Our study shows that 61.25% of our patients with invasive ductal breast carcinomas overexpressed syndecan-1 within their carcinoma cells, whereas lacking it in the stroma (E+S−) and that 30% lacked syndecan-1 within the tumour cells but expressed it in their stroma (E−S+). This evidence concerns the gene SDC1 and invasive ductal breast carcinoma.