To explore clonal relationships between MDL components, morphologically distinct regions of DCIS, LCIS and invasive tumours with a ductal or lobular growth pattern were laser capture‐dissected or needle‐dissected from seven cases (supplementary material, Table S1), and analysed for DNA copy number alterations by cCGH (MDL1–MDL4, n = 4) or nucleotide variation by exome sequencing (MDL4–MDL7, n = 4). Here, CLEC5A is linked to ductal breast carcinoma in situ.