Small Cell Osteosarcoma

Note the resemblance of the tumor cells in the left half of the image to Ewing sarcoma. The similarities between small cell variant of osteosarcoma and Ewing sarcoma go beyond mere morphologic features. The immunohistochemical profile of the two tumors is similar. In addition, the most commonly found cytogenetic abnormality in Ewing sarcoma/PNET [t(11;22)] has also been reported in small cell osteosarcoma. This has led some authors to postulate that small cell osteosarcoma is a subtype of Ewing sarcoma.