SPP1 and esophageal squamous cell carcinoma: In-situ mIHC staining using antibodies against CD68, SIRPα, and SPP1 in our in-house ESCC cohort 1 patients identified macrophages co-expressing SPP1 and SIRPα and SPP1 + macrophages possessed a high proportion of SIRPα expression (Fig. 1J, K and Table S1).