Oncogenic osteomalacia, which is characterized by renal
phosphate wasting, low serum 1, 25-dihydroxyvitamin D, and
osteomalacia, is caused by mesenchymal
neoplasms that are termed phosphaturic mesenchymal
tumors (
PMTs). As
PMTs are usually small and lack specific histological features, the pathological identification of
PMTs is difficult. Dentin matrix
protein 1 (DMP1) is an acidic
phosphoprotein expressed in mineralized tissues including bone, tooth, and hypertrophic cartilage. Increased expression of DMP1 gene in
PMTs has been reported by using differential
cDNA screening. In the present study, DMP1 expression in
PMTs and other soft tissue
tumors was analyzed immunohistochemically to verify its utility in the differential diagnosis of
PMTs. Anti-DMP1 polyclonal antibody was raised against the C-terminal sequence of DMP1. Three cases with
PMTs and 11 other soft tissue
tumors (two malignant
hemangiopericytomas, three
solitary fibrous tumors, three
synovial sarcomas, and three
malignant peripheral nerve sheath tumors) were analyzed for DMP1 expression. DMP1 expression was observed in all of the three cases with
PMTs, but never found in other soft tissue
tumors examined. DMP1 was detected in the extracellular matrix with myxomatous features or around capillary vessels, and in dystrophic calcified sites. Paranuclear DMP1 staining in the
tumor cells was also observed. These findings indicate that DMP1 immunohistochemistry is a useful tool for identifying
PMTs.