Lymphatic vessels are present in phosphaturic mesenchymal tumours.

Oncogenic osteomalacia (OO) is an acquired form of hypophosphataemic osteomalacia, which is associated most commonly with the development of a benign phosphaturic mesenchymal tumour mixed connective tissue type (PMTMCT). PMTMCTs are generally well vascularised tumours, and many have in the past been classified as haemangiomas and haemangiopericytomas. Although these tumours show some morphological variation, it has been proposed that they represent a distinct histopathological entity. Our aim in this study was to determine by immunohistochemistry the vascular profile of PMTMCT. Using monoclonal antibodies directed against several vascular markers, including the lymphatic endothelial cell antigens LYVE 1 and podoplanin, we found that PMTMCTs, in contrast to haemangiomas and haemangiopericytomas, contain lymphatic vessels. Taken with previous observations that PMTMCTs overexpress FGF23 and other gene products, this finding provides further evidence that most osteomalacia associated mesenchymal tumours represent a discrete pathological entity.