The present invention relates to an in vitro process for the diagnosis of prostate cancer and other tumor types in exosomes obtained from a body fluid which comprises a) concentrating the exosomes and other extracellular vesicles from a body fluid of a patient, b) extraction of total RNA from the exosomes obtained in step a), c) conversion of the RNA obtained in step b) to cDNA, d) amplification of the cDNA obtained in step c) with a polymerase chain reaction whereby primers derived from the AGR2 nucleotide sequence or the complement thereof are used, and e) determining whether in the amplification product variants of the AGR2 gene can be identified.