Pheochromocytoma is a catecholamine secreting tumor originating from the adrenal 
medulla (up to 90%), or from the chromaffin tissue along the paravertebral 
sympathetic chain. The hallmark of pheochromocytoma is paroxysmal hypertension 
associated with diaphoresis, headache, tremulousness, and palpitations. The 
triad of diaphoresis, tachycardia, and headache in hypertensive patients is 
highly suggestive of pheochromocytoma. Other symptoms like flushing, nausea, 
vomiting, personality changes, and visual disturbances may however cast doubt on 
the diagnosis of pheochromocytoma. Death resulting from pheochromocytoma is 
usually due to congestive heart failure, myocardial infarction, or intracerebral 
hemorrhage. Although less than 0.1 percent of patients with hypertension have a 
pheochromocytoma, nearly 50 percent of the mortality with unsuspected 
pheochromocytoma occurred during anesthesia and surgery or parturition. Patients 
of unsuspected pheochromocytoma have higher risk for surgery, because some 
mandatory pre-op medical treatments might have been ignored. It is also a 
challenge to anesthesiologists to handle unsuspected hypertensive crisis during 
anesthesia and surgery. We presented such a case of unexpected Pheochromocytoma 
which was mis-diagnosed by the surgeon and was treated as an ordinary adrenal 
gland tumor and was scheduled for surgical operation. When the patient was 
undergoing excision of the tumor, manipulations of the tumor initiated an 
tremendous elevation of the blood pressure. Upon reviewing her history of 
normotension with visual disturbance, nausea and restlessness, she was immediate 
treated as with a pheochromocytoma. Appropriate managements were applied to 
control her abnormally high fluctuating blood pressure with success and with no 
complications or adverse effect.(ABSTRACT TRUNCATED AT 250 WORDS)