CD3 + CD20 + T cells (TB cells) are a subset of lymphocytes in the human body that are associated with inflammation. They originate from T cells interacting with B cells, and their levels are abnormally elevated in individuals with immune disorders, as well as in some cancer patients. The interplay between tumor immunity and inflammation is intricate, yet the specific involvement of TB cells in local tumor immunity remains uncertain, with limited research on their subtypes.Lung cancer surgical samples were stained using multi-color immunofluorescence to study the subtypes and distribution patterns of TB cells.TB cells were confirmed to exist in a scattered pattern within tertiary lymphoid structures (TLS) in lung cancer tissues, with higher abundance in mature TLS. In subtype analysis, the CD4-CD8- double-negative TB cell subtype was predominant, comprising over 90% in samples with abundant TLS infiltration and over 60% in samples with poor infiltration. This was followed by the CD4 + CD8- and CD4-CD8 + single-positive TB cell subtypes, while the CD4 + CD8 + double-positive TB cell subtype was nearly absent. During the maturation of TLS, the proportion of B cells gradually increased, while the proportion of CD4-CD8- T cell subtype decreased.TB cells extensively infiltrate the TLS regions in tumor tissues, with the double-negative subtype being predominant, potentially playing a crucial regulatory role in the local tumor immune microenvironment. This finding could facilitate the advancement of novel cancer treatment strategies.© 2025. The Author(s).