Moreover, our observation of the immune checkpoint molecule, HLA-G, significantly upregulated in the SPA subtype and its counterpart LILRB2 predicted to be significant and highly inhibited implicate the involvement of the immune tolerance or anti-tumor immune escape processes in early-stage SPA, although CTLA-4 and PD-1 may not yet be expressed at early-stage. Here, LILRB2 is linked to neoplasm.