Immunohistochemistry is commonly used in the diagnosis and classification of lymphomas. Some of the key markers and their uses in lymphomas include:
CD20 - B cell marker, used to confirm the B cell nature of B cell lymphomas. Positive in follicular lymphoma, diffuse large B cell lymphoma, etc.
CD3 - T cell marker, used to confirm the T cell origin of T cell lymphomas and lymphomas like anaplastic large cell lymphoma.
CD5 - Often positive in chronic lymphocytic leukemia/small lymphocytic lymphoma and mantle cell lymphoma. Helps distinguish these lymphomas from diffuse large B cell lymphoma.
CD10 - Often positive in follicular lymphoma, germinal center diffuse large B cell lymphoma and mantle cell lymphoma. Helps classify follicular vs diffuse large B cell lymphomas.
BCL2 - Highly positive in follicular lymphoma. Helps confirm the follicular lymphoma diagnosis.
MUM1/IRF4 - Positive in germinal center diffuse large B cell lymphoma and primary mediastinal large B cell lymphoma. Helps classify diffuse large B cell lymphomas into different subtypes.
Ki-67 - Used as a proliferation marker to assess the aggressiveness of lymphomas like follicular lymphoma. Higher Ki-67 suggests more aggressive disease.
CD68 - Macrophage marker used to rule out Hodgkin lymphoma, which is MAC-1 positive. Helps distinguish Hodgkin vs non-Hodgkin lymphomas.
Other markers - CD79a, PAX5, CD23, CD30, ALK-1, EBER, etc. are used less commonly but may provide additional useful information in specific case types.
In conclusion, immunohistochemistry is a significant tool for accurately classifying different lymphomas in accordance with the WHO categorization system. It aids in the classification of the many subtypes of B cell and T cell lymphomas as well as the distinction between B cell, T cell, and Hodgkin lymphomas.