ARPC1B and breast carcinoma: ARPC1B expression was also related to the Scarff-Bloom-Richardson grade of mammary carcinomas (Supplementary information, Table S1), since 19.9% of grade III patients overexpressed ARPC1B, compared to 8.3% for grade II and only 3.3% for grade I. In contrast, the limited overexpression of the paralogous ARPC1A gene had no value for the prognosis.