Mesenchymal tumor in the calcaneus with oncogenic osteomalacia: a case report

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.

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.

Ovarian cancer-related hypophosphatemic osteomalacia--a case report

CONTEXT

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

OBJECTIVE

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

DESIGN AND INTERVENTION

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

RESULTS

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

CONCLUSIONS

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