EGFR and neoplasm: The EGFR inhibitor erlotinib (m/z 394.1757 ± 0.001) and m/z 529.9846 ± 0.001 (tentatively identified as ATP/dGTP with an error of 0.69 ppm) show colocalization with tumor cluster#2, whereas m/z 558.2953 ± 0.001 (tentatively identified as lysoPC(18:2) with an error of 0.62 ppm) is found as part of a second tumor cluster#8.