Case report: A Re-operation Case of Asymptomatic Left Giant Pheochromocytoma and Literature Review

Introduction : Pheochromocytoma (PCC) is a rare tumor which derives from adrenal medulla, when maximum diameter of pheochromocytoma is greater than 10CM, it is divided into Giant pheochromocytoma(GPCC), which is extremely rare and usually asymptomatic.Clinically, a huge and asymptomatic adrenal pheochromocytoma was usually misdiagnosed as other types of tumors, which result in notable increase of complication rates and death rates. Case presentation :In this case report, we described a clinically asymptomatic GPCC patient. Diagnosis :According to computed tomography (CT) scan, nuclear magnetic resonance(MR) scan, the patient is initially diagnosed as liposarcoma.After laparotomy, biochemical detection of catecholamine (CA) intermediate metabolites methoxyepinephrine (MN) and methoxy norepinephrine (NMN) and the pathological examination , diagnosis of GPCC was obtained. Intervention The laparotomy was suspended and a diagnosis of pheochromocytoma was confirmed, because of unstable blood pressure and hypertension during separating and moving the mass during surgery. After consultation of multi-disciplinary team, adequate preoperative preparation was conducted according to the procedure of PCC surgical preparation. By the end of the regular phenoxybenzamine and intravenous fluids treatment for three weeks, the blood pressure of the patient was kept at an acceptable average. Therefore, the patient underwent the operationagain for radical resection. Outcome : After the operation, CA was basically normal in rechecking process, and the tumor was successfully removed. Pathological diagnosis of the mass after operation: Immunohistochemical resulted conformed to (epigastrium) pheochromocytoma. Immunohistochemistry: CgA(+), Inhibin-α(-), ki-67(<1%+), Syn(+). Pheochromocytoma had the definite pathological diagnosis. Conclusion : GPCC has the high diagnostic identification difficulty, it should be combined with imaging examination and biochemical measurement to identify. Before operation, the detailed imageological examination provides important reference for excision and surgical planning. Individualized and multi-disciplinary cooperation of management strategy in perioperative period

4 Pheochromocytoma (PCC) is a rare tumor which derives from adrenal medulla, leading to aseries of clinical syndromes through synthesis or release of catecholamine (CA), with main manifestations of hypertension and its complications. [1] Clinically, most adrenal tumors larger than 7 cm are often found to be dysfunctional malignancies.. PCC could secrete catecholamines continuously or intermittently with different proportion. Adrenergicreceptor is widely distributed in a variety of body tissues and cells, leading to clinical manifestations and individual variations. A small proportion of patients can be asymptomatic. Clinically, a huge and asymptomatic adrenal pheochromocytoma was usually misdiagnosed as other types of tumors, which result in notableincrease of complication rates and death rates. Although surgery remains the primary therapy option for patients with large adrenal tumor, it is still a huge challenge for abdominal surgeons because of difficult exposure, high morbidity rates of cardiovascular complication, metastasis and invasion of huge tumors. In this case report, we described a clinically asymptomatic GPCC patient who had surgery to remove a 18cm×21cmⅹ19cmhuge tumor mass in November 2017, with a good postoperative recovery and no complications. Now it is reported as follows.

Disease history and auxiliary examination
The patient was a 30-year-old man with an abdominal mass more than 4 months examined by abdominal B-ultrasound in outpatient pharmacy of our hospital and suggested an occupying lesion in abdomen. Then retroperitoneal tumors was diagnosed and admitted in the hospital. The patient had no abdominal distension, abdominal pain, constipation, diarrhea, dizziness, headache, palpitation, shortness of breath, back pain, or progressive emaciation, his previous medical history is without any paroxysm hypertension, diabetes, surgery or trauma. The patient's mother and father are healthy. No family history of diseases or tumors. Physical examinations: Temperature 37.2℃, Heart rate 63 times/min, Respiration18 times/min Blood pressure 120/80mmHg. A crucial finding on physical examination is obvious protrusion mass in upper left abdomen approximately 15cm×12cm in size.
The abdomen is supple without epigastric varicose veins or tenderness, rebound tenderness. Some additional tests were performed after admission, such as "three great regular tests", second liver two half-and-half detect, three indexes before blood transfusion, four coagulation tests, 36 biochemical indexes, tumor markers , Chest radiographs, and showed no abnormalities. After consultation of multi-disciplinary team, adequate preoperative preparation was conducted according to the procedure of PCC surgical preparation. By the end of the regular phenoxybenzamine and intravenous fluids treatment for three weeks, the blood pressure of the patient was kept at an acceptable average (100-120mmHg/60-80mmHg), heart rate60-90 beats /min . Erratic blood pressure only appeared before sleep (Systolic pressure100-150mmHg). Therefore, the patient underwent the operation again on November 15, 2017. After the operation, the patient was sent to ICU for nursing. In the second day after operation, the patient had a fever. After the patient accepted anti-infective therapy, vital signs gradually tended to be smooth. After the third week of operation, CA was basically normal in rechecking process.
Considering that the tumor was cut off successfully, the patient was allowed to discharge from the hospital. Pathological diagnosis of the mass after operation: 1. Immunohistochemical resulted

Discussion
Pheochromocytoma is a rare tumor that is originated from adrenal medulla. It is estimated that the morbidity of global people is 0.005-0.1%. [2] The clinical symptoms of the typical pheochromocytoma are reflected in paroxysmal headache, perspiration and palpitation. Continuous hypertension is generally considered as one of important clinical performances, while in all pheochromocytoma cases, only a few patients will have normal blood pressure or have no symptoms. The morbidity of the asymptomatic pheochromocytoma is estimated as 21% of PCC total morbidity. [1] When maximum diameter of pheochromocytoma is greater than 10CM, it can be divided into Giant pheochromocytoma(GPCC), which is extremely rare and asymptomatic. [3] By existing English literatures, We speculate the reason why such pheochromocytoma patients have no symptoms is that the giant tumor center has the bigger necrosis area for insufficient nutrition and blood supply, thus the cell number of catecholamine is reduced. At the same time, more tumor stroma and desmoplasia will form the saccular structure. Catecholamine and metabolite generated by tumors will be stored in it. As conducting the resection operation, due to touch extrusion and tumor separation, such a saccular structure is destroyed. Lots of catecholamine will be released in blood, resulting in hypertensive crisis. [4][5][6] In in plasma and the small plasma concentration fluctuation. Therefore, the specificity and the sensibility are better than catecholamine measurementas diagnosing pheochromocytoma, but the positive rate is only 20%,blood or urine NE, E and dopamine(DA) measurement can be used for auxiliary diagnosis. In addition, the terminal metabolite vanillyl mandelic acid (VM-A) can be used for measurement to diagnosis, but the specificity is 86%-99%, blood and urine CA levels should be measured simultaneously for definitive diagnosis. [8] Imaging examination is used for localization diagnosis ( Table 1). The sensibility of abdominal CT scan or magnetic resonance imaging (MRI) for pheochromocytoma is 90-100%. Specificity is 70-80%. [2] Besides, 131 I-MIBG is a very sensitive tool to detect pheochromocytoma, but as using this method by alone, its sensitivity is only 83.7%. If it is combined with the plasma noradrenaline, sensitivity is up to 97.1%. Noradrenaline from urine/MIBG is 96.6%. Noradrenaline in urine/MIBG is 95.3%. Blood platelet noradrenaline/MIGB is even up to 100%. [9] As a result, if there is suspected diagnosis of pheochromocytoma in clinics and catecholamine is kept in the normal range, we advocate conducting MIBG scanning.
For GPCC, once it makes a definite diagnosis and positioning, the first treatment should be operative excision. Early, suitable and appropriate acceptance of adrenergic receptor before operation can avoid from serious complications. Even if there is no official guide about blocking drug types, the currently used drugs mainly include α adrenergic retardant and calcium antagonist. The main objectives aim to normalize hemodynamics, including blood pressure, heart rate and liquid condition in blood vessels. Preoperative average treatment time is 2-6 weeks. α-receptor retardant including phenoxybenzamine and doxazosin is recommended as the front-line drugs. Calcium antagonist including nifedipine and amlodipine acts as the replaced drug or drug combination. Furthermore, βreceptor retardant is used to control tachycardia. In this case, phenoxybenzamine was used. [10] Considering specificity of GPCC, we conducted MDT consultation before the second operation.
According to the patient's situation, α-receptor retardant use scheme, fluid infusion scheme and operation mode were formulated individually, laying a foundation on success of operation. For the selection of the operation mode, multiple guides recommend to use excision of laparoscopic surgery. hypertensive crisis in operation to capacity. [11] Lots of pheochromocytoma is a benign tumor, while the patients with malignant tumor account for 10%. With the increase of tumor size, the malignant probability is also increasing. Five-year survival rate of benign tumors is 95%, while that of malignant tumors is 5%. At present, GPCC has no specific detection to accurately remind malignant lesions, thus postoperative follow-up is also important. The patient should recheck for once-twice every year. [12] If it is malignant, 131 I-MIBG treatment should be considered. [13] 4.