Differentiation of Adrenal Adenoma and Nonadenoma in Unenhanced CT: New Optimal Threshold Value and the Usefulness of Size Criteria for Differentiation

OBJECTIVE: To determine the optimal threshold for the attenuation values in unenhanced computed tomography (CT) and assess the value of the size criteria for differentiating between an adrenal adenoma and a nonadenoma. MATERIALS AND METHODS: The unenhanced CT images of 45 patients at our institution, who underwent a surgical resection of an adrenal masses between January 2001 and July 2005, were retrospectively reviewed. Forty-five adrenal masses included 25 cortical adenomas, 12 pheochromocytomas, three lymphomas, and five metastases confirmed by pathology were examined. The CT images were obtained at a slice thickness of 2 mm to 3 mm. The mAs were varied from 100 to 160 and 200 to 280, while the 120 KVp was maintained in all cases. The mean attenuation values of an adrenal adenoma and nonadenoma were compared using an unpaired t test. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy at thresholds of 10 HU, 20 HU, and 25 HU were compared. The diagnostic accuracy according to the size criteria from 2 cm to 6 cm was also compared. RESULTS: The twenty-five adenomas showed significantly lower (p 90% but a specificity < 70%. Size criteria of 2 or 3 cm had a high specificity of 100% and 80% but a low sensitivity of 20% and 60%. CONCLUSION: The threshold attenuation values of 20 or 25 HU in the unenhanced CT appear optimal for discriminating an adrenal adenoma from a nonadenoma. The size criteria are of little value in differentiating adrenal masses because of their low specificity or low sensitivity.

Spontaneous Rupture of Adrenal Metastasis from Hepatocellular Carcinoma

Rupture of adrenal tumor from various primary origins is a rather rare event. We report here on a ruptured adrenal metastasis from hepatocellular carcinoma, and this ruptured metastasis was observed at the time of the initial diagnosis.

Usefulness of Percentage Enhancement Washout Value Calculated on Unenhanced, Contrast-Enhanced, and Delayed Enhanced CT in Adrenal Masses: Adenoma versus Metastasis

PURPOSE: To determine the usefulness of percentage enhancement washout value calculated on unenhanced, enhanced and delayed enhanced CT scans for the characterization of adrenal masses. MATERIALS AND METHODS: Forty adrenal masses less than 5 cm in size were assessed using a protocol consisting of unenhanced CT, enhanced CT 60 seconds after intravenous administration of contrast material, and delayed enhanced CT at 10 minutes. The CT attenuation value of adrenal tumors was estimated on each scan, and percentage enhancement washout value was calculated as follows: [(attenuation value at enhanced CT-attenuation value at delayed CT)/ (attenuation value at enhanced CT-attenuation value at unenhanced CT)x100]. An adrenal mass was considered benign if its percentage enhancement washout value was at the threshold value, set to 60% and 50%, or higher. The accuracy of the procedure was determined by comparing its findings withthe final clinical diagnosis. RESULTS: Twenty-nine massess were benign and 11 were malignant. The mean percentage enhancement washout value of the former was significantly higher than that of the latter (66.7% vs. 21.8%; p<0.01). All adenomas except one had a washout value of more than 50%. With a percentage washout threshold of 60%, 35 of 40 lesions were correctly characterized as benign or malignant [sensitivity 82.7% (24/29), specificity 100% (11/11), accuracy 87.5% (35/40)]; with a threshold of 50%, 39 of 40 lesions were correctly characterized [(sensitivity 96.5% (28/29), specificity 100% (11/11), accuracy 97.5% (39/40)]. CONCLUSION: Percentage enhancement washout values are useful for characterizing an adrenal mass as benign or malignant. For characterization, a threshold value of 50% was more accurate than one of 60%.

Solitary Fibrous Tumor of the Adrenal Gland: A Case Report

Solitary fibrous tumor is a rare mesenchymal tumor, usually involving the pleura. Its occurrence in various organs of the body has recently been described; in particular, two cases of solitary fibrous tumor of the adrenal gland have been reported worldwide, but no case has been reported in Korea. We describe a case of solitary fibrous tumor occurring in the left adrenal gland and discovered incidentally at CT.

Adrenal Collision Tumor Consisted of Adrenocortical Carcinoma and Myelolipoma: A Case Report

The identification of fat density by unenhanced CT within an adrenal mass is highly suggestive of myelolipoma. Adrenal collision tumors which involve a myelolipoma are uncommon, though the involvement of adenomas and pheochromocytomas has been reported. We describe a case in which an adrenal collision tumor consisting of an adrenocortical carcinoma and myelolipoma, presented as a large fat-containing adrenal soft tissue mass.

Radiological Findings of Congenital Lipoid Adrenal Hyperplasia: A Case Report

Congenital lipoid adrenal hyperplasia (CLAH) is a rare autosomal recessive disorder characterized by the marked accumulation of lipids and cholesterol in the adrenal cortex, and the failure of adrenal steroids to synthesise. We report the ultrasound (US), computed tomographic (CT), and magnetic resonance (MR) imaging findings in a four-day- old female neonate with CLAH.

Prenatally Diagnosed Cystic Neuroblastoma: A Case Report

Cystic masses of the adrenal gland are unusual in the fetus and most are secondary to hemorrhage. Cysticneuroblastoma is extremely rare, and in contrast to solid neuroblastoma, follows a benign course, is diagnosedearlier, and rarely presents with metastatic lesions(1-4). We report one case of cystic neuroblastoma diagnosedprenatally by ultrasound(US) and magnetic resonance(MR) imaging, and include a review of the literature.

CT Differentiation of Adrenal Pheochromocytoma from Primary Carcinoma and Metastasis

PURPOSE: To evaluate the efficacy of CT imaging in differentiating pheochromocytoma from primary adrenalcarcinoma and metastasis. MATERIALS AND METHODS: The authors retrospectively reviewed CT imagings of 24 patients(9 males, 15 females, mean age 49) with 27 surgically or clinically proven adrenal neoplasms larger than 3cm indiameter. These neoplasms included pheochromocytomas(n=11), adrenal carcinomas(n=6), and adrenal metastases(n=10,bilateral : 3). Two radiologists visually inspected CT features with respect to tumor size, shape, intratumoral hypodensity, and calcification, and agreed upon their evalvation. These results were compared with the final histopathologic and clinical diagnosis. RESULTS: Ten of eleven pheochromocytomas(91%) were observed to be round or ovoid; this shape was rarely seen in primary carcinomas(0/6) or metastases(2/10). in contrast, mostcarcinomas(6/6, 100%) were lobulated or irregular in shape, as were most metastases(8/10, 80%). smooth, round orovoid intratumoral hypodensity was noted in all pheochromocytomas. Stellate or linear, irregular intratumoral hypodensity was present in all carcinomas and metastases. However, there were no significant differences in CTdensity of calcification. CONCLUSION: Tumor shape and intratumoral hypodensity are very useful CT findings for differentiating adrenal pheochromocytomas from primary carcinomas and metastases.