Radiology Page
Incidental Adrenal Pheochromocytoma A 77-year-old black female presenting with back pain was evaluated with noncontrast enhanced computerized tomography (CT) for renal stones. A 4 cm right adrenal mass was incidentally detected, which was well circumscribed with soft tissue density (30 HU) (fig. 1). An adrenal mass is considered “incidental” when discovered during an imaging study performed for an indication other than evaluation of adrenal disease. Most often the imaging study is CT but occasionally it is magnetic resonance imaging (MRI) or ultrasound. Incidental adrenal lesions are fairly common, occurring in 3% to 7% of adults, and the majority are benign.1 The differential diagnosis of an incidentally detected adrenal mass includes metastatic disease and primary adrenal lesions such as adenoma, adrenocortical carcinoma, pheochromocytoma, hemorrhage, cyst and myelolipoma. Metastatic disease to the adrenal gland in a patient without a known primary tumor is unusual.2 Evaluation of an incidental adrenal lesion usually
Figure 1. Unenhanced axial CT shows homogeneous 4 cm right adrenal mass with CT density of 30 HU (arrow) posterior to inferior vena cava.
0022-5347/14/1921-0238/0 THE JOURNAL OF UROLOGY® © 2014 by AMERICAN UROLOGICAL ASSOCIATION EDUCATION
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begins with a careful history and physical examination with specific focus on evidence of hormonal dysfunction and malignancy. Laboratory evaluation will include an overnight dexamethasone suppression test, measurement of urinary fractionated metanephrines and catecholamines, and if there is a history of hypertension, measurement of plasma aldosterone and plasma renin activity. The American College of Radiology Incidental Findings Committee offers an algorithm for evaluation for an incidentally detected adrenal mass.1 Presence of macroscopic fat on CT or MRI is diagnostic of an adrenal myelolipoma. For a lesion smaller than 4 cm, a CT density less than 10 HU on an unenhanced CT study is diagnostic of a lipid-rich adrenal adenoma. On MRI signal decrease between in-phase and opposed-phase T1-weighted imaging is also diagnostic of a lipid-rich adrenal adenoma. If these features are absent, management is dependent upon lesion size and medical history. For a lesion larger than 4 cm, resection is recommended if there is no history of cancer due to a slight possibility of adrenal cortical carcinoma. If there is a history of cancer, positron emission tomography CT or biopsy is recommended to assess for the possibility of metastatic disease to the adrenal gland. If the lesion is between 1 and 4 cm, and has been stable for more than a year, it is considered benign. If the lesion demonstrates growth, biopsy or resection is appropriate. If there are no prior images for comparison and the lesion has benign features such as homogenous low density and smooth margins, it may be followed with CT or MRI in 12 months. If the lesion demonstrates more suspicious imaging findings, such as heterogeneous enhancement with necrosis or irregular margins, adrenal protocol CT or MRI can help clarify whether the adrenal mass is a lipid-poor adenoma or a nonadenoma. Adrenal protocol CT includes noncontrast, early (70 seconds) and delayed (15 minutes) post-contrast images. Absolute [(early post-contrastdelayed postcontrast HU) O (early post-contrast HUnoncontrast HU)] and relative (if there is no unenhanced phase)
http://dx.doi.org/10.1016/j.juro.2014.04.022 Vol. 192, 238-239, July 2014 Printed in U.S.A.
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Figure 2. Adrenal CT washout protocol. Coned-in axial CT images show right adrenal mass (arrow) between inferior vena cava (short arrow) and liver. Homogeneous soft tissue density (30 HU) on noncontrast CT (A), heterogeneous but hypervascular enhancement (154 HU) on standard post-contrast CT (B) and homogeneous density (90 HU) on 15-minute delayed post-contrast CT (C ). Calculated absolute washout value is 52%, less than the 60% used for adrenal adenoma. Regardless, washout values are not necessarily diagnostic in setting of elevated catecholamines.
washout values [(early post-contrastdelayed postcontrast HU) O early post-contrast HU] are calculated. If the absolute washout is greater than 60% or the relative washout is greater than 40%, the lesion can definitively be called an adenoma. Biopsy is needed if there is concern for the exact diagnosis of a nonadenoma. In this patient the incidentally discovered adrenal mass did not meet criteria for a definitive imaging diagnosis since there was neither macroscopic fat nor HU less than 10 on nonenhanced imaging. Therefore a contrast enhanced dedicated adrenal protocol CT was obtained pending laboratory values, which showed marked heterogeneous early enhancement with an absolute washout of 52% (fig. 2). Therefore, the lesion was considered indeterminate based on imaging criteria. On clinical evaluation the patient had mild hypertension and urinary metanephrines were mildly elevated suggestive of a pheochromocytoma. Approximately 5% of incidental adrenal lesions prove to be pheochromocytoma.3 Pheochromocytomas can have variable imaging characteristics and are considered to be chameleons of other adrenal lesions. On imaging a pheochromocytoma may appear as a heterogeneous mass with hemorrhagic or cystic components and may contain calcifications.
The mean size is 4 cm.4 When solid it demonstrates marked heterogeneous contrast enhancement as in this case, and will have inconsistent washout patterns. Therefore, there is no benefit to imaging clinically suspected pheochromocytoma with a dedicated adrenal protocol, and imaging may be done for localization (as approximately 10% are bilateral) and surgical planning. Our patient underwent retroperitoneal laparoscopic adrenalectomy and pathological diagnosis was pheochromocytoma. Tracie Rehfuss and Namita Gandhi Imaging Institute Cleveland Clinic Cleveland, Ohio 1. Berland L, Silverman S, Gore R et al: Managing incidental findings on abdominal CT: white paper of the ACR Incidental Findings Commmittee. J Am Coll Radiol 2010; 7: 754. 2. Song JH, Chaudhry FS and Mayo-Smith WW: The incidental adrenal mass on CT: prevalence of adrenal disease in 1,049 consecutive adrenal masses in patients with no known malignancy. AJR Am J Roentgenol 2008; 190: 1163. 3. Young W: The incidentally discovered adrenal mass. N Engl J Med 2007; 356: 601. 4. Raja A, Leung K, Stamm M et al: Multi-modality imaging findings of pheochromocytoma with associated clinical and biochemical features in 53 patients with histologically confirmed tumors. AJR Am J Roentgenol 2013; 201: 825.
Incidental Adrenal Pheochromocytoma A 77-year-old black female presenting with back pain was evaluated with noncontrast enhanced computerized tomography (CT) for renal stones. A 4 cm right adrenal mass was incidentally detected, which was well circumscribed with soft tissue density (30 HU) (fig. 1). An adrenal mass is considered “incidental” when discovered during an imaging study performed for an indication other than evaluation of adrenal disease. Most often the imaging study is CT but occasionally it is magnetic resonance imaging (MRI) or ultrasound. Incidental adrenal lesions are fairly common, occurring in 3% to 7% of adults, and the majority are benign.1 The differential diagnosis of an incidentally detected adrenal mass includes metastatic disease and primary adrenal lesions such as adenoma, adrenocortical carcinoma, pheochromocytoma, hemorrhage, cyst and myelolipoma. Metastatic disease to the adrenal gland in a patient without a known primary tumor is unusual.2 Evaluation of an incidental adrenal lesion usually
Figure 1. Unenhanced axial CT shows homogeneous 4 cm right adrenal mass with CT density of 30 HU (arrow) posterior to inferior vena cava.
0022-5347/14/1921-0238/0 THE JOURNAL OF UROLOGY® © 2014 by AMERICAN UROLOGICAL ASSOCIATION EDUCATION
238
j
www.jurology.com
AND
RESEARCH, INC.
begins with a careful history and physical examination with specific focus on evidence of hormonal dysfunction and malignancy. Laboratory evaluation will include an overnight dexamethasone suppression test, measurement of urinary fractionated metanephrines and catecholamines, and if there is a history of hypertension, measurement of plasma aldosterone and plasma renin activity. The American College of Radiology Incidental Findings Committee offers an algorithm for evaluation for an incidentally detected adrenal mass.1 Presence of macroscopic fat on CT or MRI is diagnostic of an adrenal myelolipoma. For a lesion smaller than 4 cm, a CT density less than 10 HU on an unenhanced CT study is diagnostic of a lipid-rich adrenal adenoma. On MRI signal decrease between in-phase and opposed-phase T1-weighted imaging is also diagnostic of a lipid-rich adrenal adenoma. If these features are absent, management is dependent upon lesion size and medical history. For a lesion larger than 4 cm, resection is recommended if there is no history of cancer due to a slight possibility of adrenal cortical carcinoma. If there is a history of cancer, positron emission tomography CT or biopsy is recommended to assess for the possibility of metastatic disease to the adrenal gland. If the lesion is between 1 and 4 cm, and has been stable for more than a year, it is considered benign. If the lesion demonstrates growth, biopsy or resection is appropriate. If there are no prior images for comparison and the lesion has benign features such as homogenous low density and smooth margins, it may be followed with CT or MRI in 12 months. If the lesion demonstrates more suspicious imaging findings, such as heterogeneous enhancement with necrosis or irregular margins, adrenal protocol CT or MRI can help clarify whether the adrenal mass is a lipid-poor adenoma or a nonadenoma. Adrenal protocol CT includes noncontrast, early (70 seconds) and delayed (15 minutes) post-contrast images. Absolute [(early post-contrastdelayed postcontrast HU) O (early post-contrast HUnoncontrast HU)] and relative (if there is no unenhanced phase)
http://dx.doi.org/10.1016/j.juro.2014.04.022 Vol. 192, 238-239, July 2014 Printed in U.S.A.
RADIOLOGY PAGE
239
Figure 2. Adrenal CT washout protocol. Coned-in axial CT images show right adrenal mass (arrow) between inferior vena cava (short arrow) and liver. Homogeneous soft tissue density (30 HU) on noncontrast CT (A), heterogeneous but hypervascular enhancement (154 HU) on standard post-contrast CT (B) and homogeneous density (90 HU) on 15-minute delayed post-contrast CT (C ). Calculated absolute washout value is 52%, less than the 60% used for adrenal adenoma. Regardless, washout values are not necessarily diagnostic in setting of elevated catecholamines.
washout values [(early post-contrastdelayed postcontrast HU) O early post-contrast HU] are calculated. If the absolute washout is greater than 60% or the relative washout is greater than 40%, the lesion can definitively be called an adenoma. Biopsy is needed if there is concern for the exact diagnosis of a nonadenoma. In this patient the incidentally discovered adrenal mass did not meet criteria for a definitive imaging diagnosis since there was neither macroscopic fat nor HU less than 10 on nonenhanced imaging. Therefore a contrast enhanced dedicated adrenal protocol CT was obtained pending laboratory values, which showed marked heterogeneous early enhancement with an absolute washout of 52% (fig. 2). Therefore, the lesion was considered indeterminate based on imaging criteria. On clinical evaluation the patient had mild hypertension and urinary metanephrines were mildly elevated suggestive of a pheochromocytoma. Approximately 5% of incidental adrenal lesions prove to be pheochromocytoma.3 Pheochromocytomas can have variable imaging characteristics and are considered to be chameleons of other adrenal lesions. On imaging a pheochromocytoma may appear as a heterogeneous mass with hemorrhagic or cystic components and may contain calcifications.
The mean size is 4 cm.4 When solid it demonstrates marked heterogeneous contrast enhancement as in this case, and will have inconsistent washout patterns. Therefore, there is no benefit to imaging clinically suspected pheochromocytoma with a dedicated adrenal protocol, and imaging may be done for localization (as approximately 10% are bilateral) and surgical planning. Our patient underwent retroperitoneal laparoscopic adrenalectomy and pathological diagnosis was pheochromocytoma. Tracie Rehfuss and Namita Gandhi Imaging Institute Cleveland Clinic Cleveland, Ohio 1. Berland L, Silverman S, Gore R et al: Managing incidental findings on abdominal CT: white paper of the ACR Incidental Findings Commmittee. J Am Coll Radiol 2010; 7: 754. 2. Song JH, Chaudhry FS and Mayo-Smith WW: The incidental adrenal mass on CT: prevalence of adrenal disease in 1,049 consecutive adrenal masses in patients with no known malignancy. AJR Am J Roentgenol 2008; 190: 1163. 3. Young W: The incidentally discovered adrenal mass. N Engl J Med 2007; 356: 601. 4. Raja A, Leung K, Stamm M et al: Multi-modality imaging findings of pheochromocytoma with associated clinical and biochemical features in 53 patients with histologically confirmed tumors. AJR Am J Roentgenol 2013; 201: 825.
