Assessment of calcitriol and inorganic phosphate therapy before cure of oncogenous osteomalacia by resection of a mixed mesenchymal tumor.

A 57 year old white male with oncogenous osteomalacia due to a mixed mesenchymal tumor was evaluated by sequential histologic and metabolic studies over a period of 33 mos prior to identifying the location of the tumor. On the basis of these studies we conclude: (i) disorders of the enterohepatic circulation and/or acceleration of metabolism of calcitriol are not responsible for its diminished level in oncogenous osteomalacia, (ii) the Von Kossa stain is preferred to the modified Masson in evaluating osteomalacia, (iii) avascular necrosis of the femoral head may be part of the syndrome, (iv) heterogeneity may be the hallmark of the responsible mesenchymal tumor and account for the different histological interpretations in the literature, (v) in compliant patients with oncogenous osteomalacia, calcitriol and Pi therapy may be effective.