However, there is an emerging group of neoplasms, including pancreatic endocrine neoplasms, gastric adenocarcinoma (Jung et al. 2002; Maitra et al. 2003) and osteosarcoma (OS) (Manara et al. 2006), in which CD99 expression is diffuse in benign diseases and absent in the malignant counterparts. The gene discussed is CD99; the disease is neoplasm.