Abstract. We present a case of adrenal metastasis from clear-cell renal cell carcinoma in which presence of a small amount of fat was shown on chemical shift ...
Abdom Imaging 26:439 – 442 (2001) DOI: 10.1007/s002610000176
Abdominal Imaging © Springer-Verlag New York Inc. 2001
Metastatic adrenal tumor from clear-cell renal cell carcinoma: a pitfall of chemical shift MR imaging K. Shinozaki,1 K. Yoshimitsu,1 H. Honda,1 T. Kuroiwa,1 H. Irie,1 H. Aibe,1 S. Naito,2 T. Migita,3 Y. Asayama,3 K. Masuda1 1
Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan 2 Department of Urology, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan 3 Department of Pathology II, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan Received: 16 May 2000/Accepted after revision: 13 September 2000
Abstract We present a case of adrenal metastasis from clear-cell renal cell carcinoma in which presence of a small amount of fat was shown on chemical shift gradient-echo magnetic resonance imaging. Radiologists should be aware that signal loss of the adrenal tumor on out-of-phase gradient-echo images does not always suggest the diagnosis of benign adenoma, particularly in patients with a history of renal cell carcinoma. Key words: Adrenal gland—Metastasis—Renal cell carcinoma—Clear-cell type—MRI—Chemical shift imaging.
Chemical shift imaging (CSI) has been shown to be a sensitive method in detecting small amounts of fat [1– 8]. The usefulness of this technique in differentiating benign from malignant adrenal masses has been reported and established [1– 4] and is based on the fact that adrenal adenoma usually consists of lipid-containing cells, whereas metastasis, adrenocortical carcinoma, and pheochromocytomas generally show no such lipid accumulation [2, 3]. This technique has also been applied to detect cytoplasmic fat in renal cell carcinoma (RCC) of clear-cell type, which is the most common cell type of RCC [5, 6]. Thus, there is a risk that CSI may not differentiate adrenal adenoma from metastasis from clear-cell RCC because both contain small amounts of fat [6]. To our knowledge, there is no report distinguishing adrenal metastasis from RCC in which CSI suggested the presence of intratumoral fat. We present such a case, where
Correspondence to: K. Shinozaki
CSI demonstrated the presence of fat in the adrenal mass, leading to the histologic diagnosis of metastatic RCC.
Case report A 60-year-old man was referred to our institution for evaluation and treatment of a right adrenal mass. He had undergone a left nephrectomy 8 years previously because of RCC, the histological type of which was clear cell. Routine follow-up computed tomography (CT) showed a hypervascular right adrenal mass measuring 2.0 cm in diameter behind the inferior vena cava (Fig. 1). Magnetic resonance imaging (MRI; 1.5 T, Magnetom Vision, Siemens, Germany) was performed to characterize the tumor. The signal intensities of the tumor on T1- and T2-weighted images were similar and higher, respectively, in relation to the right renal cortex (Fig. 2A,B). CSI showed appreciable loss of signal intensity of the tumor on out-of-phase as opposed to in-phase images, and this loss was confirmed by subtraction images (Fig. 3A– C). This signal loss was also confirmed quantitatively by measuring the signal intensity of the tumor by using the normal renal cortex as reference tissue; the signal–loss ratio [7] was calculated to be 0.14, suggesting the presence of fat [5, 7]. On early-phase dynamic images after intravenous administration of Gd-DTPA, the tumor demonstrated marked enhancement on the early-phase image and slow washout on the delayed-phase image. Although CSI suggested the presence of fat in the tumor, its marked vascularity and clinical information
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Fig. 1. Early phase of contrast-enhanced abdominal CT shows hypervascular right adrenal mass (arrow). Fig. 2. A T1-weighted image using FLASH sequence (TR/TE/FA/NEX ⫽ 135.5/4.2/90/1) shows well-circumscribed mass (arrow). B Transaxial turbo spin-echo T2-weighted image (TR/TE/ETL/NEX ⫽ 4275/138/29/1) shows a high-signal-intensity right adrenal mass (arrow).
favored the diagnosis of metastasic adrenal tumor. Right adrenectomy was performed, and the resected specimen showed clear cells proliferating in alveolar or glandular fashion, suggesting metastasis from the previously resected clear-cell RCC (Fig. 4).
K. Shinozaki et al.: Adrenal metastasis from clear-cell RCC
Fig. 3. A, B Transaxial chemical shift gradient-echo images through the mass (arrows). Note the significant signal reduction of the tumor in relation to the renal cortex on out-of-phase (A, TR/TE/FA/NEX ⫽ 135/2.3/70/1) versus in-phase (B, TR/TE/FA/NEX ⫽ 135/4.7/70/1) images. C Subtraction image shows apparent hyperintensity (arrow).
Discussion CSI is useful in the differential diagnosis of adrenal masses [1– 4, 9] primarily because it can detect fat in adrenal adenomas, which is the most common type of
K. Shinozaki et al.: Adrenal metastasis from clear-cell RCC
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Fig. 4. Microphotography of the mass shows clear cells proliferating in an alveolar or glandular fashion. The feature is essentially the same as clear-cell RCC previously resected. Original magnification, 400⫻; hematoxylin and eosin stain.
adrenal tumor. The diagnostic accuracy of this technique has been reported to be 80 –100% [2, 4]. CSI has been applied in the diagnosis of other fatcontaining tumors, including clear-cell RCC, granularcell RCC with macrophagic infiltration, and hepatocellular carcinomas with fatty metamorphosis [5– 8]. Collision tumors in the adrenal gland represent a metastatic lesion, and lipid is associated with a simultaneous adenoma. CSI has been able to characterize the separate components of these tumors: the adenomatous component shows a decrease in signal intensity on out-of-phase images, whereas the metastatic component does not [10]. Outwater et al. [6] suggested that clear-cell RCC metastasis in the adrenal gland might be confused with adrenal adenoma on CSI because both lesions contain fat. Because RCC commonly involves the adrenal gland [11] and clear-cell RCC is the most common cell type, accounting for 40 – 60% of all RCCs [12], differentiation between these two conditions would be of great clinical importance. Mitchell et al. [3] and Tsushima et al. [2] proposed indices of their own to differentiate adenomas from nonadenomas, with their negative values indicating the diagnosis of adenoma. However, in the present case, these indices of the adrenal mass were calculated as ⫺14.5% and ⫺9.8%, respectively, which erroneously suggests the diagnosis of adenoma. To the best of our knowledge, there has been no report in the radiologic literature regarding adrenal metastasis from RCC in which CSI suggested the presence of intratumoral fat. Krestin et al. [13] reported the usefulness of dynamic MRI, with an accuracy of 91%, in the differential diagnosis of adrenal masses. According to those results, nonadenomas demonstrate early pronounced enhancement and delayed washout, and adenomas demonstrate mild
enhancement and rapid washout. Although these results have not been supported completely by other studies [9, 14], the marked vascularity of the adrenal mass in the present case favored the diagnosis of metastasis rather than adenoma. In conclusion, radiologists should not depend solely on CSI in diagnosing adrenal tumors. Findings on other imaging modalities, including dynamic CT or dynamic MRI, should be considered, particularly when the patient has a history of RCC or other malignant disease where the tumors contain fat. Otherwise, with no evidence of primary malignancy with a lipid content, the MRI findings would suggest an adenoma.
References 1. Outwater EK, Siegelman ES, Radecki PD, et al. Distinction between benign and malignant adrenal masses: value of T1-weighted chemical-shift MR imaging. AJR 1995;165:579 –583 2. Tsushima Y, Ishikawa H, Matsumoto M, et al. Adrenal masses: differentiation with chemical shift, fast low-angle shot MR imaging. Radiology 1993;186:705–709 3. Mitchell DG, Crovello M, Matteucci T, et al. Benign adrenocortical masses: diagnosis with chemical shift MR imaging. Radiology 1992;185:345–351 4. Heinz-Peer G, Honigschnabl S, Schneider B, et al. Characterization of adrenal masses using MR imaging with histopathologic correlation. AJR 1999;173:15–22 5. Yoshimitsu K, Honda H, Kuroiwa T, et al. MR detection of cytoplasmic fat in clear cell renal cell carcinoma utilizing chemical shift gradient echo imaging. J Magn Reson Imaging 1999;9:579 –585 6. Outwater EK, Bhatia M, Siegelman ES, et al. Lipid in renal clear cell carcinoma: detection on opposed-phase gradient-echo MR images. Radiology 1997;205:103–107 7. Yoshimitsu K, Honda H, Kuroiwa T, et al. Fat detection in granularcell renal cell carcinoma using chemical shift gradient-echo MR
442 imaging: another renal tumor that contains fat. Abdom Imaging 2000;25:100 –102 8. Martin J, Sentis M, Zidan A, et al. Fatty metamorphosis of hepatocellular carcinoma: detection with chemical shift gradient-echo MR imaging. Radiology 1995;195:125–130 9. Korobkin M, Lombardi TJ, Aisen AM, et al. Characterization of adrenal masses with chemical shift and gadolinium-enhanced MR imaging. Radiology 1995;197:411– 418 10. Schwarz LH, Macari M, Huvos AG, et al. Collision tumors of the adrenal gland: demonstration and characterization at MR imaging. Radiology 1996;201:757–760
K. Shinozaki et al.: Adrenal metastasis from clear-cell RCC 11. Abrams HL, Spiro R, Goldstein N. Metastases in carcinoma: analysis of 1000 autopsied cases. Cancer 1950;3:74 – 85 12. Thoenes W, Strorkel S, Rumpelt HJ. Histopathology and classification of renal cell tumors (adenomas, oncocytomas and carcinomas). Pathol Res Pract 1986;181:125–143 13. Krestin GP, Steinbrich W, Fredmann G, et al. Adrenal masses: evaluation with fast gradient-echo MR imaging and Gd-DTPA– enhanced dynamic studies. Radiology 1989;171:675– 680 14. Rening JW, Stutley JE, Leonhardt CM, et al. Differentiation of adrenal masses with MR imaging: comparison of techniques. Radiology 1994;192:41– 46
