CD22 and Burkitt lymphoma: The histological characteristics of BL include the following: Medium-sized and consistent atypical cells with basophilic cytoplasm and small nucleoli; observation of apoptosis and mitosis; the ‘starry sky’ phenomenon; a unique immunophenotype of atypical cells with the expression of IgM, CD10, CD38, CD43 and Bcl-6; the expression of the B-cell-associated antigens (CD20, CD19 and CD22); a Ki-67 proliferation index of ~100% (17); and usually no expression of Bcl-2 and TDT.