Thin agarose sections (20 μm) of tumours expressing high and low HER2 levels, BT474 and MDA-MB-231, show HER2 in green fluorescence, stained with the anti-HER2 polyclonal antibody NeuC-18 (pAb-HER2) in combination either with a secondary antibody labelled by Alexa Fluor (AF)−546 (pAb-HER2-AF) or with sdAb-HER2-QDs nanoprobes (Fig. 2). Here, ERBB2 is linked to neoplasm.