Tumor-induced osteomalacia: long-term follow-up of two patients cured by removal of their tumors

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.

Oncogenic osteomalacia of the cervical spine: a rare case of curative resection and reconstruction

Oncogenic osteomalacia (OO) is a rare paraneoplastic syndrome, with only 100 reported cases in the literature. The majority of OO-associated mesenchymal tumors are due to a lesion called phosphaturic mesenchymal tumor, mixed connective tissue (PMTMCT) variant. There have been only 6 reported cases of OO of the spine. With this paper the authors present a case of OO of the cervical spine in a patient who initially presented with multiple pathological fractures of unknown cause, and who eventually underwent staged C-5 spondylectomy followed by circumferential stabilization. Resection of the cervical lesion led to resolution of his hypophosphatemia and prevention of any further pathological fractures. The authors describe a rare cervical neoplasm, its treatment, and review the literature on this rare bony pathological entity.

Oncogenic osteomalacia caused by a phosphaturic mesenchymal tumor of the thoracic spine

Phosphaturic mesenchymal tumors that cause the paraneoplastic syndrome known as oncogenic osteomalacia are rare. The authors report on the case of a 57-year-old man with a history of osteomalacia and in whom was diagnosed a thoracic spine tumor at the T-4 level. Complete tumor resection was accomplished. The histological diagnosis was phosphaturic mesenchymal tumor (mixed connective tissue variant). After lesion removal, the paraneoplastic syndrome resolved. At the 24-month follow-up, no recurrence of the disease was observed. The clinical presentation, surgical technique, and follow-up in this case were reviewed in detail.

Case report: Solitary plasmacytoma of bone with oncogenic osteomalacia: recurrence of tumour confirmed by PET/CT. A case report with a review of the radiological literature

We describe a case of oncogenic osteomalacia secondary to solitary plasmacytoma of the vertebral body of T3. The patient presented with symptoms of hypophosphataemia. Following the initial diagnosis, the lesion was surgically resected with good results, although several follow-up procedures, including bone grafting, were necessary to stabilize the thoracic spine. The lesion recurred almost 15 years after its initial resection, again presenting with hypophosphataemia and neurological symptoms suggestive of local tumour recurrence. A variety of radiological examinations were performed in an attempt to confirm and localize recurrent tumour, including bone scintigraphy, (111)indium octreotide scintigraphy, high-resolution CT and MRI of the thoracic spine, but these yielded only negative or equivocal results owing, in part, to the presence of extensive post-operative changes, and also to a difference in the MR signals of the recurrent and original tumours. Positron emission tomography (PET/CT) demonstrated a solitary focus of intense fluorodeoxyglucose uptake in the T3 vertebral body, enabling a definitive diagnosis of recurrent plasmacytoma. This case illustrates the diagnostic value of PET/CT in the setting of challenging post-operative changes in the surrounding tissue and in the appearance of the tumour itself. Relevant related imaging literature is also reviewed.

Secondary hyperparathyroidism as a palpable intrathyroid parathyroid gland in a patient with hypophosphatemic osteomalacia

Secondary hyperparathyroidism is sometimes seen in patients with hypophosphatemic osteomalacia after long-term oral phosphate therapy. Parathyroidectomy is sometimes needed for the correction of hypercalcemia in these patients, and is rarely performed in patients without hypercalcemia. A 46-year-old female patient had hypophosphatemic osteomalacia with unknown cause and secondary hyperparathyroidism. A palpable neck mass developed after long-term oral phosphate therapy. An intrathyroid parathyroid gland was confirmed through partial thyroidectomy and parathyroidectomy. Renal phosphate wasting decreased strongly, and serum parathyroid hormone was in the normal range after the operation. A correction of secondary hyperparathyroidism may partially overcome hyperphosphaturia in some patients with hypophosphatemic rickets.

Most osteomalacia-associated mesenchymal tumors are a single histopathologic entity: an analysis of 32 cases and a comprehensive review of the literature

Oncogenic osteomalacia (OO) is a rare paraneoplastic syndrome of osteomalacia due to phosphate wasting. The phosphaturic mesenchymal tumor (mixed connective tissue variant) (PMTMCT) is an extremely rare, distinctive tumor that is frequently associated with OO. Despite its association with OO, many PMTMCTs go unrecognized because they are erroneously diagnosed as other mesenchymal tumors. Expression of fibroblast growth factor-23 (FGF-23), a recently described protein putatively implicated in renal tubular phosphate loss, has been shown in a small number of mesenchymal tumors with known OO. The clinicopathological features of 32 mesenchymal tumors either with known OO (29) or with features suggestive of PMTMCT (3) were studied. Immunohistochemistry for cytokeratin, S-100, actin, desmin, CD34, and FGF-23 was performed. The patients (13 male, 19 female) ranged from 9 to 80 years in age (median 53 years). A long history of OO was common. The cases had been originally diagnosed as PMTMCT (15), hemangiopericytoma (HPC) (3), osteosarcoma (3), giant cell tumor (2), and other (9). The tumors occurred in a variety of soft tissue (21) and bone sites (11) and ranged from 1.7 to 14 cm. Twenty-four cases were classic PMTMCT with low cellularity, myxoid change, bland spindled cells, distinctive "grungy" calcified matrix, fat, HPC-like vessels, microcysts, hemorrhage, osteoclasts, and an incomplete rim of membranous ossification. Four of these benign-appearing PMTMCTs contained osteoid-like matrix. Three other PMTMCTs were hypercellular and cytologically atypical and were considered malignant. The 3 cases without known OO were histologically identical to the typical PMTMCT. Four cases did not resemble PMTMCT: 2 sinonasal HPC, 1 conventional HPC, and 1 sclerosing osteosarcoma. Three cases expressed actin; all other markers were negative. Expression of FGF-23 was seen in 17 of 21 cases by immunohistochemistry and in 2 of 2 cases by RT-PCR. Follow-up (25 cases, 6-348 months) indicated the following: 21 alive with no evidence of disease and with normal serum chemistry, 4 alive with disease (1 malignant PMTMCT with lung metastases). We conclude that most cases of mesenchymal tumor-associated OO, both in the present series and in the reported literature, are due to PMTMCT. Improved recognition of their histologic spectrum, including the presence of bone or osteoid-like matrix in otherwise typical cases and the existence of malignant forms, should allow distinction from other mesenchymal tumors. Recognition of PMTMCT is critical, as complete resection cures intractable OO. Immunohistochemistry and RT-PCR for FGF-23 confirm the role of this protein in PMTMCT-associated OO.

Disorders of phosphate metabolism--pathomechanisms and management of hypophosphataemic disorders

Hypophosphataemia does not necessarily indicate phosphate (Pi) depletion. In acute emergencies such as septicaemia, alkalosis or re-feeding, hypophosphataemia may result from redistribution of Pi from the extracellular to the intracellular space. Hypophosphataemia from true Pi depletion gives rise to skeletal (osteomalacia) and extraskeletal (myopathy, cardiomyopathy) disorders. It is practically never the result of diminished nutritional intake. The most severe syndromes of Pi depletion result from diminished tubular Pi re-absorption and renal Pi wasting. In the differential diagnosis mainly four conditions have to be considered: (i) tumour-associated osteomalacia, (ii) X-linked hypophosphataemia (XLH), (iii) autosomal dominant hypophosphataemia, and (iv) hypercalcaemic renal phosphate wasting. Recent molecular insight has put fibroblast growth factor (FGF-23) into the centre of pathophysiological considerations because of (i) overproduction (tumour-associated osteomalacia) or (ii) hypothetically, accumulation resulting from mutations causing resistance to processing or degradation (autosomal dominant hypophosphataemia) or (iii) loss-of-function of a protease (PHEX) interfering with FGF-23 breakdown (XLH). In oncogenic osteomalacia the treatment of choice is resection of the tumour. Recently, pharmacological treatment has also become possible, i.e. administration of octreotide. XLH and autosomal dominant hypophosphataemia must be managed by oral administration of phosphate and calcitriol. In patients with gastrointestinal intolerance to phosphate or with severely symptomatic bone disease, prolonged intravenous administration of Pi is necessary.

Oncogenic osteomalacia: case report and review of head and neck associated tumours

Oncogenic osteomalacia is an uncommon syndrome characterized by mineral metabolism abnormalities that disappear after the resection of an associated tumour. Head and neck is the second most frequent location of these tumours. We describe a case with an ethmoido-frontal phosphaturic mesenchymal tumour and review oncogenic osteomalacia-associated tumours. Among 21 cases found, 57 per cent affected the sinonasal area and 20 per cent the mandible. The diagnosis of the tumour lasted a mean of 4.7 years from the onset of osteomalacia, and most of them showed a significant vascular component. An aggressive surgical approach is recommended.

Tumor-induced osteomalacia

Tumor-induced (oncogenic) osteomalacia is a rare clinicopathologic entity in which the clinical signs and symptoms of osteomalacia and the specific laboratory abnormalities of hypophosphatemia, hyperphosphaturia, and low serum levels of 1,25(OH)2 vitamin D are associated with the finding of a neoplastic process in the patient. To date, less than 100 cases of oncogenic osteomalacia have been described. We report a new case of adult-onset hypophosphatemic osteomalacia leading to the discovery of an asymptomatic phosphaturic mesenchymal lung tumor. Complete resection of the pulmonary neoplasia was followed by rapid normalization of the laboratory findings and clinical remission. The clinical, laboratory, and histopathologic spectrum of tumor-induced osteomalacia is presented, and the postulated mechanism of this condition is discussed in light of the relevant literature. The presence of occult neoplasms should be considered in cases of unexplained adult osteomalacia, with the physician's efforts being rewarded by the dramatic cure that follows excision of the tumor.