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Aims To determine if the frequency of CD103+ T cells among background lymphocytes is associated with non-haematopoietic metastasis in samples of clinically concerning unexplained lymphadenopathy.Methods We retrospectively reviewed clinical flow cytometry data from 126 lymph node (LN) samples including 36 involved by metastatic non-haematopoietic malignancy and 90 control LNs (54 benign/reactive and 36 lymphomas). We evaluated the frequency of CD103+ cells among CD3+, CD3+CD4+ and CD3+CD8+ T cell subsets. Immunohistochemistry was used to visualise CD103 expression in a limited number of cases.Results CD103 expression in ≥3% of total CD3+ T cells and ≥7% of CD3+CD8+ T cells correlated with the presence of metastatic non-haematopoietic malignancy in LNs, and differentiated LNs with metastasis from control LNs with sensitivities of 75% (95% CI 59% to 86%) and 78% (95% CI 62% to 88%) and specificities of 100% (95% CI 96% to 100%) and 99% (95% CI 94% to 100%), respectively.Conclusion Increased frequency of CD103+ T cells is associated with metastatic non-haematopoietic malignancies in excisional and core needle biopsies of clinically concerning lymphadenopathy.