a 57-year - old woman was admitted to our hospital for further evaluation of a mass located in the upper abdomen , and this mass was incidentally detected by an abdominal ultrasound exam during a medical checkup .
the patient presented with recurrent abdominal distension without any other complaints . her medical history was unremarkable except for cholecystolithiasis and a fatty liver that were diagnosed two years previously . on admission ,
the laboratory tests showed an extremely high level of -fetoprotein ( afp ) > 35,350 ng / ml ( reference : < 20 ng / ml ) . the carbohydrate antigen ( ca ) 19 - 9 , ca125 ,
blood amylase , aspartate transferase ( ast ) , alanine transferase ( alt ) and bilirubin levels were within the normal ranges .
pre - contrast and contrast - enhanced spiral ct of the abdomen was performed , including the arterial phase , portal venous phase and equilibrium phase following bolus injection of intravenous contrast material .
the pre - contrast ct scan revealed a 4.5 cm in diameter , smooth - marginated , solitary , heterogeneous mass occupying the pancreatic neck and body ( fig .
two hypodense lesions were discovered in the liver and they measured 4.7  4.3 cm and 7.0  6.8 cm , respectively , displaying minimal diffuse heterogeneous enhancement ( fig .
the high density within the large mass in the left hepatic lobe indicated central hemorrhage . since pancreatic cancer is sometimes associated with an elevated afp level ( although not so high as in this patient ) and more often the hepatic metastases , an initial diagnosis of conventional pancreatic adenocarcinoma was made .
the patient underwent neoadjuvant chemotherapy that consisted of fluorouracil , tetrahydrofolate and cisplatin , yet this had little effect and the serum afp level did not decrease .
an encapsulated mass measuring about 4 cm in diameter was discovered in the pancreatic neck and body .
in addition , two metastatic lesions 5.0  4.0 cm and 4.0  3.0 cm in size , were found in the iii , iv and vii hepatic segments .
tumor resection that included the primary pancreatic neoplasm and the right hepatic metastatic mass was carried out .
for the left hepatic mass , hepatic segmentectomy ( segments ii and iii and part of segment iv ) was performed .
the immunohistochemical examination demonstrated that the tumor cells were diffusely positive for afp , placental alkaline phosphatase ( plap ) and carcino - embryonic antigen ( cea ) , but they were negative for ca19 - 9 .
the afp level was notably decreased after surgery ( 2,097 , > 1,200 , > 500 ng / ml on the postoperative 3rd , 9th and 25th day , respectively ) . to exclude the existence of primary gonadal germ cell tumor , further clinical and ultrasound examinations were conducted on the genital system of this patient , but no abnormality was found . a month after the operation ,
the patient received systematic chemotherapy with the bep regimen ( bleomycin , etoposide and cisplatin ) .
a total of three cycles of therapy were performed with an interval of three weeks between cycles . during chemotherapy , the ct examination was repeated and it revealed no tumor recurrence in the pancreas .
of all the genital tumors , yolk sac tumors are relatively uncommon and they are mostly discovered in infants and adolescents ( median age , 19 years ) ( 3 ) . although they typically arise from the gonads , ysts have already been reported in many extragonadal sites . generally , the mediastinum , the sacrococcygeal region , the brain , the retroperitoneal space and the female reproductive tract are relatively common locations .
exceedingly rare sites such as liver , kidney , omentum , stomach , spinal cord , etc have also been previously reported ( 4 - 6 ) . to the best of our knowledge , there has been no report about primary yst arising in the pancreas , and especially occurring in a 57-year - old woman .
because of their rarity , there has been no systematic study on the ct features of extragonadal ysts with a large number of cases . in a previous case report
, this tumor was usually described as a large , multi - lobulated , solid heterogeneous , hypodense mass that showed moderate and heterogeneous enhancement ( 7 ) .
central necrotic and/or cystic changes were observed on the ct images by wong et al .
choi et al . ( 9 ) evaluated the ct findings of ysts of the ovary in ten patients , and they characterized these tumors as large , smooth - marginated , well enhancing , solid masses with a cystic , hemorrhagic or necrotic portion . in the present case , the non - contrast ct scan showed an oval - shaped , heterogeneous soft - tissue mass with a central hypodense area , and the mass displayed moderate inhomogeneous enhancement .
the imaging findings were verified by the morphological observations of an encapsulated tumor with focal necrosis .
central hemorrhage was detected in the hepatic metastatic lesion , which might be attributed to the notable proliferative and vascularization activities of the tumor cells . in some studies
, ysts have shown infiltrative growth into the adjacent soft tissues , and higher magnification revealed a microcystic growth pattern of tumor cells that formed reticular or glandular structures , which contributed to the cystic or necrotic changes seen on the ct images .
since ysts usually show high malignancy , the duration from the onset of symptoms to the admission is always short and metastasis may already exist at the time of the patient 's admission , like the case presented here .
an extremely high afp level may be a clue for making the diagnosis of ysts .
because of the extreme rarity of primary yst of the pancreas , metastatic germ cell tumor from the gonads or other primary or metastatic pancreatic neoplasms should be excluded .
, we present here the first case of primary yst arising in the pancreas with hepatic metastasis in an adult woman .
this unique case is of value for reminding radiologists and oncologists to be aware of the diagnosis of yst when a patient presents with an extremely high level of afp and an oval - shaped or multilobulated , heterogeneous , soft tissue mass is discovered in the pancreas displaying moderate and inhomogeneous enhancement on ct images . making a careful differential diagnosis
 extragonadal yolk sac tumor ( yst ) is a relatively rare entity . 
 we describe here the case of an extragonadal yst that occurred in the pancreas with hepatic metastasis in an adult woman . 
 the contrast enhanced ct images of the abdomen revealed a heterogeneous , solitary mass occupying the pancreatic neck and body with slightly inhomogeneous contrast enhancement . 
 two low - density lesions in the liver were also displayed on the ct images . 
 the patient underwent surgery and the diagnosis of yst was pathologically verified . 
CASE REPORT
DISCUSSION