The present study demonstrates for the first time that mRNA levels of COX-2, a well recognized functional marker for tumour progression, are highly correlated with VEGF-C mRNA levels in human breast cancer tissues and VEGF-C gene expression or secretion by breast cancer cell lines; that COX-2 or VEGF-C mRNA expression levels in breast cancer tissues are correlated with the expression of LYVE-1, a marker for lymphangiogenesis; that VEGF-C synthesis in breast cancer cells is stimulated, at least in part, by COX-2, EP1 and EP4 receptor activity. Here, PTGER1 is linked to breast cancer.