CD99 is a type I transmembrane glycoprotein encoded by the CD99 gene and the functions of CD99 in cells in which CD99 was highly expressed have been studied and they were as follows: cell death of thymocytes and T lymphocytes, migration through monocyte endothelial junctions by adhesion and diapedesis, cell-cell adhesion in lymphocytes, maintenance of cellular morphology in Hodgkin and Reed/Sternberg cells, and recruitment of T cells.
CD99 expression has been reported in many cell types, such as hematopoietic cells, endothelial cells, central nervous system ependymal cells, thymocytes, granular cells of the ovary, Sertoli cells, and pancreatic islet cells. And in tumors it expressed by virtually almost all Ewings sarcoma and primitive peripheral neuroectodermal tumors (ES/PNET) and demonstrates strong and diﬀuse membranous staining. Other tumors that may show CD99 expression include neuroendocrine carcinomas, mesenchymal chondrosarcomas, solitary fibrous tumors, synovial sarcomas, vascular tumors, small round blue cell tumors, lymphoblastic lymphoma, acute myeloid leukemia, and myeloid sarcoma.
Studies have shown that CD99 may be a sensitive marker for Ewing’s sarcoma and peripheral neuroectodermal tumors and may aid in the differential diagnosis of small blue cell tumors.
Synthetic peptide corresponding to CD99 residues within aa85‐C terminal of CD99 was used as an immunogen.
1.Gawon Choi, et al. Journal of Pathology and Translational Medicine 2016; 50: 361-368.
2.Ventura S, et al. Oncogene. 2016 Jul 28;35(30):3944-54.