BCL10 (also known as CLAP/ CIPER/cE10/CARMEN) was cloned from break point of (1;14)(p22;q32) translocation which is shown in low grade MALT lymphomas (B cell lymphomas of mucosa-associated lymphoid tissue). This molecule has been reported to encode a protein of 233 amino acids containing CARD (caspase recruitment domain) in 13-101 aa, and CARD family of proteins such as CARD9, CARD10, CARD11 and CARD14. It is found that BCL10 has an important role for antigen receptor signaling in B and T cells to NF-?B activation from the study using BCL10 knockout mice. BCL10 transgenic mice showed specific expansion of marginal zone B-cells in the spleen. This observation suggests strong expression of BCL10 by (1;14)(p22;q32) translocation is important for lymphomagenesis of MALT lymphoma. mRNA expression of BCL10 is commonly shown in normal tissues but highly expressed in lymphoid tissues, and also highly expressed in MALT lymphomas. The expression of the protein and its cellular localization were studied by immunostaining using anti-BCL10 monoclonal antibody by Ming-Qing Du et al. They reported that BCL10 was expressed in lymphoid tissue but not in various other tissues with the exception of breast, and it is localized in cytoplasm, while strong BCL10 expression in both nucleus and cytoplasm was found in MALT lymphomas with (1;14)(p22;q32) translocation. Furthermore, they also reported that nuclear BCL10 expression also occurs frequently in MALT lymphomas without t(1;14)(p22;q32), and t(11;18)(q21;q21) closely correlated with BCL10 nuclear expression. These results suggest that nuclear BCL10 expression may be important in the development and advancement of MALT lymphoma. Recently, it has been found that BCL10 and MALT1 form a complex within the cell, and these proteins synergize in the activation of NF-?B. MALT1 has been known to be involved in MALT lymphoma associated t(11;18)(q21;q21), which cause expression of fusion product between the N-terminal API2 and C-terminal MALT1. API-MALT1 fusion protein has been also reported to strongly activate NF-?B. These observations suggest unrelated translocations may contribute to the same malignant process.