CD99 and neoplasm: Numerous studies have shown that nuclear atypia, high mitotic count (>4/10 HPF), tumor sizes, tumor sites, positive surgical margins, and necrosis are the most useful malignant indicators.[10,27,28] On immunohistochemical study, CD34, CD99, and Bcl-2 were previously thought to be the most useful positive immunohistochemical markers for SFT.