Inhibition of apoptosis seems to play an important role in the pathogenesis of marginal zone lymphoma. Apoptosis regulator B-cell lymphoma 10 (BCL10) may show aberrant nuclear localization in some aggressive extracutaneous MALT lymphomas, often in association with a MALT1 gene t(11;18)(q21;q21) translocation. The possible occurrence of this association in primary cutaneous marginal zone lymphoma (PCMZL) remains insufficiently explored. The aim of this study was to evaluate BCL10 protein expression pattern and its possible relationship to the presence of t(11;18)(q21;q21) and other MALT1 gene abnormalities in PCMZL and to assess their clinical significance. The study included 42 consecutive PCMZL patients diagnosed on the basis of the World Health Organization/European Organization for the Research and Treatment of Cancer classification criteria. BCL10 expression was immunohistochemically evaluated in all cases, whereas t(11;18)(q21;q21) reverse transcriptase polymerase chain reaction amplification was performed on 21 samples. In addition, the presence of other MALT1 gene translocations was explored in 26 samples by interphase fluorescence in situ hybridization using a MALT1 locus-specific probe. We observed the presence of aberrant nuclear BCL10 expression in a significant number of PCMZL cases (36%, 15/42). This aberrant expression was significantly related to the development of extracutaneous disease. In contrast, neither the t(11;18)(q21;q21) translocation nor other MALT1 gene translocations could be demonstrated. t(11;18)(q21;q21), strongly linked to extracutaneous MALT lymphomas, does not seem to play a role in PCMZL. The participation of other MALT1 gene translocations in PCMZL pathogenesis seems also unlikely.