ACTA1 and neoplasm: Conversely, in the tumour stroma, several cells with spindle‐like morphology were triple‐positive for calretinin, α‐SMA, and nuclear pSmad3, confirming that MCs have activated TGF‐β–Smad3‐dependent signalling, undergone an MMT, invaded the stroma, and trans‐differentiated into CAFs (Figure 5G–I).