Solid tumours represent complex cellular ecosystems where interactions between diverse cell populations drive disease progression and treatment response. However, the organisation of tumour-associated cells into functional niches remains poorly understood. Spatial transcriptomics techniques like Visium integrate transcriptome-wide gene expression with spatial information, enabling unbiased exploration of signalling and regulatory mediators within spatial units. Using Visium, we are analysing 200 breast tumours to develop a spatially resolved taxonomy of breast cancer. Our initial analyses have focused on lymphoid aggregates in the tumour microenvironment, revealing distinct zones that resemble cellular niches found in lymph nodes. We also identify a gene expression signature that specifically detects germinal centres, a defining feature of mature tertiary lymphoid structures linked to improved outcomes. Ultimately, our spatial breast cancer atlas will offer a comprehensive view of immune neighbourhoods in breast tumours.