Copyright information:Taken from "Assessment of the proliferative, apoptotic and cellular renovation indices of the human mammary epithelium during the follicular and luteal phases of the menstrual cycle"Breast Cancer Research 2005;7(3):R306-R313.Published online 16 Feb 2005PMCID:PMC1143573.Copyright © 2005 Navarrete et al. licensee BioMed Central Ltd. The graphs that best represent the proliferation and the apoptotic indexes were the linear regression (a,c,e) and the polynomial curve (b,d,f), respectively. By superimposing the data after mathematically adjusting the mean visible time of Ki-67 expression [53] with that of the apoptotic index, one confirms that the maximum values for both indices coincide at about day 24 of the menstrual cycle (the point at which the linear regression and polynomial curves are tangential). Correlation of progesterone levels with apoptosis and proliferation irrespective of the stage of the menstrual cycle.