Similarly, in lung cancer [23,48] or osteosarcoma lung metastases [32], RTM-TAMs are characterized by high levels of MARCO, scavenger receptor (SIGLEC1 (CD169)), and fatty acid-binding protein 4 (FABP4) expression, which is also characteristic of alveolar macrophages. The gene discussed is FABP4; the disease is osteosarcoma.