Our observation is in contrast to previously published data that describe comparable stromal components in liver metastases and primary tumours.40 However, matched samples were only available in seven cases, and α-SMA staining was not performed for the matched dataset.40 Interestingly, a recent publication from the Stanger laboratory investigated the dynamic changes of the tumour stroma during progression from single metastatic cells to nanometastases, micrometastases, millimetastases and macrometastases in the KPCY mouse model. Here, ACTA1 is linked to neoplasm.