Estrogen induced proliferation of mutant cells is widely understood to be the one of major risk determining factor in the development of breast cancer. Hence determination of the Estrogen Receptor[ER] status is of paramount importance if cancer pathogenesis is to be detected and rectified at an early stage. Near Infrared Fluorescence [NIRf] Molecular Optical Imaging is emerging as a powerful tool to monitor bio-molecular changes in living subjects. We discuss pre-clinical results in our efforts to develop an optical imaging diagnostic modality for the early detection of breast cancer. We have successfully carried out the synthesis and characterization of a novel target-specific NIRf dye conjugate aimed at measuring Estrogen Receptor[ER] status. The conjugate was synthesized by ester formation between 17-β estradiol and a hydrophilic derivative of Indocyanine Green (ICG) cyanine dye, bis-1,1-(4-sulfobutyl) indotricarbocyanine-5-carboxylic acid, sodium salt. In-vitro studies regarding specific binding and endocytocis of the dye performed on ER+ve [MCF-7] and control [MDA-MB-231] adenocarcinoma breast cancer cell lines clearly indicated nuclear localization of the dye for MCF-7 as compared to plasma level staining for MDA-MB-231. Furthermore, MCF-7 cells showed ∼4.5-fold increase in fluorescence signal intensity compared to MDA-MB-231. A 3-D mesh model mimicking the human breast placed in a parallel-plate DOT Scanner is created to examine the in-vivo efficacy of the dye before proceeding with clinical trials. Photon migration and florescence flux intensity is modeled using the finite-element method with the coefficients (quantum yield, molar extinction co-efficient etc.) pertaining to the dye as obtained from photo-physical and in-vitro studies. We conclude by stating that this lipophilic dye can be potentially used as a target specific exogenous contrast agent in molecular optical imaging for early detection of breast cancer. © 2011 SPIE.