Given the tumor-promoting role of M2-like macrophages, the aims of our study were to assess if these tumor-associated macrophages (TAM): (i) could be specifically detected in vivo in the TME in a preclinical model of TNBC using 99mTc-Tilmanocept SPECT imaging and (ii) could be modulated by PU-WS13, a cell-permeable 6-amino-purine-based selective inhibitor of GRP94. The gene discussed is HSP90B1; the disease is neoplasm.