To study the clinicopathologic features of phosphaturic mesenchymal tumor.

The clinical and pathologic data of ten cases with phosphaturic mesenchymal tumor were evaluated, in the ten patients, six were males and four were females.Their age at the time of operation ranged from 23 to 55 years old.All cases had a history of chronic bone pain, arthralgia, limitation in movement for 1 to 13 years.Morphology and immune phenotype of phosphaturic mesenchymal tumor were observed.

Hypophosphatemia and byperphosphaturia were found in all patients.The diameters of tumor ranged from 0.8 cm to 5.0 cm.Microscopically, the tumors were composed of various mesenchymal cells, including spindled fibroblast-like cells, adipocytes, chondroid cells and mucinous cells, the tumor cells were rich in blood vessels.Four cases were also dystrophic calcification with an unusual flocculent or "grungy" pattern.Bone shell was formed surrounding the tumors which occured in soft tissue in three cases.Mitotic figures were rare in eight cases.In two cases however, mitotic figures and bizarre cells were commonly encountered.On immunohistochemical study, the tumor cells were all positive to vimentin and CD56.NSE was positive in seven and Bcl-2 was positive in three cases.The staining for desmin, S-100 and AE1/AE3 was negative.Ki67 proliferation index was 1%~5% in eight cases and 20%~30% in two case.

Most of the phosphaturic mesenchymal tumors are either benign or low grade malignant mesenchymal tumors.They can be mistaken as other neoplasms due to the morphologic heterogeneity.Clinical features and laboratory investigation results are helpful correct diagnosis phosphaturic mesenchymal tumor.