there are two forms of autoimmune pancreatitis ( aip ) , type 1 is called  lymphoplasmocytic sclerosing pancreatitis and type 2 is the idiopathic duct - centric pancreatitis. aip type 1 seems to be a member of the  igg4-related group of diseases , associated with high serum level of igg4 gamma globulin fraction , igg4-positive plasma cell tissue infiltration and sclerosis [ 14 ] . a 60-year - old male is presented with abdominal pain . on ct scan , a 70  66 control imaging studies showed enlargement of the mass , infiltrative growth , venous compression and appearance of a pathologic lymph node , suggesting a malignant process , therefore we decided surgical exploration ( fig .  1 ) . a solid , malignantly appearing lesion was identified in the body and tail of the pancreas , infiltrating the splenic hilum and transverse colon . a pylorus - preserving total pancreatectomy with splenectomy and extended right hemicolectomy was performed with an uneventful postoperative recovery ( fig .  2 ) . ( a ) the pancreatic mass in the tale of the pancreas , the arrows shows the relationship to the colon , to the spleen and to the splenic artery and ( b ) the pancreatic mass in the head of the pancreas . figure  2:macroscopic specimen ( two separate pancreatic mass in the head and in the tale of the pancreas + duodenum + colon + spleen ) . ( a ) the pancreatic mass in the tale of the pancreas , the arrows shows the relationship to the colon , to the spleen and to the splenic artery and ( b ) the pancreatic mass in the head of the pancreas . macroscopic specimen ( two separate pancreatic mass in the head and in the tale of the pancreas + duodenum + colon + spleen ) . on histological examination , both lesions contained elongated spindle cells , infiltration of plasma cells , lymphocytes , histiocytes and eosinophilic granulocytes . large number of plasma cells were igg positive , and 40% of the cells were igg4 positive ( fig .  3 ) . figure  3:histopathologic examination of the pancreatic mass : ( a ) he and ( b ) igg4 immunohistochemistry . histopathologic examination of the pancreatic mass : ( a ) he and ( b ) igg4 immunohistochemistry . the question arises whether it is possible to reduce the number of unnecessary operations , since aip can be treated with steroids [ 57 ] . endoscopic retrograde cholangiopancreatography ( ercp ) images can be so characteristic , which combined with any other positive test result can confirm the diagnosis of aip . our patient had no jaundice , so the indication for preoperative ercp was not self - evident  perhaps this test could have brought us closer to the diagnosis . ct , mri or magnetic resonance cholangiopanreatography ( mrcp ) can also show typical signs ( sausage - like broadening , infiltration of adipose tissue , ring - like delayed contrast enhancement and altering density distribution ) , but alone none of the tests is sufficient to verify the diagnosis . transabdominal or endoscopic ultrasound - guided pancreatic fine needle aspiration biopsy ( fnab ) is a valuable method detecting pancreatic cancer . however , a negative cytological finding does not exclude pancreatic cancer . whenever aip is suspected , eus  fnab or core biopsy is recommended , and alone the positivity of this test is sufficient for making the diagnosis . demonstrating v - ki - ras2 kirsten rat sarcoma viral oncogene homolog ( kras ) mutations from the fnab sample further helps to distinguish aip for malignant pancreatic disease , since kras mutation is found in 90% of patients with pancreatic cancer , but never in aip [ 8 , 9 ] . the serum igg4 level can be elevated up to 7090% in aip type 1 ; however , 10% of pancreatic cancers can present with an increased igg4 . elevated ca 19 - 9 level is typical for ductal pancreas adenocarcinoma ; however , a slight increase of ca 19 - 9 levels can be observed in 20% of aip patients as well , but rarely elevated above 200 u / ml [ 7 , 10 ] . if this disease is suspected , a so - called  steroid trial might be used . however , patients with pancreatic cancer can also experience a lessening of their complaints ; therefore , this  trial could be used only by patients with tumor - negative core biopsies , in specialized centers when other aip - specific criteria are present . focal lesions of the pancreas should always be considered as malignant , unless other disease can not be unequivocally verified . on the other hand , retrospectively analyzing this case , we came to the conclusion that even in the case of a pancreatic lesion described by the imaging studies as clearly malignant , a possibility of a rare disease such as aip should be taken into consideration . all authors contributed to the design and interpretation of the study and to further drafts . no benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article .
autoimmune pancreatitis ( aip ) is a rare disease of unknown pathomechanism . 
 it belongs to the igg4-related disease family and responds well to steroids , although the relapse rate can reach up to 2030% . 
 differentiating aip from the more common pancreatic cancer can be very challenging . about 20% of aip 
 is diagnosed postoperatively during final histological examination . 
 each of the investigative tools can add something to the definitive diagnosis ; the question remains whether it is possible to prevent an unnecessary resection . through our case 
 we would like to demonstrate the differential diagnostic opportunities and present the literary background of this issue . in conclusion 
 , we can state that whenever a focal pancreatic lesion is encountered aip should always be considered .