Case 11
History:
45 year old male on whom a recent CT scan for chronic abdominal pain showed a left adrenal mass. The patient has a medical history of Type II diabetes, hypercholesterolemia and hypertension.
Findings:
An abdominal CT showed a MRI of the abdomen demonstrating a 4 cm enhancing left adrenal mass lesion. The corresponding MRI showed a fairly well-circumscribed left adrenal mass of intermediate signal intensity on axial T1- WI and increased T2-WI signal associated heterogenous enhancement is identified on post Gadolinium images. An MIBG scan showed tracer accumulation within the lesion.
Diagnosis:
Pheochromocytoma (Pathologically proven)
Discussion:
Pheochromocytomas are most common in the fourth through sixth decades of life. They have been called the “Ten Percent” as about 10% are bilateral, 10% are malignant, 10% occur in children, and 10% are extraadrenal. They arise from the adrenal medulla and the sympathetic paraganglia. They can be associated with Multiple Endocrine Neoplasia, Von Hippel-Lindau Disease, NF1. Elevated levels of urinary metanephrine or resting plasma catecholamines can suggest the diagnosis of pheochromocytoma (97% sensitivity for the urinary catecholamines and 99% for plasma catecholamines).
On MRI, pheochromocytomas have been described as enhancing masses having characteristic high signal intensity on T2-weighted imaging, best appreciated with the use of fat suppression. They are typically heterogeneous. Although the classic T2 appearance has been previously described as a light bulb bright signal on T2-weighted imaging, this is neither specific nor sensitive, and the use of this sign leads to the misdiagnosis of pheochromocytoma in up to 35% of cases.
References:
- Disler DG, et al: Adrenal Pheochromocytoma. AJR; 158:1056, 1992.
- MRI of Adrenal and Extraadrenal Pheochromocytom. Khaled M. Elsayes1, Vamsidhar R. Narra1, John R. Leyendecker2, Isaac R. Francis3, James S. Lewis, Jr.4 and Jeffrey J. Brown . AJR 2005; 184:860-867.
