[Value of MDM2, CDK4 and SATB2 immunohistochemistry in histologic diagnosis of low-grade osteosarcoma]

To investigate the value of combined application of MDM2, CDK4 and SATB2 immunohistochemistry in pathological diagnosis of low-grade osteosarcoma.

Forty-seven cases of low grade osteosarcoma, including low grade central osteosarcoma (n=20) and parosteal osteosarcoma (n=27), were selected from Shanghai Jiaotong University Affiliated the Sixth People's Hospital. The clinical, radiography and histopathology were reviewed. The sensitivity and specificity of MDM2, CDK4 and SATB2 immunohistochemistry in the diagnosis of low-grade osteosarcoma were assessed along with an evaluation of their expressions in fibrous dysplasia, desmoplastic fibroma, low-grade fibrosarcoma and other fibrous tumors.

Low-grade osteosarcoma had protracted clinical course, occurring mostly in elder adults and mainly involving long bones. Radiographic studies showed that low-grade central osteosarcoma had a mainly malignant lytic presentation, however about 5/18 of tumors overlapping with intermediate and benign bone diseases, while parosteal osteosarcoma was characterized by a densely sclerotic malignant appearance. Histologically, low-grade osteosarcomas were characterized by well-differentiated spindle tumor cells, various mature tumor bones and an aggressive growth pattern. The positive expression rates of MDM2 and CDK4 in low-grade osteosarcoma were 74.5% and 55.3%, respectively. Eighty-three percent of low-grade osteosarcoma expressed one or both markers. Low-grade osteosarcoma and fibrous dysplasia were both positive for SATB2, while desmoplastic fibroma, low-grade fibrosacoma and other fibrous tumors were negative for SATB2.

Accurate diagnosis of low-grade osteosarcoma should be based on combination of clinical presentation, imaging and histopathology, with immunohistochemistry as a diagnostic adjunct. Positive immunostaining for CDK4 and/or MDM2 supports the diagnosis of low-grade osteosarcoma, but the negative one does not rule out such lesion. The negative expression of SATB2 is helpful to exclude fibrous tumors originating from bone with the exception of fibrous dysplasia.