Oncogenous osteomalacia. Review of the world literature of 42 cases and report of two new cases.

The clinical and biochemical data in 42 reported cases of oncogenous osteomalacia are reviewed, and data in two previously unreported cases are recorded. It is likely that the syndrome is more common than suggested by the paucity of reports and may account for a substantial fraction of nonfamilial, adult-onset "idiopathic" osteomalacia. Tumors associated with the syndrome are characteristically benign, of mesenchymal origin, highly vascular, and composed principally of giant and spindle cells. Complete excision of tumors results in cure of the osteomalacia in the majority of patients. The syndrome presumably represents an instance of humor-induced phosphaturia but supporting experimental data are scanty. Plasma levels of 1,25-dihydroxycholecalciferol are uniformly low, and treatment with this metabolite is generally very effective; however, abnormal vitamin D metabolism cannot by itself account for the syndrome.