Use of cyanine dyes for the diagnosis of proliferative diseases

Disclosed is the use of a compound according to formula (I) or a pharmaceutically acceptable salt thereof, for the preparation of a diagnostic composition for the detection of a proliferative disease (such as a tumor, a precancerosis, a dysplasia, a metaplasia. psoriasis, psoriatic arthritis, rheumatoid arthritis, endometriosis and/or an ocular disease), wherein the proliferative disease is related to detectable proliferative lesion having a diameter smaller than 7mm, wherein the diagnostic composition comprises the compound in an amount of less than 0.5 and more than 0.001 mg/kg body weight per diagnostic application.