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Letters to the Editor |
,
Giles W. Boland, MD and
Peter F. Hahn, MD, PhD
* Department of Radiology, Emory University Hospital, Atlanta, Ga
Department of Radiology, Division of Abdominal Imaging and Intervention, Massachusetts General Hospital, White 270, 55 Fruit Street, Boston, MA 02114. e-mail: mblake2{at}partners.org
Editor:
We read with great interest the article by Dr Szolar and colleagues in the February 2005 issue of Radiology (1), which retrospectively assessed adrenal gland attenuation and the percentage loss of adrenal gland contrast enhancement at computed tomography (CT) in patients with adrenocortical carcinomas and pheochromocytomas and compared these data with those in patients with adenomas and metastases. We congratulate the authors on their impressive report of CT features of 11 proved adrenocortical carcinomas, 17 pheochromocytomas, 23 adrenal adenomas, and 16 metastases to the adrenal gland (1). They found that mean attenuation of adenomas was significantly lower than those of adrenocortical carcinomas, pheochromocytomas, and metastases on unenhanced CT studies. In addition, loss of contrast enhancement on 10-minute delayed CT images in patients with adrenocortical carcinomas and pheochromocytomas was similar to that in adrenal metastases but was substantially less than that in adrenal adenomas.
We agree with Dr Szolar and colleagues that very few data on either the attenuation or the loss of contrast enhancement in adrenocortical carcinomas and pheochromocytomas have been published. However, we wish to inform the authors and readers of Radiology about a prior report of pheochromocytomas in the pathology literature (2), with lipid degeneration with massive accumulation of lipid in the cytoplasm of clear cells in the tumors. Although CT scanning was not performed in this study, this phenomenon could result in low-attenuation (<10 HU) adrenal pheochromocytomas. Indeed, we have reported (3) that while most pheochromocytomas have an attenuation of greater than 10 HU, they rarely do contain sufficient intracellular fat to have an attenuation of less than 10 HU. Our study (3) comprised nine patients with pheochromocytoma syndromes (with pathologic proof) who underwent CT scanning. Of the nine patients with pheochromocytoma syndrome, two had adrenal lesions with CT attenuation values of less than 10 HU. Of these two patients, one had an adrenal pheochromocytoma and the other had nodular medullary hyperplasia, which is a known precursor of pheochromocytoma. Therefore, we believe that the presence of a low-attenuation adrenal lesion (<10 HU), particularly in patients in whom there is strong clinical suspicion of pheochromocytoma, does not entirely exclude the possibility of pheochromocytoma.
Likewise, in these two patients with low-attenuation pheochromocytoma and nodular medullary hyperplasia, we also found more than 60% washout on delayed CT images obtained after a 10-minute interval following administration of contrast media (3). These findings are in contradistinction with those reported by Dr Szolar and colleagues, who reported less than 60% washout in all their patients with pheochromocytoma (1). In this regard it is also important to note that, to the best of our knowledge, no report of adrenal pheochromocytoma with an attenuation value higher than 10 HU but with greater than 60% washout at delayed CT scanning has been published. Perhaps rapid contrast media washout in pheochromocytoma is associated with rich lipid content, although at present this is merely speculation.
In conclusion, we agree with Dr Szolar and colleagues that most adrenal pheochromocytomas have attenuation values higher than 10 HU and less than 60% washout at delayed CT scanning. Indeed, most pheochromocytomas have contrast enhancement loss that is similar to that of adrenal metastases and significantly less than that of adrenal adenomas (3,4). However in patients with strong clinical suspicion of pheochromocytoma, adrenal pheochromocytoma cannot be entirely excluded from the list of differential diagnoses of adrenal neoplasms with an attenuation value of less than 10 HU and greater than 60% washout at delayed scanning.
References
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