The “Prebiochemical” Pheochromocytoma

All pheochromocytomas are biochemically undetectable when small—they require a sizable “factory” to become biochemically detectable. Thus publications that report that a laboratory test is 98% or 100% sensitive in detecting pheochromocytomas is simply wrong—just not possible! Computed abdominal imaging is being performed for a never-ending list of reasons. We are finding “baby” pheochromocytomas before they become symptomatic or biochemically detectable. Herein is such a case.

Case Report

The patient was a healthy 49-year-old man who had been troubled by intermittent right upper quadrant pain, which was thought to be related to gallbladder dysfunction. Abdominal computed tomography (CT) incidentally discovered a 1.6-cm lipid-poor and vascular left adrenal mass ( Fig. 36.1 ). He had no signs or symptoms of adrenal cortical or medullary dysfunction. He took no regular medications. His blood pressure was 128/78 mmHg, heart rate 74 beats per minute, and body mass index 26.51 kg/m ² .

INVESTIGATIONS

All adrenal-related laboratory studies normal ( Table 36.1 ).

TABLE 36.1

Laboratory Tests

Biochemical Test	Result	Reference Range
Sodium, mmol/L	142	135–145
Potassium, mmol/L	4.2	3.6–5.2
Creatinine, mg/dL	1.15	0.74–1.35
am serum cortisol, mcg/dL	16	7–25
ACTH, pg/mL	44	10–60
Plasma metanephrine, nmol/L	<0.2	<0.5
Plasma normetanephrine, nmol/L	0.55	<0.9
Aldosterone, ng/dL	5.3	≤21 ng/dL
Plasma renin activity ng/mL per hour	2	≤0.6–3
24-Hour urine:
Metanephrine, mcg	151	<400
Normetanephrine, mcg	447	<900
Norepinephrine, mcg	61	<80
Epinephrine, mcg	7.6	<20
Dopamine, mcg	201	<400