EDN1 and ductal breast carcinoma in situ: Egidy et al (2000) demonstrated, using reverse transcriptase polymerase chain reaction (RT–PCR), increased expression of pre-pro ET-1 and ECE mRNA in colorectal adenomas compared with normal colon. Also, Alanen et al (2000) demonstrated that immunoreactivity for ET-1 in breast ductal carcinoma in situ (DCIS) specimens was significantly higher (P<0.005) than that in normal breast tissue. A further significant increase in immunoreactivity was found in invasive tumours compared with DCIS (P<0.02).