Additionally, to verify the robustness of the proteomic data in low-risk cluster 2 and unassigned tumors (both groups were represented by a lower number of tumor samples), we verified the upregulation of a prospective cell surface drug targeting ATP8A1 in cluster 2 PPGLs and SLC7A1 in unassigned PPGLs. This evidence concerns the gene SLC7A1 and neoplasm.