insulinoma is a rare neuroendocrine tumor of the pancreas , accounting for 2% of all pancreatic tumors . its occurrence is 1:100,000 and it is more common in women over 50 years of age . insulinomas are usually solitary benign tumors , and less than 10% of them are malignant2,3 ) . malignant insulinomas are diagnosed when metastases occur , but distinguishing malignant insulinomas from benign insulinomas is difficult histologically . focal nodular hyperplasia ( fnh ) represents a localized liver cell hyperplasia containing central and/or stellate fibrous scar4 ) . children account for only 7% of cases of this tumor , and fnh comprises only 2% of all pediatric liver tumors5,6 ) . we report a case of an insulinoma in an 11-year - old child who subsequently developed multifocal nodular lesions of the liver after resections of the insulinoma . an 11-year - old girl was admitted for evaluation of recurrent seizures that had begun 5 months before admittance , especially in the morning , despite administration of oral antiepileptic medication . although brain magnetic resonance imaging ( mri ) and electroencephalogram studies were all normal 2 months before admittance , she again had a seizure and was prescribed with oral levetiracetam to control her seizure attacks . ten days prior to admittance , the patient had been brought to the emergency department due to an ongoing seizure . her serum glucose level was 35 mg / dl and she was controlled seizure by intravenous infusion of 10% dextrose fluids . after discharge , she experienced 3 additional attacks of seizures that had been relieved by grape juice . upon admittance , her height was 161.3 cm ( > 97th percentile ) , and her weight was 47.6 kg ( 75th < percentile<90th ) and her body mass index was 18.8 kg / m ( 50th < percentile<75th ) . all vital signs and the physical characteristics of the organs were all normal . initial laboratory results , including a serum glucose level of 104 mg / dl , were unremarkable . a 72-hour fast test was initiated , and the patient demonstrated drowsiness , trembling , and tachycardia after less than 6 hours . laboratory test results during the fast period showed hyperinsulinemic hypoglycemia without ketonuria : the serum insulin level was 50.1 u / ml ( normal range , 2.0 - 25.0 u / ml ) , serum c - peptide level was 1.81 ng / ml ( 0.59 - 1.56 ng / ml ) , and plasma glucose level was 21 mg / dl ( 70 - 100 mg / dl ) . subsequent glucagon stimulation test results revealed an increase in insulin level to 85.8 u / ml . the mri studies revealed a solid mass , 3 cm2.4 cm in size , with lobulated margins , in the pancreatic tail ( fig . 1 ) , with no metastasis , while abdominal ultrasonography ( us ) and computed tomography ( ct ) results were normal . the tumor was easily detected due to its superficial position at the end of the pancreatic tail , and no enlarged lymph nodes were detected around the pancreas or metastatic lesions in the abdominal cavity . the pathologic examination indicated that the resected tumor ( 3 cm3 cm2.5 cm in size ) was multilobulated and not encapsulated , and no necrosis was evident . the tumor was of neuroendocrine origin , well differentiated , with an intermediate grade ( mitoses 4/10 high - power fields ) with angioinvasion . the ki-67 index , a cellular marker for proliferation which < 3% means a low grade tumor , was 1% ( fig . , fasting serum glucose levels were maintained between 110 to 140 mg / dl without any treatment . follow - up mri studies were conducted 2 months after tumor removal , and revealed multiple hypointense nodular lesions in the hepatic segments s5 , s6 , and s8 ( fig . us - guided needle biopsy of the liver yielded a diagnosis of the lesions as fnh , with no necrosis or mitotic activity was noted . since then the patient has been free of hypoglycemia for 2 years , and there was not the learning problem in her school . recent mri studies have shown that the fnh lesions have decreased in size , without any evidence of metastasis . the classical diagnosis of insulinomas is based on whipple 's triad : hypoglycemia of serum glucose lower than 50 mg / dl , neuroglycopenic symptoms ( such as behavioral or personality changes and seizure ) , and prompt alleviation of symptoms after administering glucose . malignant insulinoma is extremely rare in the pediatric population , with only a few cases reported in the english literature . distinctions between benign and malignant insulinomas are based on metastasis or the invasion of the primary tumor into the lymph nodes , tissues , or other organs8 ) . insulinomas larger than 3 cm are also more likely be malignant , with local invasion or metastases to the liver9 ) . recently , janem et al.3 ) reported a pediatric case of malignant insulinoma in the context of a literature review of 9 preceding cases . among the nine cases , five cases showed liver metastasis , two cases showed capsular invasion , and data for the remaining two cases were not available . considering the criteria of malignant insulinoma , which require metastasis or local invasion of adjacent lymph nodes or tissues , these five cases with liver metastasis - together with the case reported by janem et al.3 ) involving metastasis to the liver , bone , and bone marrow - may be the only true reported malignant insulinomas to date . however , sata et al.10 ) and janez11 ) reported cases of malignant insulinomas initially diagnosed as benign , that recurred as liver metastases 8 and 15 years , respectively , after initial removal . neither of these studies confirmed metastasis or invasion during the initial surgery or in subsequent histologic exams of the initial specimens . thus , insulinomas may be considered as tentatively malignant because these rare tumors have unpredictable features and progression through the body . neuroendocrine tumors have recently been identified as risk factors that are strongly associated with aggressive tumor behavior leading to malignancy12 ) . histopathologic grading of tumor cells based on mitosis may aid in prediction of future insulinoma outcomes , as the biologic behavior of low - grade tumors is often rather nonaggressive , whereas high - grade tumors are very aggressive12 ) . our histopathologic findings showed a well - differentiated , intermediate neuroendocrine tumor of the resected insulinoma and our operation field findings revealed no evidence of metastasis . nevertheless , the possibility of malignancy was included due to the size of the tumor and its histological angioinvasion . the unusual multifocal hepatic lesions following tumor removal it has been infrequently documented in adults and children following chemotherapy , radiotherapy , and stem cell transplantation for different types of solid tumors13 ) . the cause is unknown , although one hypothesis is that obstruction of hepatic vessels or abnormal vascularization could account for fnh , as suggested by the reported association with clinical and anatomic findings like hypoplasia or agenesis of the portal vein , vascular malformations , hemangioma and vascular dysplasia , budd - chiari syndrome , and hereditary hemorrhagic telangiectasia14 ) . although ct and mri findings of fnh may commonly include the presence of a central scar and typical enhancement patterns , biopsy is necessary in difficult cases with differential diagnosis of liver adenomas and carcinomas . treatment recommendations regarding fnh are based on longitudinal follow - up of a small series of patients . because fnh is a benign tumor with rare complications , most lesions are followed nonoperatively with serial us or mri , provided that a reliable diagnosis can be achieved using radiologic imaging3,15 ) . hepatic lesions can induce diagnostic problems when metastasis must be ruled out . in our case , hepatic nodular lesions were identified as fnh by needle biopsy , but the association of an insulinoma with the fnh after surgery remains unclear . to our knowledge , this is the first pediatric case report of an insulinoma in which diagnosis was confused due to newly discovered hepatic lesions after tumor resection . close observation and follow - up imaging studies are required in patients who show malignant potential on histopathologic findings .
insulinoma , which arises from insulin - producing pancreatic beta cells , is a rare tumor in children . 
 only 5%-10% of insulinomas are malignant and undergo metastasis . 
 we report a case of an 11-year - old girl who experienced hypoglycemia - related seizures induced by an insulinoma ; after resection of the primary tumor , she developed hepatic focal nodular hyperplasia ( fnh ) . 
 laboratory test results indicated marked hypoglycemia with hyperinsulinemia . abdominal ultrasonography ( us ) and computed tomography results were normal ; however , magnetic resonance imaging ( mri ) showed a solid mass in the pancreatic tail . 
 therefore , laparoscopic distal pancreatectomy was performed . 
 two months after the surgery , an abdominal mri revealed multiple nodular lesions in the liver . 
 an us - guided liver biopsy was then performed , and histological examination revealed fnh without necrosis or mitotic activity . 
 the patient has been free of hypoglycemia for 2 years , and recent mri studies showed a decrease in the size of fnh lesions , without any evidence of metastasis . 
 even though no metastatic lesions are noted on imaging , close observation and follow - up imaging studies are required in a child with insulinoma that has malignant potential on histopathologic findings .