Angiomyolipoma of the kidney: report of three cases and a statistical study of 194 cases in Japan

Three cases of renal angiomyolipoma are reported. The first case was a 53-year-old female with the complaint of left flank pain. In both cases selective angiography revealed a renal tumor, and computerized tomography disclosed a renal mass with low density corresponding to the fat tissue. From several examinations these two cases were preoperatively diagnosed as renal angiomyolipoma and nephrectomy was performed. Histopathological diagnosis was renal angiomyolipoma. The third case was a 64-year-old female with the complaints of left flank pain and macrohematuria. In this case computerized tomography revealed a renal mass which did not have a low density area. The possibility of renal cell carcinoma was considered and nephrectomy was performed. Histological diagnosis was renal angiomyolipoma which was primarily composed of smooth muscle cells. The first case had a calcified lesion in the brain. But there was no evidence of tuberous sclerosis in the following two cases. Some problems in diagnosis and treatment of renal angiomyolipoma are presented, and a statistical study is made on 194 reported cases of renal angiomyolipoma in Japan.     

The limit in differential diagnosis of renal angiomyolipoma from renal cell carcinoma on computerized tomography: a case report

Recent reports have described that the accurate preoperative diagnosis of renal angiomyolipoma is possible with computerized tomography (CT). There are, however, some cases of angiomyolipoma which are indistinguishable from renal cell carcinoma on CT. Herein we report a case of renal angiomyolipoma which CT failed to reveal preoperatively. In a 71-year-old Japanese male, a left renal tumor was incidentally suspected on excretory urogram. Then CT demonstrated a homogeneous mass in the upper part of the left kidney, 6 cm in diameter, which showed a positive attenuation coefficient, slightly denser than renal parenchyma. Selective left renal arteriogram showed hypervascularity without aneurysmal formation or arteriovenous fistula. These radiologic findings strongly suggested renal cell carcinoma and radical left nephrectomy was performed. Histological examination confirmed angiomyolipoma composed mainly of smooth muscle with thick-walled vessels and immature fat cells. We reviewed the literature and discussed the computerized tomographic-pathologic correlation of angiomyolipoma.     

Juxtaglomerular cells in renal angiomyolipoma. Ultrastructural observation

We have studied a case of renal angiomyolipoma by electron microscopy and found juxtaglomerular cells with typical rhomboid and spherical granules, in addition to smooth muscle cells, fat cells, and abnormal blood vessels. To our knowledge, this is the first ultrastructural demonstration of juxtaglomerular cells in renal angiomyolipoma.     

CT对肾血管平滑肌脂肪瘤的诊断及术式选择的意义（附30例报告）

为探讨ＣＴ检查对肾血管平滑肌脂肪瘤的诊断价值及与手术方式的关系，对３０例肾血管平滑肌脂肪瘤患者的ＣＴ资料结合临床分析。结果发现：肾血管平滑肌脂肪瘤典型ＣＴ表现为瘤内同时出现肌肉、血管、脂肪三种成分的密度，肿瘤越大其软组织成分越多；肿瘤大小及生长部位与临床症状及手术方式有关。提出了本病的ＣＴ诊断分级，认为ＣＴ对本病具有重要的诊断价值，其诊断分级对临床选择手术方案有一定意义。     

Angiomyolipoma of the nasal cavity: Case report and review of the literature

An unusual localization of intranasal angiomyolipoma is described in an adult male patient with no signs of tuberous sclerosis. The lesion was composed of mature fat cells, vascular spaces with lack of elastic tissue, and presence of bundles of mature smooth muscle cells. Antibodies to intermediate filaments revealed presence of vimentin and absence of desmin in both smooth muscle bundles and in vessel walls. A review of the literature has shown that this is only the third reported case of the angiomyolipoma of the nasal cavity, and some important differences between this entity and renal angiomyolipoma are described. © 1994 John Wiley & Sons, Inc.     

Myolipoma arising from the renal capsule: a case report

A 53-year-old female visited us with an asymptomatic renal mass, which was incidentally found on abdominal ultrasonography (US). US showed a heterogeneous renal mass measuring 5 cm in diameter. Computed tomorraphy and magnetic resonance imaging showed that the tumor was mixed with muscle and fat tissue, faintly enhanced, and located at the lower portion of the left kidney. Although renal angiomyolipoma (AML) was suspected from these findings, we could not rule out a malignant tumor. Therefore, she underwent a laparoscopic partial nephrectomy. Histopathological examination revealed the tumor composed of smooth muscle and mature adipose tissue without cytological atypia arising from the renal capsule. The tumor contained no AML-like blood vessels, and was negative for HMB-45 staining. The final diagnosis was myolipoma arising from the renal capsule. Myolipoma is a rare benign neoplasm in the soft tissue of retroperitoneum and abdominal cavity. Since it is difficult to distinguish myolipoma from other benign and malignant tumors with fat tissue only by imaging studies, a surgical approach should be considered.     

Angiomyolipomas of the liver

Twelve cases of primary angiomyolipoma of the liver are presented. Histologically the tumors were similar to renal angiomyolipomas, containing tortuous blood vessels, smooth muscle, and fat. Some also contained prominent hematopoietic elements (angiomyomyelo-lipomas). The tumors may have necrosis and pleomorphic epithelioid smooth muscle cells which have led some to be mistaken for malignancies. Despite the similarity to their renal analogs, hepatic angiomyolipomas are not associated with tuberous sclerosis.     

Molecular genetic evidence for different clonal origin of components of human renal angiomyolipomas.

Renal angiomyolipoma is a benign neoplasm composed of variable proportions of blood vessels, smooth muscle, and adipose tissue. Smooth muscle, adipose tissue, blood vessels, and adjacent normal kidney tissue were separately microdissected from sections prepared from formalin-fixed, paraffin-processed tissues from angiomyolipomas from 18 women. X chromosome inactivation analysis using the methylation pattern at exon 1 of the human androgen receptor gene on chromosome Xq11-12 was used to study the clonal origin of each component. Nonrandom inactivation of X chromosomes was found in six of the 15 informative tumors. The smooth muscle and adipose tissue showed differing patterns of nonrandom inactivation of X chromosomes in five angiomyolipomas and the same pattern of nonrandom inactivation of X chromosomes in one. Samples from the blood vessels showed random inactivation of X chromosomes in all informative cases. Our data showed that the adipose tissue and smooth muscle cells of renal angiomyolipoma are both monoclonal but may arise independently. The coexistence of tumor subclones with morphologic heterogeneity can lead to the formation of a clinically detectable tumor.     

Small hyperechoic renal tumors displaying no fat content on CT.

We report two cases of small renal adenocarcinoma and one case of small angiomyolipoma, which were identified as hyperechoic tumors by ultrasonography. None of the three tumors displayed fat content on plain CT. Since CT cannot reliably identify the intratumoral structure of small hyperechoic renal tumors, we recommend intraoperative pathological examination when CT findings do not correspond with the results of ultrasonography.     

Angiomyolipoma in the renal pelvis

A 54-year-old male presented with massive hematuria with bladder tamponade. Computed tomography and magnetic resonance imaging showed a 7.5 x 6.5 x 4.5 cm. mass centered in the left renal pelvis, which is composed of macroscopic fat and soft-tissue component. Differential diagnosis included liposarcoma, lipoma and angiomyolipoma. Urothelial carcinoma was also undeniable because urine cytology was equivocal. Subsequently, a left nephroureterectomy was performed. Pathological examinations revealed a renal angiomyolipoma protruding into the renal pelvis. We present a rare case of angiomyolipoma in the renal pelvis and review the literature concerning these unusual findings of this common neoplasm.     

Renal angiomyolipoma with malignant transformation, simultaneous occurrence with malignity and other complex clinical situations

Renal angiomyolipoma is a benign kidney tumor, which is characterized by the presence of mature or immature fat tissue, thick-walled blood vessels, and smooth muscles. However, there is a rare possibility of transformation to a malignancy. This transformation could be toward sarcoma. And also angiomyolipoma could be associated with renal adenocarcinoma in the same kidney. The aim of this study is to show the association of angiomyolipoma with complex clinical situations such as malign transformation, simultaneous occurrence with adenocarcinoma, bilateral tumors with tuberous sclerosis or Wunderlich Syndrome. Findings of clinical presentation, pathological evaluation, urography, ultrasonography, and computerized tomography of 19 patients who were diagnosed angiomyolipoma in our clinic during 1994–2003 were examined retrospectively. Our records indicated that radical nephrectomy was performed in three cases of angiomyolipoma in which the differential diagnosis from adenocarcinoma could not be made and in another case of angiomyolipoma, which was associated with adenocarcinoma. Simple nephrectomy was performed in four symptomatic angiomyolipoma cases with tumor size larger than 4 cm and partial nephrectomy in another case. In one case, renal angiomyolipoma was associated with adenocarcinoma in the same kidney. In one case, post-operative recurrence of angiomyolipoma developed 7 months after nephrectomy. This patient was diagnosed low-grade leiomyosarcoma. Angiomyolipoma is regarded as a benign tumor of the kidney; however, it may also show aggressive behaviors and rarely transform to sarcoma. It may also exist in the same kidney along with adenocarcinoma or sarcoma.     

乏脂肪肾血管平滑肌脂肪瘤的CT特征分析（附40例报告）

目的通过分析40例术前诊断为肾癌的乏脂肪肾血管平滑肌脂肪瘤的CT影像学特征,以期提高肾脏肿瘤的诊断准确率,减少过度治疗。方法回顾性分析40例术前影像学诊断为肾癌的乏脂肪血管平滑肌脂肪瘤,评价CT平扫及增强后三期扫描中肿瘤的大小、位置、强化模式、强化程度、是否伴有钙化等。结果肿瘤最大径1.6～7.9（3.48±1.68）cm;38例表现为实性占位,2例表现为囊实性占位（BosniakⅣ型）;1例肿瘤伴有钙化;就强化程度而言,13例表现为轻度强化,18例表现为中度强化,9例表现为明显强化;就强化模式而言,28例表现为延迟强化,12例表现为非延迟强化;10例表现为不均匀强化,30例表现为均匀强化。结论 CT强化程度,强化模式及特殊征象在乏脂肪肾血管平滑肌脂肪瘤的诊断中具有一定价值。     

Computed tomographic findings in renal angiomyolipoma: an histologic correlation

Accurate preoperative diagnosis of renal angiomyolipomas is essential if conservative resection or angiographic embolization is to be used. Computed tomographic (CT) scanning failed to diagnose angiomyolipoma preoperatively in 2 patients, and this led to a retrospective review of 6 patients to define the limits of CT scanning in preoperative diagnosis. The CT findings were correlated with the histology of the tumors. Two tumors with positive attenuation coefficients suggestive of renal adenocarcinoma had significant amounts of immature "fetal" fat, and one of these had a virtual absence of mature fat. The relative inability of CT scanning to identify immature "fetal" fat, especially in the presence of abundant vessel and muscle elements, is a limitation to its use in the preoperative diagnosis of angiomyolipoma. A negative attenuation coefficient is highly characteristic of renal angiomyolipoma with mature fat elements. A positive attenuation coefficient, although suggestive of renal cell carcinoma, may be found in angiomyolipomas with paucity of mature fat or high proportions of immature fat.     

转移性恶性肾血管平滑肌脂肪瘤三例报告

目的 探讨转移性恶性肾血管平滑肌脂肪瘤(AML)的诊断和治疗. 方法转移性恶性AML患者3例.男1例,女2例.年龄分别为36、55和37岁.主诉为持续性患侧腰痛1～6个月.2例B超、CT检查发现患肾实性占位.1例B超见肾肿块内不均匀高回声光团,CT测得脂肪负值信号.2例行根治性肾切除术,1例行肾切除术.3例均未放化疗. 结果 肿块切面灰红、灰黄,质软.病理镜下观察:2例瘤细胞呈上皮样,核有异型,伴坏死;1例大多区域为梭形平滑肌,脂肪细胞和血管混杂生长,部分区域细胞呈上皮样.免疫组化结果 均为VM(+),HMIM5(+),Melan-A(+),S-100(-),CK(-).3例病理诊断均为恶性肾AML,2例为上皮样型,1例为经典型、部分上皮样型.1例术后7年出现肺转移,行肺叶切除加清扫,随访12年无瘤生存.1例术后6年复发,行肿块切除术;术后lO年发现肝、后腹膜转移,再行肿块部分切除,随访12年带瘤生存.1例术后4个月出现肝、后腹膜转移,行肿块部分切除,3个月后失访. 结论 恶性肾AML罕见,诊断依靠病理和免疫组化检查.治疗方法无特殊.     

A case of renal angiomyolipoma with marked cystic degeneration and pseudoaneurysm

A 59-year-old woman consulted our hospital for a left renal mass which she had been aware of for 4 years. The tumor was in the lower portion of the left kidney. It was a cystic tumor whose wall was enhanced on computed tomography and magnetic resonance imaging. The lesion 3.0 cm in diameter, which was enhanced equally to the aorta, was found in a part of the wall. It was thought to be a pseudoaneurysm by renal angiography. We suspected a cystic renal cell carcinoma because of the plural feeding arteries and tumor staining, and performed left total nephrectomy. Pathological diagnosis was angiomyolipoma with few fat components. To our knowledge only 3 previous cases of renal angiomyolipoma with marked cystic degeneration have been reported in Japan. In all 3 cases, it was difficult in preoperative diagnosis to distinguish angiomyolipoma with cystic degeneration from cystic renal cell carcinoma complicated cyst. Moreover, this is the first reported case of renal angiomyolipoma with marked cystic degeneration and pseudoaneurysm.     

RENAL ANGIOMYOLIPOMA IN CHILDREN: DIAGNOSTIC DIFFICULTY IN 3 PATIENTS

Purpose

Because angiomyolipoma is less common in children than in adults, its diagnosis can be difficult. We present 3 cases of pediatric angiomyolipoma in which diagnostic problems resulted due to the presenting characteristics.

Materials and Methods

We report on 3 children with unilateral renal angiomyolipoma. Computerized tomography (CT) and ultrasonography revealed 3 large renal masses, 20, 7 and 8 cm. in diameter, respectively. A correct diagnosis was not made preoperatively in any case by CT, ultrasound or fine needle biopsy. Wilms tumor was suspected in the first patient who received preoperative chemotherapy. Imaging was inconclusive in the other 2 cases.

Results

All patients underwent surgical exploration and subsequent nephrectomy due to the large size of the tumor. At followup 33, 23 and 13 months postoperatively all children were well without signs of recurrence.

Conclusions

It has been reported that the demonstration of fat on renal ultrasound and CT can diagnose angiomyolipoma in 95% of the cases. Most radiologists rely solely on CT demonstration of lipid density in the renal mass to diagnose angiomyolipoma but the identification at imaging of lipid tissue may be difficult in small tumors. In our cases the fat content of the tumors was less than 10% despite the large size. This low fat content results in misdiagnosis, since fatty tissue is also present in other renal tumors, such as lipoma, liposarcoma, teratoma and Wilms tumors. We recommend conservative surgery when tumor size permits in pediatric patients with angiomyolipoma to avoid chemotherapy.     

A case of renal angiomyolipoma with bone formation

A case of renal angiomyolipoma with bone formation is reported. A 61-year-old woman was admitted to our hospital with one month history of fever. About 15 cm in diameter mass was palpated in her right lower abdomen. Plain abdominal roentgenography, ultrasonography and computed tomography showed marked calcification in the cephalic portion of the right kidney, tumors surrounding right kidney and another tumor in the right lower abdomen. All these tumors and the kidney constituted a big mass continuously, and no fatty component was demonstrated. Total excision of the mass including the kidney was performed. The mass was 30 X 24 X 10 cm in size and 3,240 g in weight. Histologically, the tumor was compatible to renal angiomyolipoma. But, radiopaque shadows which looked like calcification were disclosed to be bones, and fatty tissues were not seen so much. Therefore, the name "benign mesenchymoma" was thought to be more acceptable than angiomyolipoma in this case. Preoperative diagnosis of renal angiomyolipoma is the demonstration of fatty densities in the tumor, and the characteristic extrarenal development should also be taken into consideration. Furthermore, the bone formation of angiomyolipoma, which is very rare might be an important finding to angiomyolipoma.     

肾良性肿瘤和瘤样病变诊治分析(附49例报告)

目的　提高肾良性肿瘤和瘤样病变的诊治水平。　方法　肾良性肿瘤和瘤样病变 4 9例 ,均行B超和CT检查 ,14例行MRI检查 ,分析临床表现、病理和影像学特点。 2 1例术前未能确诊 ,按肾癌行肾切除术 ;2 8例行保留肾单位的肿瘤切除术。　结果　各种病变临床症状无特异性。血管平滑肌脂肪瘤CT和MRI表现含脂肪组织的影像学特点。彩超检测 2例肾动脉瘤和 2例动静脉瘘有特异性表现。其他良性病变无特异性影像学表现。行保肾手术的 2 8例患者随访 1～ 9年无复发 ,肾功能正常。　结论　B超、CT、MRI和彩超等影像学检查对肾良性肿瘤和病变有重要诊断价值。有依据的保留肾单位的肿瘤切除术和术中行冰冻病理检查可减少误诊误治。     

Surgeon-controlled robotic partial nephrectomy for a rare renal epithelioid angiomyolipoma using near-infrared fluorescence imaging using indocyanine green dye: A case report and literature review

Renal epithelioid angiomyolipoma (E-AML) is a rare variant of angiomyolipoma (AML). It is a mesenchymal tumour believed to originate from the perivascular epithelioid cell (PEC). Unlike conventional AML which are benign, E-AML has a rare aggressive behaviour. Conventional AML is typically triphasic containing adipose tissue, smooth muscle and dystrophic vessels in variable proportions, while E-AML are generally composed of plump spindled and polygonal-shaped “epithelioid cells” showing clear or eosinophilic cytoplasm and occasional pleomorphic multinucleated giant cells. E-AML can be misdiagnosed as renal cell carcinoma (RCC) when these “epithelioid cells” show clearing. Only a small number of cases of E-AML have been reported with the standard treatment being radical or partial nephrectomy. We report the first case report of a surgeon-controlled robotic partial nephrectomy using a near-infrared fluorescence imaging using indocyanine green dye on a 25-year-old woman with a T1B (6.6 cm) right renal mass. The final pathology revealed the diagnosis of E-AML. There was no recurrence and metastases after the 6-month follow-up.     

Computed tomography of perirenal and pararenal inflammatory disease complicating renal calculi

The clinicopathologic features of an angiomyolipoma and a renal cell carcinoma occurring in the same patient are reported. A seventy-four-year-old woman was thought clinically and radiographically to have renal cell carcinoma of the left kidney with a metastasis to the right kidney. At surgery, however, she was found to have an angiomyolipoma in the right kidney and a renal cell carcinoma confined to the left kidney, both of which were resected with a good prognosis for survival. Light microscopy of the angiomyolipoma showed the characteristic admixture of adipose tissue, spindle cells, and hyalinized blood vessels. By electron microscopy, the spindle cells had cytoplasmic myofilaments and pinocytotic vesicles, and were surrounded by a basal lamina, consistent with a smooth muscle cell origin. This case is of interest in light of genetic influences in both of these neoplasms, and from the point of view of patient management.