Atypical Imaging Features of Pheochromocytoma

Presentation Number: SAT 392
Date of Presentation: April 1st, 2017

Sanjeda Sultana*, Sonia K Hans and Steven N Levine
Louisiana State University Health Sciences Center, Shreveport, LA

Abstract

Background:

CT imaging of pheochromocytomas almost always reveals precontrast attenuation of greater than 10 HU, are heterogeneous on venous phase imaging, and <50% washout on delayed phase. In fact, some authorities suggest that biochemical evaluation for pheochromocytomas is unnecessary when precontrast HU are <10.2 We report a patient with a pheochromocytoma with precontrast HU of 2.

Clinical Case:

A 36 year old female was referred for an incidentally discovered left adrenal mass during a workup for groin pain and an enlarged lymph node. She reported an increasing frequency of paroxysmal episodes consisting of diaphoresis, palpitations, flushing and increased systolic hypertension (up to 160 mm Hg) that lasted for 1 hour and spontaneously resolved. These episodes started 2-3 years ago and increased in frequency to 2-3 times per week over the past year. On exam her BP was 140/90 mm Hg with no orthostasis. Her past medical history included anxiety and hypertension, diagnosed at 21 years of age treated with lisinopril.

24 hour urine normetanephrines were 3412 ug/24h (82-500), metanephrines 160 ug/24h (45-290), norepinephrine 447 ug/24h (0-135). On CT imaging at our facility the left adrenal mass measured 4.8 cm x 1.8 cm x 4.2 cm with homogeneous non-contrast attenuation of 2HU, heterogeneous attenuation of 80HU in portal venous phase while 15 minute delayed attenuation of 20HU. Absolute washout was 76%.

History, and biochemical assessment confirmed a pheochromocytoma despite imaging of the left adrenal mass with HU <10. She was optimized on alpha- and beta-adrenergic blockade prior to left adrenalectomy. Pathology showed an 8 cm x 2.5 cm x 2 cm pheochromocytoma extending into the periadrenal adipose tissue with invasion into the capsule. In the immediate postoperative period the patient did not require anti-hypertensive medications.

Conclusion:

Clinical suspicion and laboratory assessment indicated our patient had a pheochromocytoma, while the diagnosis of a pheochromocytoma was less likely based on non-contrast attenuation data published in the peer reviewed medical literature. This is a reminder that while 87-100% of pheochromocytomas exhibit precontrast attenuation HU of >101, rare cases present with HU<10.

 

Nothing to Disclose: SS, SKH, SNL