SIGLEC12 encodes a human-specific sialic acid-binding immunoglobulin-like lectin expressed on epithelial and immune cells. While UniProt describes it as a putative adhesion molecule mediating sialic acid-dependent cell binding [UniProt annotation], the canonical sialic acid recognition property is compromised by a fixed human-universal missense mutation (R122C) present in all humans 1. Beyond adhesion, SIGLEC12 has recently emerged as a critical executor of necroptotic cell death: it undergoes dephosphorylation downstream of MLKL, interacts with the necroptotic machinery, and is cleaved by TMPRSS4 to generate a 20-kDa fragment that directly mediates plasma membrane rupture 2. This cleavage-dependent function is human-specific, as knockout of murine Siglec12 does not affect membrane rupture 2. Clinically, SIGLEC12 shows strong disease relevance in cancer. A polymorphic frameshift mutation eliminates full-length protein expression in ~60-70% of humans 1. Notably, despite loss of canonical ligand-binding, Siglec-XII still recruits the oncogenic phosphatase Shp2 and accelerates tumor growth 3. Advanced carcinomas show markedly elevated SIGLEC12 expression (~80% in late-stage colorectal and bladder cancers), correlating with poor prognosis, increased mortality, and upregulation of pro-oncogenic pathways 345. In renal and bladder cancers, elevated expression associates with immune checkpoint upregulation, suggesting potential for immunotherapy 45. Additionally, SIGLEC12 polymorphisms influence cardiovascular outcomes in hypertensive patients treated with antihypertensives 6.