This is a randomized, double-blind, placebo-controlled presurgical trial of 0.228% 4-hydroxy-tamoxifen (4-OHT) gel vs. oral tamoxifen (TAM) 20 mg daily. The study population will consist of 112 pre- and postmenopausal women with any grade DCIS, ER positive, non-palpable DCIS with no evidence of invasion found on diagnostic core needle biopsy (DCNB). In order to accrue a total of 112 participants with DCIS over a period of 22 months, 20 eligible participants total will be screened at the three participating institutions per month with a planned average monthly recruitment of 5 participants total per month. We assume that 22 women (20% of the recruited population, 11 women per arm) will be inevaluable because of the presence of unanticipated invasive disease in the therapeutic surgical excisional (TSE) specimen, or the absence of residual DCIS in the TSE, so that a total of 90 women (45 per arm) will be evaluable for the study endpoints. These estimates are based on numbers from the Lynn Sage Database of NU: over the six-year period 2000-2005, the fraction of women diagnosed with DCIS on core needle biopsy who were found to have no residual DCIS in the TSE was 2.5% and that of women with invasive disease (T1a or greater) in the TSE when the DCNB showed pure DCIS was 13.3%, very similar to the data reported by Bonnett et. al. [56] who found that 13% of pure DCIS lesions seen on DCNB (29/122) were in fact invasive in the TSE. With regard to racial/ethnic groups, 25.6% of the DCIS population at NU were of non-European ancestry (18% African, 4% Hispanic, 3.5% other). WU has higher fractions of African American women with DCIS (24% and 21% respectively).