FCN1 and colorectal carcinoma: The SPP1+ macrophages were specifically enriched in primary foci and liver metastases of CRC, and evidence from trajectory and tissue distribution analysis supports the hypothesis that they originate from monocytes recruited into colonic tissues and rapidly differentiate into macrophages, which then differentiate into monocyte-like FCN1+ macrophages that polarize toward C1QC+ macrophages and SPP1+ macrophages (Fig. 8B).