Targeting of tumoral tissues is one of the most promising approaches to improve both the efficacy and safety of anticancer treatments. The identification of valid targets, including proteins specifically and abundantly expressed in cancer lesions, is of utmost importance. Despite state‐of‐the‐art technologies, the discovery of cancer‐associated target proteins still faces the limitation, in human tissues, of antigen accessibility to suitable high‐affinity ligands such as human mAb bound to bioactive molecules. Terminal perfusion of tumor‐bearing mice or ex vivo perfusion of human cancer‐bearing organs with a reactive biotin ester solution has successfully led to the identification of novel accessible biomarkers. This methodology is however restricted to perfusable organs, and excludes most of the tissues of interest to targeted therapies, e.g. primary breast cancer and metastases. Herein, we report on the development of a new chemical proteomic method that bypasses the perfusion step and thus offers the potential to identify accessible molecular targets in virtually all types of animal and human tissues. We have validated our new procedure by identifying biomarkers selectively expressed in human breast carcinoma. Overall, this powerful technology may lay the ground not only for custom‐made therapies in cancer, but also for the development of therapies that need to be selectively delivered in a specific tissue.