Figure 4: Immunohistochemical expression of somatostatin receptors (SSTR) in tumor cells. SSTR2A has a predominantly cell membrane staining (a), as also observed in a control pancreatic islet (a, inset). Conversely, somatostatin receptor subtypes SSTR3 (b) and SSTR5 (c) have a weak diffuse or finely granular cytoplasmic reactivity in the majority of neoplastic cells [magnification 400x (a) and 200x (b, c and insert of a).