Phosphaturic mesenchymal tumors: A review and update.

Perhaps the rarest cause of osteomalacia is that caused by a neoplasm, so-called "tumor-induced osteomalacia" (TIO). Although very rare cases of TIO have been associated with carcinomas and syndromes such as neurofibromatosis type-1 and McCune-Albright syndrome, the overwhelming majority of TIO is caused by tumors of mesenchymal origin. Although it was historically felt that almost any mesenchymal tumor type could occasionally result in TIO, it has become increasingly clear over the past several decades that almost all cases of mesenchymal tumor-associated TIO are caused by a single entity, known as "phosphaturic mesenchymal tumor" (PMT). This article will review historical aspects of this tumor, as well as its clinical, morphological, immunohistochemical and molecular genetic features. The distinction of PMT from its many potential morphological mimics is discussed in detail.