ERCC6L and breast cancer: Then, we used palpation to investigate mammary tumor onset in female mice and observed that both ERCC6L−/− PyMT and ERCC6L+/− PyMT mice had slowed mammary tumor onset, with median tumor latencies (T50) of 78.5 days (n = 19) and 68.5 days (n = 10), respectively, which were significantly higher than those of ERCC6L+/+ PyMT mice (T50 = 44 days; n = 10) (Fig. 5B).