Biochemical and radiological relationships in patients with pheochromocytoma: lessons from a case control study.
BACKGROUND
An elevation of fractionated plasma or urinary metanephrine (MN) or nor-metanephrine (NMN), collectively called metanephrines (MN and NMN), >4-fold above the upper limit of normal (ULN) is usually considered to be diagnostic for pheochromocytoma (PHEO). There are a greater number of false positive results when the elevations are more modest.


OBJECTIVE
To identify biochemical and radiological features in PHEOs with modest elevations (<4-fold above ULN) of metanephrines.


METHODS
We retrospectively reviewed the charts of 112 patients with PHEO (10% extra-adrenal) and 208 patients with a non-PHEO adrenal mass operated from 1997-2011, who had metanephrines measured pre-operatively. We divided PHEO into group 1 (n = 90) with metanephrines ≥4-fold ULN and group 2 (n = 22) with metanephrines <4-fold ULN. The non-PHEO group was designated as group 3.


RESULTS
The median (range) tumour size in group 1 and group 2 was 4·8 cm (1·7-22) and 3·0 cm (1·7-5) respectively (P < 0·001). All patients with PHEO in group 2 had a tumour <5 cm in size. The MN fraction was elevated in about 65% of groups 1 and 2; only 2 (1%) patients in group 3 had an elevated urinary MN fraction, and none were associated with an elevated plasma MN fraction. All PHEOs had a pre-contrast attenuation ≥17 Hounsfield Units (HU).


CONCLUSIONS
Modest elevations (<4-fold ULN) of the NMN fraction in an adrenal mass >5 cm are almost always falsely positive. Elevations in plasma and urinary MN fraction are less likely to be false positive. The CT pre-contrast attenuation of PHEOs is >10 HU.
Department of Endocrinology and Metabolism, Cleveland Clinic Foundation, Cleveland, OH, USA.
Subramanian
S
Kannan
Andrei
A
Purysko
Charles
C
Faiman
Erick M
EM
Remer
Lisa
L
Shah
James
J
Bena
Allan
A
Siperstein
Eren
E
Berber
Amr
A
Fergany
Emmanuel
E
Bravo
Amir H
AH
Hamrahian
D000293:Adolescent; D000310:Adrenal Gland Neoplasms / Q000097:blood* / Q000000981:diagnostic imaging / Q000652:urine*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D002648:Child; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008297:Male; D008676:Metanephrine / Q000097:blood* / Q000652:urine; D008875:Middle Aged; D061330:Multidetector Computed Tomography; D009647:Normetanephrine / Q000097:blood / Q000652:urine; D010673:Pheochromocytoma / Q000097:blood* / Q000000981:diagnostic imaging / Q000652:urine*; D012189:Retrospective Studies; D055815:Young Adult
D009647:Normetanephrine; D008676:Metanephrine