HER2 signalling in breast cancer cells is critical in heregulin β1-induced up-regulation of vascular endothelial growth factor-C, an important regulator of tumour lymphangiogenesis33, and the HER2 protein expression level is significantly associated with vascular endothelial growth factor-C expression and tumour lymphangiogenesis in human breast cancer tissues34. The gene discussed is VEGFC; the disease is breast carcinoma.