Home > A. Molecular pathology > CD99


MIM.313470 Xpter-p22.32

Wednesday 11 February 2004

The gene encoding CD99 surface antigen is located in the pseudoautosomal region (PAR) at the end of the short arm of the X and Y chromosomes. CD99 is a relatively non-specific marker for Ewing sarcoma and T-cell lymphoblastic lymphoma.

The monoclonal antibody 12E7 was raised against human leukemia T cells. It detects a 30,000 MW protein, now called CD99, which is expressed on all human tissues tested with the possible exception of spermatozoa.

Expression in normal cells

- ovarian granulosa cells
- pancreatic islets
- infant thymus
- Sertoli cells

Expression in tumors

- Ewing sarcoma/PNET (95% sensitive)
- lymphoblastic lymphoma (93%) (#8163272#)
- large cell lymphoma (20%) (#8163272#)
- small noncleaved cell lymphoma (5%) (#8163272#)
- T cell acute lymphoblastic lymphoma
- calcifying aponeurotic fibroma
- gastrointestinal stromal tumor (GIST)
- intraabdominal desmoplastic small round cell tumor (DSRCT) (23-35%)
- leukemia cutis
- nuchal fibromas
- sclerosing perineurioma (myxoid sclerosing type)
- rhabdomyosarcoma (membranous staining)
- sinonasal undifferentiated carcinoma
- small cell carcinomas of lung
- solitary fibrous tumor (SFT)
- synovial sarcoma (poorly differentiated, monophasic and myxoid types)
- Wilms tumors
- endometrial stromal tumors with sex cord differentiation

Negative staining: adult neuroblastoma


  • Ewing sarcoma: CD99 positivity
  • Ewing sarcoma: CD99 positivity
  • Ewing sarcoma: CD99 positivity