CD45 (LCA) is also known as leukocyte common antigen (LCA). It is a sensitive marker for lymphoid cells. In the most general form it is often used as part of a panel for undifferentiated tumors or so-called “small round blue cell tumors.” Such a screening panel usually includes:
- CD45 (lymphoid)
- AE1/AE3 (carcinoma/epithelial)
- S-100 (neural/melanocytic)
- Desmin (sarcoma/muscular origin)
- CD99 (PNET if other markers are negative).
The biggest pitfall is to remember that CD45 is not perfectly sensitive. Anaplastic large cell lymphoma (ALCL) may not express CD45 in 1/4th to 1/3rd of cases. Classical Hodgkin Lymphoma cells are “classically” negative for CD45. Mature plasma cells/plasma cell neoplasms are usually negative for CD45 (CD138 will also stain epithelial cells in addition to plasma cells).
Photomicrographs
![CD45 - Classical Hodgkin Lymphoma](https://www.pathmd.com/wordpress/wp-content/uploads/2017/10/NSCHL_CD45-1024x768.jpeg)
![CD45 - Non-Hodgkin Lymphoma](https://www.pathmd.com/wordpress/wp-content/uploads/2017/10/NHL_CD45_1-1024x682.jpg)
References
Wick, MR. “Immunohistochemical approaches to the diagnosis of undifferentiated malignant tumor.”Annals of Diagnostic Pathology12(2008):72-84.
Bone Marrow IHC. Torlakovic, EE, et. al. American Society for Clinical Pathology Pathology Press © 2009. pp. 97.