ESR1 and breast carcinoma: Junttila et al. previously analyzed expression of HER4 cleavable isoforms in 60 breast cancer specimens, and found predominance of the JM-a isoform as well as a correlation between each of higher JM-a, higher CYT-1, higher CYT-2 expression and lower histological grade, and ER/PR positivity [8, 18].