a solid pseudopapillary tumor ( spt ) is a relatively uncommon neoplasm of the pancreas with a relatively high prevalence in young women ( 1 ) . most spts are limited to the pancreas , and an adequate surgical intervention results in long term survival ( 2 - 4 ) . the natural course of spt has not yet been clarified due to a lack of reports based on a long follow - up period . recently , a few case reports have described natural reduction of spt in pediatric patients ( 6 - 8 ) ; however , the tumors in those cases were confined to the pancreas and were relatively small ( less than 5 cm ) . we herein report on an unusual case of a large spt with liver metastases in which the tumor showed a marked decrease in size from 11 to 3 cm and demonstrated a complete disappearance of hepatic metastases over a period of 13 years without any relevant treatment . to the best of our knowledge , this is the first report describing the spontaneous shrinkage of spt and the disappearance of distant metastasis . a 14-year - old boy presented with continuous upper abdominal pain after falling down . physical examination revealed a soft , flat abdomen with no palpable mass or tenderness , and no enlargement of the superficial lymph nodes . laboratory data upon admission showed no abnormalities in serum hormone levels , including those of insulin , glucagon , gastrin , secretin , and vasoactive intestinal peptide . the same is true for levels of tumor markers , including those of carbohydrate antigen 19 - 9 and carcinoembryonic antigen . 1a , b ) demonstrated an encapsulated mass measuring 11  10 cm , and located in the left upper quadrant . the portal vein , stomach , and the body of the pancreas were displaced anteriorly , while the celiac axis was displaced upward , and the left kidney was displaced posteriorly . the tail of the pancreas was not delineated , suggesting that the mass originated from the pancreatic tail . no involvement of the bile duct or the portal vein and no enlarged lymph node were observed . in the right hepatic lobe , there were three masses with maximum diameters of 6.0 cm , 5.3 cm , and 3.5 cm , respectively . ultrasound - guided percutaneous biopsy of the pancreatic mass revealed " a solid and cystic pseudopapillary neoplasm " . clinicians planned a tumor resection and the right hemi - hepatectomy and right portal vein embolization was performed for induction of left hepatic hypertrophy . however , the patient and his family refused surgery and was subsequently lost to follow - up . five years later , the patient visited our hospital in order to obtain a medical certificate . 1c , d ) showed that the tumor had decreased in size from 11 to 4.5 cm and contained foci of calcification . the hepatic masses had almost disappeared , and only one 2-cm mass remained at the right hepatic dome . during the five - year period the last follow - up ct , which was performed 13 years later ( fig . 1e , f ) , showed that the size of the pancreatic mass was 3 cm and that the residual hepatic mass had completely disappeared . presently , the patient is doing well and will continue with follow - ups in our hospital . solid - pseudopapillary tumor is an uncommon neoplasm of the pancreas , accounting for 1 - 2% of all exocrine pancreatic tumors , and usually occurs in young females in their second or third decade of life ( 1 , 9 ) . most cases of spt of the pancreas are limited to the pancreas and cured by complete resection ( 2 - 4 ) . thus , surgical resection has been considered the treatment of choice . of all spts , approximately 6% were reported to invade surrounding organs and approximately 10 - 15% developed distant metastasis . typically , ct shows a well - encapsulated heterogeneous mass in the pancreas with both solid and cystic components as in our case ( 10 ) . thus , when these features are encountered in a young female patient , this neoplasm should be a strong diagnostic consideration . to the best of our knowledge , there have been three articles regarding spontaneous regression of spts of the pancreas and the patients were all pediatric patients . ( 6 ) reported a case showing shrinkage of a tumor from 4.5 cm to 1.5 cm during a 10-year follow - up period , and suzuki et al . ( 7 ) reported on a case showing shrinkage of a tumor from 5 cm to a non - measurable size over a six - year period . also , hachiya et al . ( 8) demonstrated two cases of vanishing spts measuring 3 cm and 4 cm , respectively on long term follow - up . the authors explained that the natural shrinkage resulted from degenerative change , including hemorrhage and necrosis , followed by absorption . spts of these cases were primary pancreatic masses , which were relatively small ( less than 5 cm ) . in our case , both the primary tumor and the three hepatic masses were large . to the best of our knowledge , this is the first case report of the natural regression of a large spt and multiple distant metastases . the patient did not undergo any relevant treatment during the follow - up period except for right portal vein embolization for induction of left hepatic lobe hypertrophy . because the tumors were hypovascular , as shown by minimally enhancing tumors on contrast - enhanced ct and no tumor staining on angiography , we do not think that the portal vein embolization had an effect on shrinkage of the hepatic tumors . in a previous similar case report , the authors underwent portal vein embolization for delayed hemihepatectomy as in our case and a 3-month follow - up ct showed no shrinkage of hepatic metastases ( 11 ) . although it was a relatively short - term follow - up , this report is supporting our speculation that the portal vein embolization was not impacted on the tumor regression . therefore , in the present case , we believe that regression of the primary and metastatic tumors should be considered spontaneous . given the paucity of the reported cases , the management of metastatic disease is , to date , poorly defined . vollmer et al . ( 11 ) reported a case with a pancreatic spt with liver metastases in an adult patient and the case was managed by aggressive surgical treatment due to an indeterminate pathology . in fact , because surgical resection for even solitary pancreatic spt has been recommended considering the possibility of malignant potential ( 2 - 4 ) , their management could be acceptable . however , under the absence of established treatment guidelines in the pediatric patient , the clinical course of the patients in this case report indicates that spts are histopathologically - confirmed , especially in pediatric patients . also , when some tumor regression is observed , a " wait and see " strategy is worth a try to avoid unnecessary surgery .
a solid - pseudopapillary tumor ( spt ) of the pancreas is known as a low grade malignant tumor with a good prognosis ; therefore , surgical intervention is necessary . a 14-year - old boy presented with a large pancreatic spt and three hepatic metastases . 
 the patient and his family refused surgery . 
 two serial follow - up ct scans over a period of 13 years demonstrated almost complete disappearance of the pancreatic tumor and three hepatic metastases without relevant treatment . 
 although there have been a few reports of spontaneous healing of spt , there has been no report regarding spontaneous disappearance of spt and distant metastasis . 
 herein , we report on the spontaneous regression of a large spt and the disappearance of three hepatic metastases .