neuroendocrine tumors of the lung include atypical and typical carcinoids , large cell neuroendocrine carcinomas and small cell lung carcinomas .
typical carcinoids ( tcs ) and atypical carcinoids ( acs ) of the lung have rapidly increased in the last 30 years with an incidence of 1.57/100.000 in 2003 .
tcs are often regarded as benign due to their low proliferation rate ( ki-67 < 2% ) .
the treatment of choice is surgery , which can be curative in most cases . although tcs share histologic features with gastroenteropancreatic neuroendocrine tumors ( gep - nets ) , they exhibit a lower tendency to form secondary tumors .
tcs express thyroid transcription factor-1 ( ttf-1 ) and cd56 , whereas gep - nets do not .
despite their low proliferation rate , tcs may recur and metastasize . currently , there are no specific guidelines for preoperative staging or follow - up of typical lung carcinoids
. follow - up of these patients is often individualized and somatostatin receptor ( sstr ) based positron emission tomography ( pet)/computed tomography ( ct ) is rarely performed .
bronchoscopy was normal . preceding surgery , a [ f]fluorodeoxyglucose ( fdg)-pet / ct scan was performed as recommended for staging of pulmonary tumors .
figure 1(a ) [ f]fdg pet / ct located a tumor with low glucose uptake in the lingula . ( b ) [ ga]sstr - pet / ct detected somatostatin receptor positive lesions in the terminal ileum and peripancreatically . 

( a ) [ f]fdg pet / ct located a tumor with low glucose uptake in the lingula .
( b ) [ ga]sstr - pet / ct detected somatostatin receptor positive lesions in the terminal ileum and peripancreatically .
pathology demonstrated a 12  mm typical carcinoid ( ki-67 < 5% , see fig .
none of the lymph nodes removed were invaded ; the final staging was pt1 pn0 cm0 .
after surgery , follow - up was performed every 3 months by ct of the chest .
it was noted that tumor marker chromogranin a was increasing in december 2010 and the patient was complaining about recurrent abdominal pain .
sstr - pet / ct with [ ga]dota - tyr3-octreotide pet / ct ( [ ga]dotatoc ) was performed and demonstrated a tumor in the terminal ileum associated with an enlarged parapancreatic lymph node ( fig .
a radical right hemicolectomy encompassing lymphadenectomy was performed in february 2011 , using gamma probe detection after [ ga]dotatoc was given as tracer .
pathology revealed a well - differentiated net from the ileocecal valve ( size 10  mm , fig .
the final union for international cancer control ( uicc ) staging was pt2 , pn1 , pm0 , g1 , l0 , v0 , r0 , pn0 .
4c ) , somatostatin receptor 2a and cdx-2 , but negative for ttf1 ( fig .
5c ) indicating an intestinal origin without any relation to the tc removed 4 years earlier . 

( d ) ttf-1 : lung . ( a ) net of the ileum ( 1.0  cm ) after ileotomy .
this case report describes the occurrence of two non - related well - differentiated nets in a single patient detected within 4 years .
the first net demonstrated pathologic features of a pulmonary tc and the second , also a well - differentiated net , originated from the ileocecal valve .
the intraoperative exertion of a gamma probe often results in the extension of the planned surgical procedure , especially in an extended lymph node resection .
it permits the identification of previously occult metastases and the localization of hidden lymphatic lesions .
although little is known about development of second nets in patients without multiple endocrine neoplasia syndromes , follow - up of patients with nets using sstr - pet / ct will help in the detection of tumor recurrence or other non - related nets . in our patient ,
the second net was only detected by a somatostatin receptor pet / ct 4 years after curative surgery of the tc of the left lung .
5a ) , it can be assumed that this tumor was already present in 2007 , however [ f]fdg / pet usually does not detect gep - nets with a low proliferation rate . in our case , after removal , we performed only local staging using thorax ct and bronchoscopy .
if the net diagnosis is discovered after surgery , similar to gep - nets , systemic molecular imaging ( [ ga]sstr - pet / ct or octreotide scintigraphy ) must be performed postoperatively .
this rules out occult metastases and provides reference imaging for further comparative follow - up studies . however , because of the limited availability of this molecular imaging technique , it does not allow routine staging after surgery . in our opinion , this imaging procedure should be reserved for when increasing levels of biomarkers or clinical symptoms indicate a recurrence .
if the net diagnosis is known or presumed preoperatively , accurate preoperative staging and a postoperative comparative study from the resection results are enabled through this imaging technique .
this case report illustrates the clinical utility of sstr - pet / ct for the detection and follow - up of patients with nets of the lung and gastroenteropancreatic system .
 abstractwell - differentiated neuroendocrine tumors ( nets ) of the lung occur as typical and atypical carcinoids . 
 little is known about the biology of these tumors in respect of their ability to metastasize or the probability of development of concomitant neuroendocrine tumors . here 
 we report a patient diagnosed with a second neuroendocrine tumor of the ileum 4 years after curative resection of a typical carcinoid of the left lung . 
 the intestinal neuroendocrine tumor was successfully detected by gallium-68 based somatostatin receptor positron emission tomography ( pet)/computed tomography ( ct ) and surgically removed using gamma probe detection based on the same labeling . 
 this case report underlines the utility of somatostatin receptor pet / ct based detection and follow - up of nets . 
Introduction
Case report
Discussion