The present invention relates to a compound or a pharmaceutically acceptable salt thereof having a chemical structure comprising: A compound or a pharmaceutically acceptable salt thereof of formula (I): (A)-x1-(B)-x2-(C), wherein (A) is at least one motif specifically binding to cell membranes of neoplastic cells; (B) at least one chelator moiety of radiometals; (C) a dye moiety; x1 is a spacer covalently connecting (A) and (B); x2 is a spacer or a chemical single bond connecting (B) and (C); wherein (C) has the formula wherein R1 to R4, R9, a, b, Y and X1 to X4 have the meaning as indicated in the claims and description. The invention further relates to compositions comprising said compounds as well as a method for detecting neoplastic cells in a sample in vitro with the aid of the compounds or composition