GRP and neoplasm: We revealed biological similarities in these tumors, including 15 genes overexpressed in all three types of ACTH-secreting tumors (POMC, NXPH4, RORB, SCIN, MIR137HG, PCSK1, CPNE4, EPHA4, LGI2, TMEM178B, ANK1, ANAPC1P1, FMO5, KCNE4, and ADCY2), as well as differentially expressed mRNAs in lung ACTH-secreting tumor encoding secretory proteins (GRP (gastrin releasing peptide) and CALCA (calcitonin)) that may potentially be detected in circulation.