Extrarenal retroperitoneal angiomyolipoma:
case report and review of the literature
C.-A. Tseng,
1Y.-S. Pan,
2Y.-C. Su,
2D.-C. Wu,
2C.-M. Jan,
2W.-M. Wang
21Division of Gastroenterology, Department of Internal Medicine, Buddhist Tzu Chi General Hospital, Dalin, Chia-Yi, Taiwan, People’s Republic of China
2Division of Gastroenterology, Department of Internal Medicine, Kaohsiung Medical University Hospital, 100 Shih-Chuan 1st Road, Kaohsiung 807, Taiwan, People’s Republic of China
Abstract
Angiomyolipomas are rare benign tumors that usually occur in the kidneys. Extrarenal angiomyolipomas are extremely uncommon. We describe a case of angiomyolipoma arising in the retroperitoneum that was successfully treated by arte-rial embolization and surgical excision. The literature on retroperitoneal extrarenal angiomyolipoma and its differen-tial diagnoses is briefly reviewed.
Key words: Angiomyolipoma—Retroperitoneum— Fatty—Tumor—Angiography
Case report
A 35-year-old Chinese woman who was otherwise healthy visited our hospital (Kaohsiung Medical University Hospi-tal) in October 2002 because of gradually increasing abdom-inal girth and abdomabdom-inal fullness during the previous year. Physical examination showed a large, smooth, nontender, and immovable mass in the right abdomen. It was palpable from the right costal margin to the right anterior superior iliac spine and extended beyond the midline of the abdomen. The results of laboratory examination, including a differen-tial blood cell count and biochemistry, were within normal limits, except for an elevation of lactate dehydrogenase (647
/L; normal range, 180–460 /L). Ultrasonography showed
a large hyperechoic tumor mass. Computed tomography (CT) disclosed a huge (20 ⫻ 9 ⫻ 22 cm) retroperitoneal mass displacing the right kidney ventrally. The mass was composed of fatty tissue and hypervascularity (Fig. 1). The abdominal aortogram and selective angiograms of the celiac artery, superior mesenteric artery, right lumbar artery, and right renal artery showed a large hypervascular tumor arising from the right lumbar artery (Fig. 2A) and branches of the right renal artery (Fig. 2B).
Because the tumor was hypervascular, we considered transarterial embolization before surgery. The lumbar artery feeding the tumor was successfully embolized with Gelfoam pledget and metallic coils. The right renal artery was difficult to approach.
During surgery, a huge, well-encapsulated retroperitoneal mass was found, which had displaced the right kidney to the left upper quadrant area and occupied the entire right side of abdomen. The tumor was easily dissected from the right kidney and surrounding tissues; the resected tumor weighed 2800 g, with dimensions of 23⫻ 22.5 ⫻ 7.2 cm. The tumor was encapsulated, gray-white, and firm (Fig. 3). Microscop-ically, it was found to be an angiomyolipoma, composed mostly of mature adipose tissues, numerous blood vessels, and proliferative smooth muscle. Immunohistochemically, the proliferative smooth muscle cells were positive for
␣-smooth muscle actin (␣-superior mesenteric artery), the
Correspondence to: W.-M. Wang; email: [email protected]
Fig. 1. Contrast-enhanced CT of the abdomen demonstrates
a huge retroperitoneal fatty mass filling the entire abdomen. The right kidney (K) is displaced ventrally. Note the rich vascularity of the tumor (arrows).
A
bdominal
I
maging
© Springer Science⫹Business Media, Inc., 2004
Received: 11 December 2003 / Accepted: 15 January 2004 / Published online: 8 June 2004
Abdom Imaging (2004) 29:721–723 DOI: 10.1007/s00261-004-0179-2
tumor cells were positive for S-100 protein, and the vascular component was positive for CD34. Recovery was uneventful and the patient was discharged 1 week after surgery.
Discussion
Angiomyolipoma is a rare benign soft tissue tumor that contains smooth muscle, thick-walled vessels, and mature fat and is generally involved in one or both kidneys. Extrarenal angiomyolipomas are very uncommon, and the liver is the
most common extrarenal site. Other sites reported include bone [1], colon [2], heart [3], lung [4], parotid gland [5], skin [6], spermatic cord [7], gynecologic regions [8 –10], and the retroperitoneum [11–14]. Extrarenal retroperitoneal angio-myolipoma is extremely rare to our knowledge, with no more than 10 cases having been reported in the literature.
Tuberous sclerosis sometimes occurs in patients with renal angiomyolipoma but has not been reported in patients with extrarenal angiomyolipoma, and the reasons for this are unclear. The patient described in our report had no evidence of tuberous sclerosis. Extrarenal retroperitoneal angiomyo-lipoma also has been reported to occur with early gastric cancer [12]. In our patient, gastroenteroscopy and colonos-copy were performed, disclosing superficial gastritis and external compression at the ascending and descending colon, respectively.
The radiologic differential diagnosis of retroperitoneal fatty tumors must include liposarcoma, lipoma, leiomyoma with fatty change, and angiomyolipoma. Usually, the correct diagnosis is made after laparotomy, despite numerous pre-operative imaging studies. Angiomyolipoma is usually mis-taken for liposarcoma. However, it is important to differentiate retroperitoneal angiomyolipoma from liposar-coma because liposarliposar-coma is malignant and should be treated with radical surgery. In contrast, angiomyolipoma is considered cured after tumor excision. Wang et al. [15] reported that analysis of the CT characteristics of linear vascularity, aneurysmal dilatation, bridging vessel, and the beak sign can be helpful in diagnosing retroperitoneal an-giomyolipoma, and this report was helpful in making the differential diagnosis in our case.
Fig. 2. Abdominal aortogram shows a large hypervascular tumor arising prominently from the (A) right lumbar artery and the
(B) right renal artery. The tumor vessels are tortuous (arrowheads), enlarged, and resemble a corkscrew (arrows).
Fig. 3. Gross specimen of the resected tumor. The tumor is
well encapsulated, gray-white, and firm. The dimensions are 23⫻ 22.5 ⫻ 7.2 cm.
Like renal angiomyolipoma, extrarenal retroperitoneal angiomyolipoma has a propensity to bleed, and the risk is correlated with the size of the tumor [16]. A huge tumor can be managed with selective arterial embolization to reduce intraoperative bleeding (as in our case) or to stop bleeding during emergencies [17]. In conclusion, selective arterial embolization and simple excision constitute safe and effec-tive management for extrarenal retroperitoneal angiomyoli-poma.
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