Oncogenic osteomalacia.

Severe osteomalacia (confirmed by the examination of thin undecalcified bone biopsy sections) associated with hypophosphataemia developed in a 60 year old woman. A skeletal x-ray survey showed a lytic lesion in the right proximal femur, and this was curetted, showing a vascular tumour. The patient's symptoms improved almost immediately and serum phosphate concentrations returned to normal. Some time later the syndrome and the tumour recurred. The tumour was excised, and again the patient improved. Morphological examination of the tumour showed a lesion which closely resembled haemangiopericytoma. Review of published reports confirmed that most reported cases have been associated with "vascular" mesenchymal tumours both in intraosseous and extraosseous sites.