AbstractLangerhans cells (LCs) are dendritic, antigen‐presenting cells found in the epidermis. This study investigates the effect of early breast cancer on the expression of CD1a and S100 antigens by these cells. LCs were counted and expressed as cells/mm of epithelial basement membrane on biopsies from the skin overlying the tumour and from biopsies distant from the tumour. A control study was performed on normal breast skin, not adjacent to a lesion, from women with benign breast disease.The LC count of 18 patients undergoing biopsy for benign breast disease indicated a mean of 26 cells mm [95 percent confidence interval (CI) 23–29] and a S100/CD1a ratio of 70 percent.In 35 cases of early breast cancer, the CD1a‐positive LC count in the epidermis overlying the carcinoma (mean 26/mm; 95 per cent CI 23–29) was similar, but the count made on biopsies distant from the tumour (mean 21/mm; 95 per cent CI 19–23) was significantly smaller. The percentage ratio of S100/CD1a LCs was 71 per cent over the carcinoma and 84 per cent in the distant biopsies.The changes were not associated with the presence of nodal metastases or the oestrogen and progesterone status of the primary tumour.The reduction in LC numbers provides a link between decreased monocyte function and the decreased skin hypersensitivity responses found in patients with brea