Radiological Features of Pheochromocytoma Compared to Non-Pheochromocytoma

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 37-82-Pheochromocytoma & Paraganglioma
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-53
Subramanian Kannan*1, Andrei Purysko2, Mamatha Chella2, Erick Remer2, Eren Berber3, Charles Faiman1 and Amir Hekmat Hamrahian1
1Cleveland Clinic Foundation, Cleveland, OH, 2Cleveland Clinic Foundation, 3Cleveland Clinic, Cleveland, OH
Introduction: Pheochromocytoma (PHEO) comprises about 3% of patients with adrenal incidentaloma (AI).  Plasma or urinary metanephrines are commonly used to rule out PHEO in patients with AI. It is desirable to avoid unnecessary biochemical evaluation, which may be associated with a false positive result. Recent data suggests that ruling out PHEO in patients with homogenous lipid rich (<10 Hounsfield units, HU) adrenal masses is not needed (1).

Objective: To identify additional radiological features that can help to differentiate adrenal PHEOs from non-PHEOs

Methods: We retrospectively studied 112 patients with pathologically proven adrenal PHEO and 125 patients with lipid poor, non-PHEO adrenal masses from 1997-2012.

Results: The median (range) pre-contrast (Pr-C) attenuation for PHEOs (n=66) was 35 HU (17 - 59) compared to 27 HU (10 - 57) in lipid poor non-PHEOs (n=125) (P<0.001). Post-contrast (Po-C) images performed at the porto-venous phase were available in 18 PHEOs and 34 lipid poor non-PHEOs as part of adrenal CT protocol. The median (range) of Po-C attenuation among PHEOs and non-PHEOs was 88 HU (31 - 137) and 34 HU (17 - 134) respectively (P = 0.037). Median difference between Po-C HU and Pr-C HU (Delta) in PHEOs was 53 HU (14-105) compared to 43 HU (0-95) in non-PHEOs (P =0.315). While hemorrhage was more common among lipid poor non-PHEOs (18% vs 5%; P = 0.027), necrosis and hypervascularity were more common among the PHEOs (61% vs 19%; P <0.001) and (57% vs 28%; P = 0.001) respectively. 

Discussion: All PHEOs in our series had a Pr-C attenuation >16 HU. A Po-C HU> 30 had 100% sensitivity and 26% specificity for diagnosis of PHEO.

Conclusion: Our data further confirms that PHEO work up for AI with a Pr-C attenuation value <10 HU is not needed. There is considerable overlap in Po-C attenuation values between PHEOs and non-PHEOs. A Po-C >30HU had limited specificity in excluding PHEO. Radiological features of necrosis and hypervascularity, when present, favors a diagnosis of PHEO.

1. Sane T, Schalin-Jantti C, Raade M. Is biochemical screening for pheochromocytoma in adrenal incidentalomas expressing low unenhanced attenuation on computed tomography necessary? J Clin Endocrinol Metab. 2012 Jun;97(6):2077-83.

Disclosure: CF: Speaker Bureau Member, Vivus USA. AHH: Consultant, Corcept. Nothing to Disclose: SK, AP, MC, ER, EB

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