A 70-year-old man was referred to our hospital for examination of a pancreatic cyst with a solid component suspected as IPMN. EUS revealed a spherical cystic lesion with a low-echoic solid component. CT scan revealed a pancreatic cyst with contrast effect at the margin and a solid component. The images suggested solid tumors with cystic degeneration, such as PNET. Under the tentative diagnosis of PNET, pancreatoduodenectomy was performed. Histologically, the tumor was diagnosed as NET G1 (WHO classification 2010) . Although most PNET are recognized as solid tumors, it was reported that 17% of the PNET had cystic degeneration. When cystic lesions are found in the pancreas, cystic degeneration of solid tumors such as PNET as well as cystic tumors such as IPMN must be differentiated.
