OBJECTIVES/GOALS: Age-related lobular involution (LI) is a physiological process of breast epithelial regression that occurs primarily during perimenopause (ages 45-55); women in this age range for which the process of LI is delayed, defined as LI stagnation, show significantly increased risk of breast cancer as compared to LI progression patients. METHODS/STUDY POPULATION: The Mayo Clinic Benign Breast Disease (BBD) cohort includes ~1000 women who had multiple sequential benign biopsies. 103 patients were found to have sequential biopsies during the perimenopausal period, of which 10 eventually progressed to breast cancer. These patients were assessed for LI stagnation vs LI progression by quantifying 10 lobules per slide and comparing median acini number and median lobule size between initial and subsequent biopsies from the same patients. RNA was derived from whole tissue sections from the initial biopsies, and profiled using NanoString IO360 and BC360, which were normalized using RUVg methods. Differentially expressed genes associated with LI stagnation were defined as having two-tailed, unpaired p-values less than 0.05. RESULTS/ANTICIPATED RESULTS: Analysis showed subsetting patient sets by time between biopsies improves classification of stagnant vs. progression. Differential gene analysis identified 37 genes associated with LI stagnation and LI progression, and 20 of these genes were found to overlap a set of 128 gnese that were differentially expressed between women who subsequently developed breast cancer vs remained cancer-free. These genes represent potential biomarkers of processes that link LI stagnation and increased breast cancer risk. DISCUSSION/SIGNIFICANCE: In future studies, we intend to study these genes that were shown to be upregulated in LI stagnation for their association with subsequent development of breast cancer in independent cohorts of women with BBD. We will use this knowledge to improve individualized risk assessment, which will help focus surveillance and prevention strategies.