We investigated the expression of Bcl10 gene mutations in mucosa-associated lymphoid tissue-type ocular adnexal lymphoma (OAL), atypical lymphoid hyperplasia (ALH), and reactive lymphoid hyperplasia (RLH) in the Chinese population and its role in clinical diagnosis and pathogenesis. Forty-three samples were collected during patient surgeries. Pathological diagnosis confirmed OAL in 23 cases, ALH in 10 cases, and RLH in 10 cases. Normal peripheral lymph tissues from 12 cases were used as negative controls. Bcl10 gene expression was examined using molecular biological methods, and DNA sequences and mutations were compared with published data. The protein expression of Bcl10 and nuclear factor kappaB (NF-κB) were detected with immunohistological and immunofluorescence colocalization. Bcl10 gene expression was detected in 15 OAL cases. Novel mutations were found in 11 cases. Notably, 1 mutation, which matched a published mutation, was detected in 1 ALH case; 1 novel mutation was found in 1 RLH case; and no Bcl10 gene mutation was found in controls. Most novel mutations were truncation mutations, resulting in a truncated protein product of 99 amino acids (compared to the full-length 233 amino acids; GenBank accession No. EF189176). Results of tests for abnormal Bcl10 gene expression in nuclei or cytoplasm were consistent with changes in NF-κB translocation. This report is the first of newly discovered mutations in the Bcl10 gene in the Chinese population. The distribution of the mutations is consistent with and more sensitive than that of the pathological diagnosis. These mutations can be used to identify the stage and clinical characteristics even when morphological changes are absent.