BCL-1 (B-cell lymphoma 1) has been linked to a pro-apoptotic gene in mucosa-associated lymphoid tissue (MALT) lymphomas. The BCL1 gene encodes for a T-cell receptor signaling downstream protein involved in nuclear factor kappaB activation. It is expressed in normal lymphoid tissues and in several B-non Hodgkin lymphomas, its aberrant function being related to the pathogenesis of certain subtypes. B-cell lymphoma 1 (BCL1) is not essential for actin polymerisation after FcgammaR stimulation in human fibroblasts. BCL1 expression within cell blocks facilitates a differential diagnosis of acinar cell carcinoma.