HMMR and neoplasm: However, Blg-Cre-driven HMMR overexpression in mammary glands did not prompt tumor development or cause atypical epithelial structures to appear (Supplementary Fig. 5) in virgin and parous mice followed for at least 47 weeks: Blg-Cre;HMMRTg/+, virgin n = 20 and parous n = 24; Blg-Cre;HMMRTg/Tg, virgin n = 25 and parous n = 25; and including controls HMMRTg/+ parous n = 3, and HMMRTg/Tg parous n = 3.