinary Therapy with Radiation to Intracranial Fibromyxoid Tumor

Background

Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome caused by protein fibroblast-growth-factor-23 (FGF-23) secreting tumors. Complete tumor resection is the current standard of care for TIO; however, some patients may develop tumor recurrence. Due to the rarity of this paraneoplastic syndrome, the role of radiotherapy is unclear. This case is worth reporting because it adds to our knowledge some insights about the potential role of radiotherapy in this rare condition. Case Presentation. After multidisciplinary consultation, in July 2015, postoperative adjuvant radiotherapy was offered to a 52-year-old man with a multiple recurrent ossifying fibromyxoid tumor in the right frontal sinus causing TIO. The patient had a history of multiple bone fractures and pain since more than 20 years. The tumor had been removed in 2003 for the first time. Subsequent endoscopic resections of the tumor had been performed for recurrences of TIO in May 2012, October 2013, and July 2015. Starting from October 2015, external beam radiotherapy was delivered with a volumetric modulated arc technique to the tumor bed with a daily dose of 2 Gy up to a total dose of 60 Gy. After five years from treatment, the patient is free from local tumor relapse, TIO progression, and radiation-induced side effects.

Conclusions

Radiotherapy may provide long-term TIO remission and tumor control, thus being a treatment option in cases where surgery is unfeasible or unsuccessful.

Hypophosphatemic Osteomalacia in a Young Adult

Tumor-induced osteomalacia (TIO), otherwise known as oncogenic osteomalacia, is a rare paraneoplastic syndrome, characterized by hypophosphatemia due to decreased tubular reabsorption and low or inappropriately normal level of active vitamin D. The syndrome, first recognized by Robert McCance in 1947, is well described in the medical literature. However, the diagnosis can be delayed due to the nonspecific nature of its presentation. The tumor responsible for TIO produces fibroblast growth factor 23 (FGF-23) which plays a role in regulating renal handling of phosphate and 25-hydroxyvitamin D 1α-hydroxylase activity. Chronic hypophosphatemia eventually leads to inadequate bone mineralization and osteomalacia. The diagnosis should be considered when a patient presents with low phosphate and osteomalacia or rickets and should be differentiated from other disorders of phosphate metabolism such as X-linked, autosomal dominant and recessive hypophosphatemic rickets, and acquired cause like vitamin D deficiency. The localization of the tumor is rather difficult as the tumor can be too small and be anywhere in the body. A combination of thorough physical examination, laboratory tests, and proper imaging is needed for the diagnosis. Surgical removal of the tumor often leads to complete resolution of the syndrome. If the tumor is undetectable or unresectable, then phosphate and vitamin D supplements should be considered.

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.

Peptide Receptor Radionuclide Therapy for a Phosphaturic Mesenchymal Tumor

Tumor-induced osteomalacia is a very rare paraneoplastic syndrome. It can be caused by phosphaturic mesenchymal tumor (PMT), a generally benign tumor that produces fibroblast growth factor 23 (FGF-23), which can cause a severe renal phosphate wasting syndrome. Upon complete surgical removal of the tumor, FGF-23 normalizes and the osteomalacia is cured. In cases in which surgery is not feasible, radiofrequency ablation (RFA) is the treatment of choice. We describe a case with a PMT situated in the sacrum, in close proximity to the sacral plexus. Both surgery and RFA were considered potentially nerve damaging. Since the tumor showed expression of somatostatin receptors, we opted for a peptide receptor radionuclide therapy (PRRT) with ¹⁷⁷Lu-DOTATOC. However, the therapy did not show the expected success, since the FGF-23 level had even temporarily increased. The patient was then successfully treated with RFA. A partial remission of the tumor was achieved and FGF-23 levels nearly normalized. Despite some severe neurological side effects, the patient showed a remarkable clinical improvement, with no symptoms of osteomalacia within a few weeks.

Tumor-induced rickets-osteomalacia: an enigma

Objective We report a case of pediatric thoracic tumor-induced osteomalacia (TIO) causing severe hypophosphatemic rickets with delayed diagnosis and emphasize on timely management of this rare entity. Case presentation A young boy presented with rickets since five years of age. Biochemical evaluation revealed hypophosphatemia, hyperphosphaturia, elevated alkaline phosphatase and normal calcium levels. Initially managed as hereditary hypophosphatemic rickets, he was given phosphorus supplements and calcitriol. Despite the therapy, skeletal deformities worsened requiring surgical corrections. Subsequently, he developed iatrogenic tertiary hyperparathyroidism for which he underwent total parathyroidectomy. Later on, he was found to have fibroblast growth factor-23 secreting thoracic mass (10.5 cm in largest dimension) which was excised with significant post operative improvement. Histopathology showed phosphaturic mesenchymal tumor-mixed connective tissue variant, confirming the diagnosis of TIO. Conclusion TIO, a correctable cause of hypophosphatemic rickets, should be considered in children presenting with hypophosphatemic rickets with evident mass on examination/imaging and in refractory cases.