BACKGROUND: Immune responses in a tumour microenvironment can be evaluated by analysing tumour-infiltrating lymphocyte (TIL) density; this has been verified in the clinical setting. Although there are many reports on TIL density in primary tumours, little is known about its density in recurrent tumours. METHODS: Of 300 patients treated with neoadjuvant chemotherapy during the study period, 29 were considered for evaluation of TIL density in primary and recurrent tumours. We performed a retrospective analysis of the association between TIL density and prognosis. RESULTS: TIL density was significantly lower in recurrent tumours than in primary tumours (P = 0.007). There was no correlation between post-recurrence survival and TIL density in core-needle biopsy specimens obtained from primary tumours (P = 0.837). However, patients with high TIL density in recurrent tumours had significantly better post-recurrence survival than did the corresponding group with low TIL density (P = 0.041). Multivariate analysis revealed that high TIL density contributed significantly towards improving post-recurrence survival in all patients (P = 0.035; hazard ratio, 0.167). CONCLUSIONS: In recurrent breast cancer, a decrease in TILs density was observed as compared to the primary tumour, and this affects the poor prognosis after relapse.