SSTR2 and pancreatic insulinoma: In the cases of insulinomas [180], SSTR2 is the most commonly expressed receptor, although SSTR3 generally correlates with a larger tumor size and SSTR3 and SSTR5 co-expression correlates with a less positive outcome; in general, SSTR expression in insulinomas is weak, with about 20% of such tumors not expressing SSTRs at all [181].