KRAS and neoplasm: In addition, in a Kras-mutated murine system, they observed an increase of macrophages in the animals expressing Lcn2 compared to those with deleted Lcn2. It has been demonstrated that at an early stage of pancreatic carcinogenesis, tumor-associated macrophages (TAMs) infiltrate the PDAC stroma, suggesting that the presence of TAMs is a pivotal and crucial initial process in PDAC development.