the tumor produces catecholamines , such as norepinephrine and epinephrine , and leads to well - known clinical symptoms , such as hypertension , headache , sweating , palpitation , and orthostatic hypertension .
it is usually found at extra - adrenal sites and is diagnosed as a subtype of paraganglioma .
the high dopamine level in this tumor is caused by a deficiency in dopamine - beta - hydroxylase , which converts dopamine to norepinephrine .
for this reason , this tumor differs from classic pheochromocytomas in many respects , not only in its clinical features but also in its oncologic aspect .
only two original articles and five case reports have reported the occurrence of dopamine secreting paragangliomas in the retroperitoneum around the adrenal glands [ 2 - 8 ] .
we report this interesting case and establish clinical concepts for this rare tumor by reviewing the related literature .
a 26-year - old korean woman was referred after the accidental detection of an adrenal mass in her right side .
she had no hypertension , palpitation , sweating , headache , flank pain , or mass upon palpation of her abdomen . on physical examination ,
her blood pressure was 110/90 mmhg and her heart rate was 90 beats / min .
the results of laboratory tests , including a complete blood count and liver and renal function tests , were all unremarkable .
serum norepinephrine and epinephrine levels were normal but the dopamine level was high ( 425 ng / l ) .
analysis of a 24-hour urine sample revealed marked elevation of the urinary dopamine level ( 1,565.3 g / day ) but normal levels of vanillylmandelic acid ( vma ) , norepinephrine , epinephrine , metanephrine and normetanephrine . computed tomography results showed a 4.3  3.2 cm hypervascular mass on the right adrenal gland with an early washout enhancement pattern .
1 ) . magnetic resonance imaging revealed a 2.8 cm sized tumor that was located in the right periadrenal area and that abutted against the adrenal gland laterally and ivc medially ( fig .
2 ) . our preoperative diagnosis was a dopamine producing paraganglioma in the right retroperitoneum .
hand - assisted laparoscopic right adrenalectomy was performed because of the firm attachment of the tumor to adjacent structures .
her blood pressure was continuously normal and there were no fluctuations in vital signs during the operation .
it was well encapsulated , homogenous and had a yellowish cut - surface with some internal hemorrhagic spots .
microscopic diagnosis was a neuroendocrine tumor whose clinical manifestations were consistent with those of a paraganglioma .
an immunohistochemical study showed that the tumor was positive for neuroendocrine markers such as cd-56 , synaptophysin and chromogranin .
the tumor had a ki-67 index of less than 1 percent and was negative for s-100 ( fig .
her 24-hour urine dopamine level returned to normal ( 388.4 g / day ) after the operation .
her general condition was good and there was no recurrence during a 10-month follow - up .
among the many types of paraganglioma , an exclusively dopamine producing type is extremely rare .
only seven cases are listed in the worldwide database and no case has ever before been reported in south korea [ 2 - 8 ] .
the exclusive production of dopamine can be ascribed to a deficiency in dopamine -hydroxylase which converts dopamine to norepinephrine in the catecholamine biosynthesis pathway beginning with tyrosine .
because of the abnormal catecholamine synthesis pathway , the levels of dopamine and its end product , homovanillic acid ( hva ) , are increased , whereas the levels of norepinephrine , epinephrine and their end product , vma , are decreased . in consequence , the clinical presentation of this tumor is different from that of a classical pheochromocytoma that secretes norepinephrine and epinephrine .
there is an absence of hemodynamic changes or so - called paroxysmal symptoms that are usually found in patients with catecholamine secreting pheochromocytoma . as a result ,
the patients with exclusively dopamine producing paraganglioma are mostly asymptomatic at initial diagnosis . some constitutional symptoms such as fever , malaise , weight loss or diarrhea may occur as a result of the increased circulating dopamine level .
because paragangliomas tend to grow larger than adrenal pheochromocytomas , some patients experience vague abdominal pain or experience a palpable abdominal mass [ 4 - 8 ] .
the asymptomatic features make it difficult for clinicians to detect the tumor at an early stage .
detection is even more challenging to physicians working in institutes without routine screening procedures for the detection of catecholamine and dopamine .
differential diagnosis can be achieved by measuring the dopamine levels in serum and 24-hour urine samples .
clinicians should not rule out the possibility of this rare tumor when evaluating adrenal masses with normal serum norepinephrine , epinephrine and urinary vma levels , even if the radiologic images strongly suggest a pheochromocytoma .
hand - assisted laparoscopic surgery has been adapted for the removal of large tumors and for the rescue of operative procedures in complicated cases of laparoscopic surgery . to minimize surgical mortality caused by hypertensive crisis during the manipulation of
the tumor , preoperative administration of a -blocker is essential for norepinephrine and epinephrine producing pheochromocytomas .
however , -blocker treatment is contraindicated for exclusively dopamine secreting paraganglioma because it can cause profound cardiovascular collapse after surgery , and can even result in death following a hypotensive crisis .
there are two subtypes of dopamine receptors ; the d1 receptor , which relaxes smooth muscles in blood vessels , and the d2 receptor , which inhibits noradrenaline release from postganglionic sympathetic neurons .
these two effects could explain the pre - operative hypotension in dopamine secreting tumor patients .
blood pressure is sometimes elevated after the removal of this tumor presumably because of the same mechanism .
dopamine secreting paragangliomas are more likely to present malignant features than classic catecholamine secreting type paragangliomas or pheochromocytomas .
this rare tumor tends to be diagnosed in patients who are asymptomatic , and the tumor is detected later than tumors that secrete norepinepnrine , epinephrine or both .
concerning the biochemical features , one report suggests that the decreased activity of dopamine -hydroxylase results in poor differentiation of this tumor , which may explain why the dopamine - secreting type shows advanced malignant features .
elevated dopamine or hva levels in 24-hour urine ( > 120 nmol / g ) is correlated with large tumor size and malignant potential .
extra - adrenal location , a tumor weight of more than 80 g , dna aneuploidy or triploidy and persistent postoperative hypertension have also been reported as risk factors for malignant pheochromocytoma . because of the rarity of this tumor , there are no definite criteria for evaluating its malignant potential . in conclusion ,
lack of clinical symptoms and the rarity of this tumor can lead to the lack of , or a delay in diagnosis .
in addition to radiologic imaging , dopamine assays in serum and 24-hour urine collection are useful diagnostic tests .
 exclusively dopamine producing retroperitoneal paragangliomas are extremely rare . 
 we have experienced the first korean case managed successfully based on the proper evaluation . 
 a 26-year - old female patient came to our attention after the accidental detection of an adrenal mass . 
 she had no symptoms and denied any family history . 
 laboratory evaluations were normal but serum dopamine ( 425 
 ng / l ) and 24-hour urine dopamine levels ( 1,565.3 g / day ) were elevated . 
 she underwent laparoscopic right adrenalectomy . 
 histopathological diagnosis was a paraganglioma . 
 after operation , dopamine levels in serum and 24-hour urine dropped to 0.09 ng / l and 388.4 g / day . 
 dopamine producing paraganglioma elicit no clinical symptoms . 
 only the dopamine level is elevated in serum and 24-hour urine samples . 
 surgical resection without using preoperative alpha blockage is the treatment of choice . 
 the prognosis for patients with this tumor tends to be poor because the diagnosis is usually delayed due to lack of symptoms . 
INTRODUCTION
CASE REPORT
DISCUSSION