CLINICAL IMAGING 1992;16:121-124

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RETROPERITONEAL SCHWANNOMAS SIMULATING ADRENAL TUMORS SOYA MAESHIMA, MD, HIRONOBU NAKAMURA, MD, MASANORI NISHIKAWA, MD, TAKAMICHI MURAKAMI, TAKASHI MITANI, MD, TAR0 MARUKAWA, MD, SHINICHI HORI, MD, TAKAHIRO KOZUKA, MD, AND MASAHIRO IRIMOTO, MD Tumors in the area of the adrenal were detected by chance in two patients who underwent a regular physical check-up. On arteriography the tumors were found to be fed by the adrenal artery. The diagnosis was retroperitoneal schwannoma, but in both patients it was difficult to differentiate the schwannoma from an adrenal tumor preoperatively. KEY WORDS:

Adrenal

tumors;

Retroperitoneal

tumors;

Schwannoma

We have recently seen two patients with benign retroperitoneal schwannomas. Both tumors were difficult to differentiate from adrenal tumors either on computed tomography (CT] and angiography posing an interesting differential diagnosis. PATIENT 1 The patient was a 60-year-old woman who underwent a screening ultrasonography as part of a regular check-up, and later had a more detailed examination based on the screening findings. Blood biochemistry and endocrine laboratory tests were all normal. On admission to the hospital, ultrasonography

From the Department of Radiology, Osaka University School of Medicine (SM., H.N., M.N., T.M., T.M., T.M., S.H., T.K.), Osaka, Japan, and the Department of Radiology, Juntendo University School of Medicine (ML), Japan. Address reprint requests to: Hironobu Nakamura, MD, Department of Radiology, Osaka University School of Medicine, l-l-50, Fukushima, Fukushima-ku, Osaka 553, Japan. Received August 1991; revised September 1991. 0 1992 by Elsevier Science Publishing Co., Inc. 655 Avenue of the Americas, 0899-7071/92/$5.00

New York, NY 10010

MD,

showed a hypoechoic mass with an internal echogenie region superior to the right kidney. Intravenous pyelogram (IVP) demonstrated a 5 x 5 cm mass at the same site, depressing the kidney. The mass was of homogeneous density, and there was no evidence of calcification. CT without enhancement showed a 6 x 4 cm low-density mass with a sharp border on the dorsal side of the right hepatic lobe. Slight enhancement of the whole mass occurred on contrast CT, but with some heterogeneity (Figure 1). Abdominal aortic angiography showed slight staining superior to the right kidney. The selective middle adrenal arteriography demonstrated hyperplasia of tumor vessels and tumor staining with a sharp border (Figure 2). These findings suggested a nonfunctioning tumor in the right adrenal, and subsequently the mass was resected. The resected mass measured 6 x 5 x 4 cm and was covered with a thin capsule. There was normal adrenal tissue superior to the mass (Figure 3). On cross section the mass was yellowish, partly hemorrhagic, and necrotic. Histologically, the mass was covered with a thin capsule. There were two distinct regions. One was Anthony A type with spindle shape cells in palisade arrangement, and the other was Antony B type with tumor cell scattering. Based on these results, a diagnosis of benign schwannoma was made.

PATIENT 2 The patient was a 50-year-old man. Ultrasonography during a regular check-up showed what was thought to be an adrenal mass. The blood biochemical and endocrine laboratory tests were normal. Abdominal CT showed a mass 5 x 4 cm with a sharp margin medial and dorsal to the right hepatic lobe. The mass

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FIGURE 1. Contrast-enhanced CT of Patient 1. There is a low-density mass in the right adrenal region. The mass was most slightly enhanced.

was of nonhomogeneous density with accompanying calcification. Contrast CT failed to enhance the core of the mass (Figure 4). A right renal arteriography showed that the kidney was compressed and displaced downward. Angiography of the inferior phrenic artery arising from the

FIGURE 2. Right middle adrenal arteriography in Patient 1. Fine neovascularity in the tumor. The normal adrenal cannot be identified.

FIGURE 3. Resected tumor from Patient 1. There is normal adrenal tissue on the top of the tumor, which could be easily detached from the mass.

right renal artery visualized three adrenal arteries and light tumor staining also arising from the inferior phrenic artery (Figure 5). At the top of the mass, normal adrenal tissue was visualized. The differential diagnosis was that of a retroperitoneal tumor or an adrenal tumor extended extraadrenally. FIGURE 4. Contrast-enhanced CT of Patient 2. A mass with calcification is seen in the medioposterior region of the right hepatic lobe. The center of the mass was not enhanced by the contrast medium.

APRIL-IUNE

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I)IFFERENTIATION

6. Resected tumor mass from Patient 2. The adrenal has extended outside the tumor capsule. The center of the tumor was cystic.

FIGURE

FIGURE 5. Inferior phrenic arteriography. Three adrenal arteries are visualized. A hypovascular minimally stained mass is present distal to the parenchyma of the normal adrenal.

The mass was resected and measured 6 x 5 x 4 It was covered with a thick capsule [Figure 6). Tumor tissue that had extended outside the capsule was resected en bloc. On cross-section, the tumor was yellowish, with a cystic core with accompanying calcification and necrosis. Histology showed benign schwannoma mainly of Antony B type. cm.

DISCUSSION Schwannoma has a reported incidence of between retroperitoneal 0.5% (1) and 1.2% (2) of all benign tumors, making it relatively rare. It originates from Schwann cells from the central and peripheral nerves, commonly developing from the peripheral nerves. Single capsulated lesions with clear-cut borders are most common. There are two histological types. Type A with spindle-shaped cells in palisade arrangement, and Type B with tumor cell scattering

often with accompanying cyst formation. There is, however, overlap of these two types. These two cases illustrate the difficult problem of differentiating, by CT or ultrasound, Schwannomas that arise at or around the site of the adrenal glands. This also may be difficult on arteriography if parasitic blood supply from the adrenal gland occurs (3, 4, 5) as it did in these two cases. In recent years more tumors have been found incidentally because of advanced diagnostic imaging, particularly by CT (6). When diagnosing these cases, the possibility of retroperitoneal schwannoma rather than an adrenal mass should be considered.

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graphic patterns of the primary retroperitoneal tumors. The role of the lumber arteries. Radiology 1972;104:259-268. 4. Levin DC, Watson RC, Baltaxe HA. Arteriography toneal masses. Radiology 1973;108:543-551. 5. Damascelli

B, Musumeci

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R, Botturi M, Retrillo R, Spagnoli 1.

Angiography 570.

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AJR 1975;124:565-

6. Belldegrum A, Hussain S, Seltzer SE, Loughlin KR, Gittes RF, Richie JP. Incidentally discovered mass of the adrenal gland. Surg Gynecol Obstet 1986;163:203-208.

Retroperitoneal schwannomas simulating adrenal tumors.

Tumors in the area of the adrenal were detected by chance in two patients who underwent a regular physical check-up. On arteriography the tumors were ...
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