The present invention relates to an immunoassay method for the detection of Chromogranin A (or fragment(s) thereof) comprising the steps of contacting a sample suspected of comprising Chromogranin A with a first antibody or an antigen-binding fragment or derivative thereof specific for Chromogranin A and a second antibody or an antigen-binding fragment or derivative thereof specific for Chromogranin A under conditions allowing for the formation of a ternary complex between Chromogranin A and the two antibodies or antigen-binding fragments or derivates thereof, and detecting the binding of the two antibodies or antigen-binding fragments or derivates thereof to Chromogranin A. Also provided are antibodies directed against amino acid residues 124 to 144 and 280 to 301 of Chromogranin A and their use in the immunoassay method.