CD4 and thyroid nodule: We performed LASSO regression analysis incorporating demographic characteristics (age, gender), sonographic features (nodule size, echogenicity, composition, multifocality, boundary, and morphology), BRAFV600E mutation status, and comprehensive lymphocyte subset profiles (including T cell percentages, T cell absolute counts, CD4+ T cell counts, CD4+ T cell percentages, CD8+ T cell counts, CD8+ T cell percentages, NK cell counts, NK cell percentages, B cell counts, B cell percentages and CD4+/CD8+ radio) to identify the most discriminative predictors of thyroid nodule malignancy.