SOX9 and SATB2 immunohistochemistry cannot reliably distinguish between osteosarcoma and chondrosarcoma on biopsy material.

Limited tissue in biopsies of malignant bone lesions can preclude definitive subclassification, especially when cellular or matrix elements are sparse, absent, or confounding. It is uncertain whether immunohistochemistry for SOX9 (marker of chondrogenesis) and SATB2 (marker of osteoblastic differentiation) may be discriminatory tools toward osteosarcoma and chondrosarcoma. This study interrogated the preresection biopsies of a cohort of osteosarcoma and chondrosarcoma with SATB2 and SOX9 in tandem, to assess their value as diagnostic adjuncts as well as their concordance with the final resection diagnoses. SATB2 was expressed more frequently in osteosarcoma (46/53, 86%) than in chondrosarcoma (9/18, 50%); SOX9 was expressed in high frequencies in both osteosarcoma (52/53, 98%) and chondrosarcoma (17/18, 94%), and SATB2 and SOX9 were coexpressed in both osteosarcoma (46/53, 89%) and chondrosarcoma (8/18, 44%). There exists significant overlap in the expression of SATB2 and SOX9 in osteosarcoma and chondrosarcoma. These markers are not expressed in a distribution that is unique enough for application toward this particular diagnostic differential.