RASSF1 and pancreatic neuroendocrine tumor: Likewise, high frequency of RASSF1A inactivation is observed in tumor types with uncommon ras gene mutations, including small cell lung cancer, nasopharyngeal cancer and neuroendocrine pancreatic tumor [31], [32], [33] These observations suggest that the occurrence of frequent RASSF1A inactivation may exclude the necessity of K-ras activation to alter Ras signaling in carcinogenesis.