they occur in approximately 1 in 100,000 or represent 12% of all pancreatic neoplasms . some of the tumors may be part of the multiple endocrine neoplasia type one syndrome ( men-1 ) . etps are categorized on the basis of their clinical manifestation into functioning and nonfunctioning tumors . functioning tumors are associated with a clinical syndrome caused by inappropriate secretion of hormones . within this group are insulinomas , glucagonomas , somatostatinomas , gastrinomas , vasoactive intestinal polypeptide producing tumors ( vipomas ) and other less common tumors . it has also been called verner - morrison syndrome , pancreatic cholera or wdha ( watery diarrhea / hypokalemia / achlorhydria ) syndrome . this syndrome is characterized by secretory diarrhea which ranges between 0.5 and 15 l/24 h and which is usually the most prominent symptom at presentation . it results in severe loss of potassium and bicarbonate , which in turn lead to metabolic acidosis and dehydration . additional features include hypercalcemia with normal parathyroid hormone levels , hyperglycemia , and occasionally flushing of the face and the chest . the diagnosis of a vipoma is confirmed by measurement of plasma vip , and levels above 60 nonfunctioning etps are not associated with a distinct hormonal syndrome , but may still show elevated hormone levels in the blood or immunoreactivity in tissue sections . the majority of nonfunctioning etps express and/or secrete pancreatic polypeptide ( pp ) , which can therefore serve as a general tumor marker in etps . pp was discovered in 1968 , when kimmel and colleagues , while purifying chicken insulin , found a new peptide hormone which they named first , cases of pure pp - producing tumors , so - called ppomas ; second , mixed etps containing pp cells ; and third , cases of pp cell hyperplasia . although pp frequently occurs in patients with etps , elevated serum levels of pp were not connected with specific clinical symptoms . herein , we report only the fifth case of the world literature with a pure ppoma of the pancreatic head causing wdha syndrome . a 46-year - old woman was admitted to our hospital because of a 2-year history of diarrhea . one month prior to admission , she had undergone ct imaging of the abdomen , which showed a pancreatic head tumor , 4.2  3.3 cm in size ( fig . her medical history revealed an appendectomy as a child and a benign cyst of the right breast . on admission , physical examination revealed a thin woman in no acute distress . determination of peptide hormones in the serum showed greatly increased concentrations of pp with 4,370 pg / ml ( normal up to 80 pg / ml ) . surprisingly serum levels of vip were normal with 8.5 pmol / l ( norm up to 36 pmol / l ) , the same was found for gastrin with levels of 12 pg / ml ( norm up to 60 pg / ml ) . abdominal ultrasound showed a hypoechoic tumor in the pancreatic head 4.8  3.6  3.2 cm in size . her serum pp level after removal of the tumor was 55 pg / ml and was completely suppressed by 1 mg intravenous atropine . after a follow - up of three years she remained well without any watery diarrhea or any other signs of tumor recurrence . 2b ) in diameter , with a weight of 12 g. microscopically the neoplasm was an endocrine tumor , proven by a strong expression of chromogranin a ( fig . 2c ) it had a well - defined capsule and was made up of small cuboidal to slightly elongated cells with round nuclei and clear to eosinophilic cytoplasm . the tumor cells were arranged in various patterns , a characteristic feature of islet cell tumors . results of immunohistochemical staining specific for insulin , glucagons , somatostatin , and gastrin were negative . 2b ) in diameter , with a weight of 12 g. microscopically the neoplasm was an endocrine tumor , proven by a strong expression of chromogranin a ( fig . it had a well - defined capsule and was made up of small cuboidal to slightly elongated cells with round nuclei and clear to eosinophilic cytoplasm . the tumor cells were arranged in various patterns , a characteristic feature of islet cell tumors . results of immunohistochemical staining specific for insulin , glucagons , somatostatin , and gastrin were negative . however , staining for pp was positive in the main tumor mass ( fig . in mammals , virtually all of the pp - producing cells are located in the pancreas . they have been found within the islets , scattered in the exocrine compartment , and lining the ducts . within the islets the pp cells are located mainly in the periphery , wedged between the a and b cells . pp islet cells are relatively abundant in both the murine ventral and dorsal pancreatic buds by day 15.5 of gestation . subsequently , at day 18.5 of gestation , the total number of pp cells in the murine ventral bud has doubled , whereas the number in the murine dorsal bud has essentially remained unchanged . this nonhomogenous distribution of pp cells can also be seen in the human neonate . indeed , pp cells are more numerous in the uncinate process than in the body and tail and rest of the pancreatic head . infusions of pp in man demonstrate that , at physiological levels , it acts solely on the pancreas and gallbladder by inhibiting the secretion of bile and of pancreatic enzymes and juice . that is this not always the case as illustrated in this case and table 1 . in 1979 , there was still controversy about how often wdha syndrome , with a causal pancreatic tumor , is mediated by excessive secretion of vip . although elevated vip serum levels were measured in the majority of patients , there have been reports about so - called pseudo - verner - morrison syndromes with a clinical wdha syndrome in the presence of normal vip serum levels . were the first to report on a patient with diarrhea due to a pancreatic tumor in whom pp was markedly elevated in the plasma with normal levels of vip in the plasma . in 1980 four years later , strodel et al . published a series of eight patients with pp - producing islet cell tumors . two patients presented with diarrhea , but in only one of them a pancreatic tumor was found and resected . the last report came from mortenson and bold . they described a 64-year - old woman who presented with watery diarrhea in the presence of men-1 syndrome . of various potential pancreatic endocrine hormones , only serum levels of pp were elevated . radiologic imaging failed to identify a pancreatic tumor ; her diarrhea was therefore managed with subcutaneous administration of somatostatin . three years later she developed gallstone pancreatitis with the subsequent development of a pancreatic pseudocyst . at exploration for drainage of the pseudocyst , final pathology documented a pancreatic endocrine tumor with immunohistochemical staining demonstrating the presence of pp . beside these four cases , there have been multiple case reports about ppomas , excluded from table 1 because either of lacking wdha syndrome or because no real circumscribed pancreatic tumor could be identified [ 9 , 10 ] . as shown in table 1 , the normal serum level of vip and the elevated serum level of pp suggest that the symptoms in our patient seem to be derived from the high levels of circulating pp . a correlation between the serum pp concentrations and the wdha syndrome could be demonstrated by absence of the syndrome after removal of the tumor due to an immediate fall in serum pp . preoperatively us , ct scan or endoscopic ultrasound are the procedures of choice and are usually effective , because these tumors are relatively large [ 11 , 12 ] . also srs can be performed to differentiate endocrine from nonendocrine pancreatic tumors . recognition of etps is imperative because of their good resectability and excellent long - term survival compared to that of ductal pancreatic carcinoma [ 13 , 14 ] . this may require partial pancreatoduodenectomy in large tumors with local signs of malignancy or enucleation like in the present case . some years ago , jensen described eight different neoplastic disorders that can cause chronic diarrhea . this list included gastrinomas , vipomas , glucagonomas , somatostatinomas , and calcitonin - producing tumors . the present case suggests that , although rare , ppomas have to be added to this list .