Korean J Urol Oncol 2010;8(3):152-155

Primary of the Pelvic Region

Ok Ran Shin1, Yun Seok Jung2, Myung Sun Choi2, Chang Hee Han2, Sung Hak Kang2, Yong Seok Lee2 Department of 1Hospital Pathology, 2Urology, College of Medicine, The Catholic University of Korea, Seoul, Korea

Angiomyolipoma (AML) is a that is composed of adipose tissue, blood vessels and . The is the most commonly affected organ. The incidence of AML is about 0.3-3% in the general population. AML is sometimes associated with . Although rare, extrarenal AML has been reported to occur in other organs such as the liver, heart & mediastinum, spermatic cord, vaginal wall, and oral cavity. Primary AML in the pelvic region has very rarely been reported in the literature. Moreover, AML containing calcification is even rarer. A 61-year-old man was admitted to our hospital with a mass in the lower abdomen for 3 months. Open surgical excision was performed and the histopathological examination revealed AML. A one year postoperative follow-up showed no remarkable findings. (Korean J Urol Oncol 2010;8:152-155) 󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏 Key Words: Angiomyolipoma, Pelvis, Calcification

AML is histopathologically classified as a benign tumor that palpation. The laboratory tests, including CBC, blood-chemistry consists of the smooth muscle cells, mature adipocytes and and urinalysis, were all normal. blood vessels. The incidence of AML is about 0.3-3% in the A computed tomography (CT) scan was subsequently per- general population.1 In most cases it occurs in the kidney, formed. The non-enhanced CT showed a large, 8.5x8.6x8.7cm, sometimes associated with tuberous sclerosis. Extrarenal AML heterogenous mass with calcification and fat density has been rarely reported to occur in other organs such as liver, (Hounsfield unit of -40) in the pelvic region (Fig. 1). Upon con- heart & mediastinum, spermatic cord, vaginal wall, and oral trast-enhanced CT, no abnormal lymph nodes were found near cavity, etc.1 We report here a case of primary pelvic AML, no- the mass. table for calcifications. Pelvic MRI was performed to better analyze the specific structures of the surrounding the mass. The axial CASE REPORT T1-weighted image showed a diffuse heterogenous low-sig- nal-intensity, extraperitoneal paravesical mass that had focal in- A 61-year-old man was admitted to our hospital with a mass termediate-signal-intensity lesions (Fig. 2). The axial T2-weighted in the lower abdomen for the previous 3 months. His past medi- image revealed a diffuse intermediate-signal-intensity, extra- cal and family history were non-contributory. On physical ex- peritoneal, paravesical mass and focal high-signal-intensity le- am, he had normal vital signs and normal exam of the scrotum sions resembling fluid, as well as low signal intensity lesions and testes. However, a 10x9cm ovoid mass was palpable in the resembling calcifications within the mass. lower abdomen. It was firm and without tenderness to Based on these findings, we performed open surgery, with an initial impression of a or teratoma. Although Received November 1, 2010, Revised November 18, 2010 (1st), it was large and had extensive adhesions to the pubic bone and December 2, 2010 (2nd), Accepted December 3, 2010 Corresponding Author: Yong Seok Lee, Department of Urology, the symphysis, we were able to remove the mass successfully. Uijongbu St. Mary’s Hospital, The Catholic University of Gross exam of the excision specimen included a size of Korea College of Medicine, 65-1, Keumoh-dong, Uijongbu 11.4x9.5x6.0cm, pale to dark brownish color, and ovoid shape 480-717, Korea. Tel: 82-31-820-3588, Fax: 82-31-847-6133, E-mail: [email protected] with rough surface. It was relatively firm and tensional. The 152 Ok Ran Shin, et al：Pelvic Angiomyolipoma 153

Fig. 1. The non-enhanced CT shows a heterogenous huge mass Fig. 3. The microscopic findings show proliferation of thick wal- with calcification and fat density foci in the pelvic region. led blood vessels, mature adipocytes and smooth muscle cells (H&E stain, x40).

Fig. 2. The axial T1-weighted image shows a diffuse, hetero- Fig. 4. Immunohistochemical staining shows the proliferating genous, low signal intensity, extraperitoneal, paravesical mass that smooth muscle cells are positive for actin (actin stain, x400). has focal intermediate signal intensity lesions. was discharged without complications in 7 days. A one year cross-section surface of the tumor showed marked hemorrhage follow-up had no remarkable findings. and necrosis. Microscopic findings showed diffuse hemorrhagic necrosis and marked fibrosis throughout the specimen, making DISCUSSION the pathological diagnosis challenging. Abundant adipose tis- sue, blood vessels and smooth muscle cells were found in the Extrarenal AML is an uncommon entity. The liver viable tissue that partially remained at the margin of the speci- and uterus appear to be the most common locations.2 Extrarenal men (Fig. 3). Bone formation and calcification were noted in retroperitoneal AMLs are rare and result in a high incidence some parts of the mass. Immunohistochemical stain was done of hemorrhagic than renal AML. Various methods are to confirm the presence of smooth muscle cells, and the pro- used to diagnose AML, but angiography was the most wide- liferating smooth muscle cells were positive for actin. These ly-used modality in the past. The advances of magnetic reso- histopathological findings are consistent with AML (Fig. 4). nance imaging (MRI) made remarkable contribution to evalua- The patient had an unremarkable postoperative course, and tion of the cardiovascular system and vascular malformations. 154 대한비뇨기종양학회지：제8권 제3호 2010

Due to its superior contrast resolution and sensitivity, MRI is deemed to be a benign due to the lack of mitosis able to differentiate between fat, muscle, bone and vascular and negative findings of ki-67. AML in the urogenital system structures. It provides three-dimensional information without is one of the benign neoplastic , which can still cause the use of ionizing radiation or invasive procedures. On MRI, significant morbidity from hemorrhage. , endo- AMLs with fat typically demonstrate high signal intensity on scopic intervention or surgical removal have all been performed the T1- and T2-weighted imgages.3 In our case, the tumor was as alleviating options.9 In our case, there was no microscopic located in the extraperitoneal paravesical pelvic cavity. MRI did or macroscopic hematuria because the AML did not occur with- not show findings typical for AML, but rather suspicious for in the urogenital system itself. It should be noted, however, that fibrosarcoma or teratoma in the pelvic cavity. In retrospect, we the location of the mass, i.e. adjacent to the bladder in the pel- suspect that the intratumoral hemorrhage, extensive hyaliniza- vic cavity, has relative significance to the urogenital system. tion and liquefaction of the mass hindered detection of the typi- Unlike renal AML that tends to recur and locally invade cal findings of AML. Moreover, the mass was accompanied lymph nodes, close observation is usually sufficient for un- with dystrophic calcifications. Although hemorrhage is a fre- complicated extrarenal AML. Surgical removal is warranted quent complication, necrosis and calcifications are rare in when the mass is large, and it is relative easy to do so, because AML. Osseous metaplasia associated with a fibrous scar can this tumor is well-defined in the majority of cases. If there are be an explanation for the calcifications in our case. There are difficulties or contraindiations of surgical option, more con- four cases reported so far on of AML showing bone formation, servative treatments, e.g. embolization, can be considered.10 and all of them originated from the kidneys.4 Teratomas are tu- Open surgical removal was performed in our case, because of mors that usually arise from one or more of the three cell-lines, its large size within the lower abdomen, which was affecting i.e. endoderm, mesoderm, and ectoderm. The tumor in our case the with its mass-effect on the adjacent bladder. displays mesodermal structures with various components, but Histopathological evaluation of this large mass established the is not a teratoma. diagnosis of AML, but we could not specify its origin. Gross exam of a typical AML shows tan brown to grayish When a large proliferating mass is accompanied with calcifi- white, variegated surface with hemorrhagic or necrotic tissue. cation, and it is found in the pelvic cavity, the possibility of Histopathologically, AML is composed of varying amounts of a malignant neoplasm should be ruled out. However, differ- the smooth muscle cells, adipose tissue and blood vessels. ential diagnosis should include AML and aggressive surgical There are various kinds of blood vessels in AML such as capil- treatment is necessary, when it is accompanied with intra- laries, arterioles and medium-sized muscular arteries. The tumoral hemorrhage, hyalinization and liquefaction. smooth muscle cells usually surround blood vessels or they are in the form of an inconspicuous mass. Alternatively, they can REFERENCES be entangled with each other, independent of blood vessels.5 Most of the adipose tissue is composed of mature lipocytes, 1. Jahn H, Nissen HM. 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