[Clinical characteristics of silent pheochromocytoma]

Objective: To summarize the clinical characteristics of silent paraganglioma. Methods: A total of 247 pheochromocytoma cases in Peking University First Hospital between January 1993 and December 2015 were analyzed retrospectively.The cases were divided into two groups according to whether they had hypertension: non-silent group (193 cases) and silent group (53 cases), then the clinical characteristics between the groups were compared, and the clinical features of silent pheochromocytoma were reviewed. Results: There were 53 silent pheochromocytoma cases in this study, which accounted for 21.5% (53/247), and imaging was the main way to find the tumor. Forty-one in 53 cases (77.4%) located in adrenal gland, in which 31 cases (75.6%) were benign and 2.3-8.0 cm in diameter, while 10 cases (24.4%) were malignant and 3.5-12.0 cm in diameter. Twelve in 53 cases (22.6%) located in extra-adrenal tissue, in which 4 cases were benign and 2.0-5.5 cm in diameter, while 8 cases were malignant and 5.0-10.5 cm in diameter. With the tumor diameter increased, the malignant rate increased: 1 in 8 cases in diameter<3 cm, 2 in 12 cases in diameter 3-5 cm, 15 in 33 cases in diameter>5 cm were malignant. There was no significant difference in age, sex, tumor location, benign or malignant rate between the two groups (all P>0.05). Compared with the non-silent group, the proportion of tumor size≥5 cm in silent group was significantly higher (62.3% vs 45.9%, P=0.034), and the incidence of hyperglycemia and the concentrations of norepinephrine and epinephrine were lower (all P<0.05) in silent group.Misdiagnosis was common in silent group, and up to 35.8% (19/53) had not been diagnosed correctly before operation. Twenty-one in 53 (39.6%) silent pheochromocytoma cases occured severe intra-operative blood pressure fluctuation. Conclusions: Silent pheochromocytoma was not uncommon and imaging was the main way to find it. The tumor size was always big and misdiagnosis was common, especially extra-adrenal tumors. Therefore, regardless of the adrenal or extra-adrenal tumors, especially in diameter>3.0 cm but with normal blood pressure, the possibility of silent pheochromocytoma should be considered. In order to reduce misdiagnosis and intra-operative blood pressure fluctuations, preoperative diagnosis and preparation, as well as intra-operative monitoring should be fully made.