CD3 protein is a T cell marker, which is only found in T cells. In malignant lymphoma, CD3 is a broad T cell line limiting antigen, which can be detected in 80% ~ 97% of T cell lymphoma. Mature T-cell lymphoma may lose CD3 antigen, such as mycosis fungoides, peripheral T-cell lymphoma, anaplastic large cell lymphoma. CD3 is an important marker for the classification of lymphoma and lymphoid leukemia.