Renal angiomyolipoma with sarcomatous transformation and pulmonary metastases

Angiomyolipoma of the kidney: from simple hamartoma to complex tumour

Angiomyolipoma is the most common mesenchymal tumour of the kidney, even if for a long time it has been viewed as a hamartoma rather than a neoplasm. It belongs to a family of neoplasms, named PEComa, characterised by the constant presence of perivascular epithelioid cells that co-express smooth muscle and melanogenesis markers. Angiomyolipoma can occur in patients with tuberous sclerosis, a hereditary syndrome due to the alteration of TSC1 or TSC2 genes, or sporadically. Angiomyolipoma and its variants are indolent tumours; however, some epithelioid angiomyolipomas/pure epithelioid PEComas are aggressive, and criteria for malignancy have been proposed to identify those cases. Although typical angiomyolipoma is a straightforward diagnosis, pathologists should be aware of the wide morphological spectrum of its variants which could be tricky in routine clinical practice and could require immunohistochemical analysis for resolution. The differential diagnosis may range from an inflammatory process (for instance xanthogranulomatous pyelonephritis) to the most common renal cancers and sarcomas. The immunoexpression of melanogenesis markers (HMB45 and Melan-A) and cathepsin K is extremely helpful in the majority of cases. Recently, a subset of epithelioid angiomyolipoma/pure epithelioid PEComa harbouring TFE3 gene fusions has been described, raising questions about its relationship with the family of perivascular epithelioid cell tumour. The activation of the mTOR pathway due to genetic alterations of tuberous sclerosis complex in TSC1 or TSC2 genes in angiomyolipoma has also been reported as well as the subsequent therapeutic implications.

Late local, peritoneal and systemic recurrence of renal angiomyolipoma: A case report

Renal angiomyolipoma (AML) is a relatively rare tumor that is generally considered as merely benign. However, epithelioid AML (EAML), an uncommon subtype, is associated with potentially malignant behavior. We herein present the case of a 60-year old male patient who had undergone left nephrectomy with left adrenalectomy and lymphadenectomy for a renal tumor 12 years earlier, and presented to our hospital with dull abdominal pain. The histology report after the previous surgery had revealed an AML of the left kidney with a maximal diameter of 17 cm. Imaging studies demonstrated a large tumor of 13 cm in diameter in the area of the resected kidney, as well as hepatic and peritoneal metastases. Computed tomography-guided core needle biopsy of the mass and revision of the histology of the nephrectomy revealed an EAML. Four years after a two-stage resection of the recurrences the patient is in excellent condition and free of disease. From this case report and the literature review on EAML, it appears that correct histological diagnosis of this subtype of renal AML is crucial. Erroneous diagnosis of simple renal AML instead of EAML may lead to insufficient postoperative management. Clinicians should be aware of the malignant potential of EAML and the need for long-term follow-up. As effective surgical and emerging medical treatment options are available, timely detection of recurrent disease may lead to improved outcome.

Renal Angiomyolipoma: Report of three cases with Regional Lymph Node Involvement and/or with Renal Cell Carcinoma

Aims and background

Angiomyolipomas (AMLs) are benign hamartoid tumors which frequently occur in tuberous sclerosis (TS). They may be manifest at different organ sites such as kidneys, lymph nodes, liver and lung and may be associated with renal cell carcinoma (RCC). The nature of multiple organ involvement in AML (metastasis versus multicentric synchronous tumors), the malignant transformation and the relation of AML to RCC have not been sufficiently clarified.

Study design

Three cases of renal AMLs in patients with tuberous sclerosis associated with lymphangioleiomyomatosis of the paraaortic lymph nodes and/or with RCC are reported. The concise clinical history of the patients as well as the findings of histology, immunohistochemistry and quantitative DNA analysis are presented.

Results

The multicentric form of AML and coincidence of renal AML and RCC were observed in 2 patients. AML and RCC were found within the same focus in one of the cases. RCCs were either aneuploid or “near diploid”, whereas one of the multicentric AMLs showed a discordant DNA ploidy pattern, namely aneuploidy in the kidney and diploidy in the lymph nodes.

Conclusions

The presented cases (all of them underwent periaortic lymphadenectomy) suggest that lymph node involvement in renal AML may be more frequent than expected (1-2% of all AMLs) on the basis of the few reported cases. The discordant DNA ploidy (renal versus lymph node lesions) observed in one of the cases with multicentric AML implies synchronous tumor growth at different sites rather than metastatic disease. The intimate coexistance of RCC and AML (RCC revealed by immunohistochemistry within a larger mass of renal AML) may indicate that malignant transformation of an AML should only be accepted, if such a coincidence is unequivocally excluded.

Invasive Renal Angiomyolipoma With Cytologic Atypia

Renal angiomyolipoma (AML) is a benign neoplasm of the kidney arising sporadically in an idiopathic manner, or syndromically as a component of tuberous sclerosis complex. Although the classic AML has no malignant potential, and is the most common mesenchymal tumor of the kidney, variant AML cases with epithelioid morphology have demonstrated aggressive or invasive behavior. Classic AML, on the other hand, can occasionally display focal histology concerning for sarcomatous transformation, but in the absence of invasive features, it is easy to distinguish from a malignancy. In this article, we describe a remarkable case of classic AML that harbored areas histologically mimicking liposarcoma and invaded into the renal vein and extended up to inferior vena cava, thereby presenting a unique diagnostic conundrum. However, the tumor is negative for a CPM gene amplification, arguing against a liposarcomatous transformation. In addition, the patient does not have any sign of recurrence and metastasis clinically after 2 years of follow-up, also favoring a benign diagnosis of this tumor.

Clinical management of tuberous sclerosis complex over the lifetime of a patient

Tuberous sclerosis complex (TSC) is a genetic disorder characterized by nonmalignant tumors (hamartomas) that can occur in various organ systems, including the brain, kidneys, lungs, skin, eyes, and heart. Clinical manifestations of TSC can occur at any age, thereby making the diagnosis difficult. No typical disease presentation is known, and the clinical presentation usually differs between pediatric and adult patients. Furthermore, variable penetrance of the genetic mutation causes a range of disease severity from very mild to severe, and affected individuals can go undetected for years because many of the clinical manifestations of TSC lack specificity. Once a diagnosis is made, TSC management strategies should be tailored to address the symptoms and risks most relevant to the age of the patient. Improved understanding of the genetic basis of TSC and of the central issue of mTOR overactivation has led to use of pharmacotherapies such as the mTOR inhibitors everolimus and sirolimus in the treatment of TSC disease. In Phase II and III studies, everolimus has demonstrated efficacy and safety in the treatment of both brain (subependymal giant cell astrocytoma) and renal (angiomyolipoma) manifestations associated with TSC. It is important to bear in mind that TSC is a lifelong condition, and for those diagnosed as children, a continuum of care will be needed as they transition from pediatric to adult health services. Clearly identifying the likely differences among diagnosis, monitoring, and management of pediatric and adult patients with TSC is an important step in enabling efficiencies to be maximized without compromising the care provided to patients.

PEComa: morphology and genetics of a complex tumor family

Perivascular epithelioid cell tumors, or PEComas, are mesenchymal neoplasms composed of histologically and immunohistochemically distinctive epithelioid or spindle cells, which are immunoreactive for both smooth muscle and melanocytic markers. The cells in PEComas are typically arranged around blood vessels and appear to form the vessel wall, often infiltrating the smooth muscle of small- to medium-sized vessels. Periluminal cells are usually epithelioid and the more peripheral cells are spindle shaped. The cells have small, round to oval nuclei, sometimes with focal nuclear atypia, and clear to eosinophilic cytoplasm, and no counterpart normal cell has been identified. The PEComa "family" now includes angiomyolipoma, pulmonary clear cell "sugar" tumor and lymphangioleiomyomatosis, primary extrapulmonary sugar tumor, clear cell myomelanocytic tumor of the falciform ligament/ligamentum teres, abdominopelvic sarcoma of perivascular epithelioid cells, and other tumors with similar features at various sites that are simply termed PEComa. Some PEComas occur in patients with tuberous sclerosis complex and share the genetic abnormalities. There is a behavioral spectrum from benign to frankly malignant, and histologic criteria have been proposed for assessing malignant potential. The differential diagnosis can include carcinomas, smooth muscle tumors, other clear cell neoplasms, and adipocytic tumors. PEComas constitute a genetically diverse group that includes neoplasms harboring TFE3 gene rearrangements and those with TSC2 mutations, indicating alternative tumorigenic pathways. Recent advances in therapy of malignant PEComas relate to increased knowledge of specific genetic changes and their effects on metabolic pathways that are susceptible to specific interventions. We review PEComas, emphasizing the diagnostic spectrum and recent immunohistochemical and genetic findings.

Fatal malignant metastastic epithelioid angiomyolipoma presenting in a young woman: case report and review of the literature

Epithelioid angiomyolipomas (EAMLs) are rare mesenchymal tumors whose malignant variant is extremely uncommon and highly aggressive. Treatment strategies include chemo radiation, transcatheter arterial embolization and surgical resection, which has remained the mainstay treatment. Targeted therapies including mammalian target of rapamycin (mTOR) inhibitors such as Temsirolimus may offer some hope for progressive malignant EAMLs that are not amenable to other treatment modalities. We report a fatal case in a young female who presented with rapidly progressive metastatic EAML that did not respond to mTOR therapy. The literature has shown reduction in tumor burden with the use of mTOR inhibitors, but unfortunately due to the rarity of malignant EAML, a meaningful approach to treatment remains challenging.

Renal epithelioid angiomyolipoma with a negative premelanosome marker immunoprofile: a case report and review of the literature

Introduction

The rare variant of renal epithelioid/pleomorphic angiomyolipoma has been reported in approximately 120 cases. One of the most important characteristics to differentiate these tumors from other renal cell neoplasms is their typical reactivity to premelanosome antigens. If such a tumor does not stain for HMB-45 or Melan-A, a specific diagnosis of epithelioid pleomorphic angiomyolipoma cannot be made with certainty.

Case presentation

We present here what is, to the best of our knowledge, the first case of epithelioid/pleomorphic angiomyolipoma of the kidney in a 50-year-old Caucasian man with no history of tuberous sclerosis, and with a tumor marker profile negative for several premelanosome antigens. The tumor was composed of sheets of pleomorphic, round to polygonal epithelioid cells with prominent eosinophilic cytoplasm, large nuclei, many multinucleated, and very prominent nucleoli. There were prominent vessels and rare interspersed smooth muscle fibers, but adipocytes were not identified. A tumor marker profile showed tumor cell reactivity for CD68, calponin and focally for CD10. Intervening smooth muscle was reactive with smooth muscle actin. The tumor lacked reactivity for melanin-associated antigens HMB-45 and Melan-A, and for CD31, pan-cytokeratin (AE1/3) and desmin. Electron microscopic examination of tumor cells confirmed the presence of premelanosome-like granules.

Conclusions

Based on the characteristic microscopic appearance of this tumor, and its overall tumor marker profile, we concluded this was a renal epithelioid/pleomorphic angiomyolipoma with a negative premelanosome antigen phenotype.

Epithelioid angiomyolipoma of the kidney: radiological imaging

OBJECTIVES

To review the imaging findings of renal epithelioid angiomyolipomas.

METHODS

Eight patients treated at two institutions were pathologically diagnosed as having epithelioid angiomyolipoma. All of them underwent computed tomography, and four underwent magnetic resonance imaging. The tumor size, existence of fat, heterogeneity, computed tomography attenuation, degree of enhancement, enhancement pattern and magnetic resonance imaging signal intensity were evaluated.

RESULTS

Intratumoral fat was not detected in any of the cases. On unenhanced computed tomography, the intratumoral attenuation was hyperattenuating in six of the seven patients who were examined using this modality. On T2-weighted images, the signal intensity of the solid component, cyst wall or septum was low in three of the four cases. Four of the eight cases were heterogeneous solid-type accompanied by hemorrhage, necrosis or hyalinization. One homogeneous solid-type lesion was large in size and was pathologically accompanied by neither hemorrhage nor necrosis. All three multilocular cystic types were pathologically accompanied by massive hemorrhage in the cystic component. One was accompanied by spontaneous perirenal hematoma.

CONCLUSIONS

The radiological appearance of most epithelioid angiomyolipomas has a tendency to be hyperattenuating on unenhanced computed tomography images, with low intensities on T2-weighted images. They can be heterogeneously solid, homogeneously solid or a multilocular cystic lesion with massive hemorrhage.

Liver angiomyolipomas: a clinical, radiologic, and pathologic analysis of 22 patients from a single center

BACKGROUND

Liver angiomyolipomas (AML) are mesenchymal neoplasms with an uncertain clinical behavior. The spectrum of presentation, imaging and histologic features, and outcomes were analyzed in all patients treated at Memorial Sloan-Kettering Cancer Center.

METHODS

Demographics, disease, pathologic, treatment, and outcome-related variables for consecutive patients were reviewed retrospectively. All imaging studies obtained at presentation were reexamined, categorized, and compared using Fisher and Wilcoxon tests.

RESULTS

Between 1989 and 2010, 238 patients with AML were seen and 22 (9.3%) had liver involvement (exclusive = 17; combined with kidney = 5). The median age was 53 years; 18 were females, and 15 had symptoms. AML was not suspected at initial presentation in any patient. Fat-containing neoplasms on imaging were larger (P = .03), with more heterogeneous enhancement compared with fat-poor neoplasms (P = .001), but none of the imaging/histologic features correlated with outcome. Thirteen patients underwent resection (R0 = 9), 4 were observed, 2 received chemotherapy, 2 embolization, and 1 embolization plus intra-arterial chemotherapy. Two patients treated with R0-resection recurred and 2 treated with chemotherapy progressed, but no patient died of AML-related causes. At a median follow-up of 36 months, 7 patients were free of disease, 13 were alive with disease, 1 died of an unrelated cause, and another was lost to follow-up.

CONCLUSION

AMLs are rare neoplasms with an indolent course in most patients. Subtypes based on fat content are recognized, but clinical behavior does not seem to be different. Recurrence after resection is not associated with disease-related mortality. Resection may be unnecessary in selected asymptomatic patients if the diagnosis can be established definitively.

Tuberous sclerosis complex: neurological, renal and pulmonary manifestations

Tuberous sclerosis complex (TSC) is an important cause of epilepsy and autism, as well as renal and pulmonary disease in adults and children. Affected individuals are subject to hamartomas in various organ systems which result from constitutive activation of the protein kinase mTOR (mammalian target of rapamycin). The clinical course, prognosis and appropriate therapy for TSC patients are often different from that for individuals with epilepsy, renal tumors, or interstitial lung disease, from other causes. Additionally, TSC serves as a model for other conditions in which the mTOR pathways are also up-regulated. This article reviews the molecular pathophysiology and management of neurological, renal and pulmonary manifestations of the disorder. The use of mTOR inhibitors such as rapamycin and everolimus is discussed and recent clinical trials of these drugs in TSC are reviewed.

Perivascular epithelioid cell neoplasm of the colon

A 17-year-old female presented with rectal bleeding from an ulcerated sigmoid mass in 1994. Initial pathological evaluation revealed a rare clear cell neoplasm of the colon, possibly originating from kidneys, adrenals, lung or a gynecologic source as a metastatic lesion. Extensive imaging studies were negative, and over the next 15 years, she remained well with no recurrence. The original resected neoplasm was reviewed and re-classified as a perivascular epithelioid cell neoplasm (PEComa). Although the long-term natural history of PEComas requires definition, increased clinical and pathological awareness should lead to increased recognition of an apparently rare type of colonic neoplasm that likely occurs more often than is currently appreciated.

Angiomyolipoma in the lung detected 15 years after a nephrectomy for renal angiomyolipoma

Angiomyolipoma is generally found in the kidney, but is especially rare in the lung. Nine cases of angiomyolipoma in the lung have been reported previously, and in 3 of these patients it was involved with nephrectomy for renal angiomyolipoma. The origination of the tumor was not completely recognized, but lymphangioleiomyomatosis and angiomyolipoma are known to have a common feature. The pathogenesis of angiomyolipoma in the lung has recently been researched in relation with lymphangioleiomyomatosis. We review these case reports of angiomyolipoma in the lung and discuss the clinical features and the generation of these tumors.

Contrast enhanced ultrasound of renal masses

Contrast enhanced ultrasound (CEUS) has gained clinical importance over the last years for the characterization of hepatic masses. Its role in extrahepatic indications has been investigated repeatedly but has been less comprehensively studied. Currently more than 50% of renal masses are incidentally diagnosed, mostly by B-mode ultrasound. The method of choice for characterization of renal lesions is contrast enhanced computed tomography (CECT). In the case of cystic lesions CECT refers to the Bosniak classification for cystic lesions to assess the risk of malignant behavior. The majority of masses are renal cell carcinoma, but the exact proportion is controversial. Disadvantages of CECT are a significant risk for patients with impaired renal function, allergic reactions and hyperthyroidism due to iodinated contrast agents. Several studies concerning CEUS for the characterization of both solid and cystic renal lesions have been published, but prospective multicenter studies are missing, the presented data being mainly descriptive. The aim of the this manuscript is to review the current literature for CEUS in renal masses, to summarize the available data and focus on possible concepts for studies in the future.

Perivascular epithelioid cell neoplasms: pathology and pathogenesis

This review article summarizes our current understanding of the clinical, pathologic, immunohistochemical, and genetic aspects of perivascular epithelioid cell neoplasms, a rare group of related tumors defined by both morphologic and immunophenotypic criteria.

Renal involvement in tuberous sclerosis complex and von Hippel-Lindau disease: shared disease mechanisms?

Tuberous sclerosis complex and von Hippel-Lindau disease are distinct autosomal dominant tumor suppressor syndromes that can exhibit similar renal phenotypes and seem to share some signaling pathway components. Similarities exist in the current clinical management of, and the newly identified potential therapeutic approaches for, these conditions. This Review summarizes the pathophysiologic and therapeutic overlap between tuberous sclerosis complex and von Hippel-Lindau disease and highlights the results of recent drug trials in these settings.

The use of the Ki-67 marker in the pathological diagnosis of the epithelioid variant of renal angiomyolipoma

OBJECTIVE

Epithelioid angiomyolipoma (EAML) is a rare malignant variant of renal angiomyolipoma (AML). There were 34 cases of EAML reported in 25 studies (including this present study) over the past decade. About 68% were females and 32% males. The mean age was 40.1 years, 53% developed metastatic disease after nephrectomy, and eight patients had TSC. All cases are reported positive when stained with HMB-45 which also labels all classical AML. This study evaluates the use of Ki-67 (proliferation marker) in the pathological diagnosis of EAML and distinction from classical AML.

METHOD

Immunohistochemical reactions for Ki-67 were generated on multiple representative blocks of tissue obtained from two cases of HMB-45 positive EAML and four cases of classic AML and the percentage of positively staining cells estimated.

RESULTS

Both cases of EAML were strongly positive for Ki-67 while all four classic AML were completely negative.

CONCLUSION

The Ki67 is a useful marker in which distinguishes the malignant epithelioid variant of AML from classic AML.

Malignant angiomyolipoma in the liver: a case report with pathological and molecular analysis

Malignant angiomyolipoma (AML) of the liver is rare. We report a case of AML with malignant transformation and metastases. A 30-year-old man had developed giant hepatic masses. Microscopically, the periphery of the tumor showed components of classic hepatic AML, but the central region contained atypical epithelioid components with extremely pleomorphic and hyperchromatic nuclei with frequent mitotic figures. Immunohistochemical analysis revealed that the epithelioid cells were positive for HMB-45 and smooth muscle actin. Furthermore, the atypical epithelioid cells displayed P53 immunoreactivity and mutation at exon 7 for p53. The tumor showed a typical monoclonal pattern but no loss of heterozygosity or microsatellite instability. Markedly atypical epithelioid cells with vascular invasion, distant metastasis, and fatal outcome were interpreted as malignant characteristics of hepatic AML. It is suggested that large tumor size, pleomorphic nuclei with high proliferation activity, and P53 immunoreactivity may predict the existence of malignant transformation of hepatic AML.

Malignant epithelioid angiomyolipoma of the kidney in a patient with tuberous sclerosis: an autopsy case report with p53 gene mutation analysis

We report an autopsy case of malignant epithelioid angiomyolipoma in a 36-year-old male tuberous sclerosis patient. He had been diagnosed to have a bilateral renal tumor 20 years previously. The left kidney had been surgically resected at the age of 34, and the left renal tumor was pathologically diagnosed as classic angiomyolipoma and epithelioid angiomyolipoma. He suddenly died of cardiac arrest, and at autopsy the right kidney weighed 7120 g. The tumor presented with massive necrosis invading the inferior vena cava, but was not hemorrhagic. Microscopic examination revealed tumor cells varying in size with a predominantly solid proliferation pattern and marked atypical large cells with vesicular nuclei and abundant eosinophilic cytoplasm. Mitotic figures were often encountered, and atypical forms were also present. Metastatic lesions were identified in the right lung, liver, diaphragm, and mesentery. Immunohistochemical examination showed epithelioid angiomyolipoma cells that were focally reactive for HMB-45 and showed diffuse positive staining for Melan-A. No mutation was detected in the p53 gene by polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) analysis despite diffuse immunoreactivity for p53. This case was proven to be malignant because of the occurrence of distant metastases, and showed that p53 mutations are not always associated with malignant transformation in epithelioid angiomyolipoma.

PEComas: the past, the present and the future

The perivascular epithelioid cell (PEC) is a cell type constantly present in a group of tumors called PEComas. PEC expresses myogenic and melanocytic markers, such as HMB45 and actin. Recently, recurrent chromosomal alterations have been demonstrated in PEC. At present, PEComa is a widely accepted entity. In the past 10 years, the use of this term has allowed to report and describe numerous cases permitting to start highlighting the biology of this group of lesions. PEComas are related to the genetic alterations of tuberous sclerosis complex (TSC), an autosomal dominant genetic disease due to losses of TSC1 (9q34) or TSC2 (16p13.3) genes which seem to have a role in the regulation of the Rheb/mTOR/p70S6K pathway. There are some open questions about PEComas regarding its histogenesis, the definition of epithelioid angiomyolipoma and the identification of the histological criteria of malignancy. An innovative therapeutic trial using rapamycin is under way for tumors occurring in TSC such as renal angiomyolipoma and lymphangioleiomyomatosis. Its success could provide the rationale for the use of the same drug in other lesions composed of PECs, especially in the malignant ones.

Clinical presentation of epithelioid angiomyolipoma

OBJECTIVE

Epithelioid angiomyolipomas (AML) of the kidney are malignant tumors with aggressive clinical behavior.

METHODS

We reviewed cases of epithelioid AML recently diagnosed at our institution to highlight the spectrum of clinical presentations.

RESULTS

In all cases, renal lesions seen on computed tomography were suspicious for renal cell carcinoma (RCC). Histologically, these tumors can resemble RCC. The diagnosis of epithelioid AML was established by positive staining for melanoma and smooth muscle cell markers, and presence of perivascular epithelioid cells. One patient presented with a renal tumor extending into the inferior vena cava to the level of the hepatic veins. Two patients developed recurrent, metastatic disease following nephrectomy. One patient with tuberous sclerosis and multiple, bilateral AML developed an enhancing renal tumor that did not contain any fat densities. A partial nephrectomy was performed and pathology revealed epithelioid AML adjacent to conventional AML.

CONCLUSIONS

These tumors are distinguished from RCC by positive immunostaining for melanoma markers and smooth muscle cell markers. They resemble conventional RCC on imaging. Epithelioid AML may be locally aggressive and metastasize.

Perivascular epithelioid cell tumor (PEComa) in the genitourinary tract

Perivascular epithelioid cell tumors (PEComas) are mesenchymal tumors composed of histologically, immunohistochemically, ultrastructurally, and genetically distinctive cells. PEComas have been described in different organs and are considered ubiquitous tumors. In this review we discuss recent informations related to PEComas in the genitourinary tract.

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.

PEComa: what do we know so far?

PEComas (tumours showing perivascular epithelioid cell differentiation) are a family of related mesenchymal neoplasms that include angiomyolipoma, lymphangiomyomatosis, clear cell "sugar" tumour of the lung, and a group of rare, morphologically and immunophenotypically similar lesions arising at a variety of visceral and soft tissue sites. These tumours all share a distinctive cell type, the perivascular epithelioid cell or "PEC' (which has no known normal tissue counterpart). PEComas show a marked female predominance and are composed of nests and sheets of usually epithelioid but occasionally spindled cells with clear to granular eosinophilic cytoplasm and a focal association with blood vessel walls. PEComas appear to arise most commonly at visceral (especially gastrointestinal and uterine), retroperitoneal, and abdominopelvic sites, with a subset occurring in somatic soft tissue and skin. Nearly all PEComas show immunoreactivity for both melanocytic (HMB-45 and/or melan-A) and smooth muscle (actin and/or desmin) markers. A subset of PEComas behave in a malignant fashion. This review examines the members of the PEComa family, with an emphasis on lesions arising outside of the kidney, lung and liver, and discusses preliminary evidence for pathological features that might predict malignant behaviour.

Perivascular epithelioid cell tumor (PEComa) with perirenal manifestation

We present the first case report documenting an 8-month post-surgical follow-up of an exceedingly rare perivascular epithelioid cell tumor (PEComa) with a perirenal location. Furthermore, prognostic parameters discussed in the literature are summarized and concise information regarding imaging characteristics on magnetic resonance imaging is provided. In conclusion, our report points toward PEComa as a family of very rare mesenchymal neoplasms that should be included into deliberations concerning the differential diagnosis of perirenal mass lesions.

[Bilateral renal angiomyolipomas with a thrombus in the inferior caval vein. Rare growth pattern of a benign tumor]

Renal angiomyolipomas are mesenchymal tumors that are composed of fat tissue, smooth muscle cells and vessels. These are benign tumors, but in rare cases they show a more aggressive growth pattern with invasion into the venous system but without revealing any signs of malignancy. We report a new case of bilateral renal angiomyolipomas with a caval thrombus in a 36 year old female patient with tuberous sclerosis, and give a brief review of the related literature.

Lack of response of a metastatic renal perivascular epithelial cell tumor (PEComa) to successive courses of DTIC based-therapy and imatinib mesylate

An 11 year-old girl presented with two large abdominal masses in the left flank and epigastrium and left supraclavicular lymphadenopathy. Subsequent investigations led to the diagnosis of metastatic perivascular epithelioid cell tumor (PEComa) arising from the left kidney. Effective treatment for this rare tumor is not yet known. The tumor did not respond to an initial treatment of two cycles of a dacarbazine (DTIC) based regimen. She was placed on a trial of imatinib mesylate based on tumor expression of c-KIT, a tyrosine kinase targeted by this drug. This report highlights the first documented case of the use of imatinib for PEComa. Lack of response and adverse effects of the drug required discontinuation of therapy.

Tubulocystic Carcinoma, Mucinous Tubular and Spindle Cell Carcinoma, and Other Recently Described Rare Renal Tumors

In the past 10 years, several new renal tumors have been identified. Some have been reviewed in this article, and others have been reviewed elsewhere in this issue. Most have been included in the 2004 edition of the WHO classification of tumors of the urinary system and male genital organs. Tubulocystic carcinoma needs to be studied and characterized more fully.

Loss of calponin h1 in renal angiomyolipoma correlates with aggressive clinical behavior

OBJECTIVES

To investigate whether any immunohistochemical differences exist between two types of renal angiomyolipomas (AMLs). Renal AMLs are generally considered to be benign in nature. However, a few of these tumors have been reported to involve other organs.

METHODS

Tissue specimens from 3 cases of clinically aggressive and 9 cases of clinically indolent renal AMLs were examined histologically and immunohistochemically using antibodies against calponin h1 and alpha-smooth muscle actin. Immunostaining was evaluated semiqualitatively as no staining to strong staining.

RESULTS

The tumor cells in the myomatous component of the aggressive type did not show any reaction to the antibody to calponin h1 protein, but they showed strong immunoreactions with the antibody to the alpha-smooth muscle actin antigen. All cases of the nonaggressive AMLs demonstrated strong immunoreactions with both antibodies used.

CONCLUSIONS

Our initial results in a small series of cases suggest a potential molecular difference between the aggressive and nonaggressive type of AMLs. Loss of calponin h1 from the tumor cells of the aggressive type might be related to their pathologically invasive features, and this aggressive type might be categorized into an intermediate type between the benign and malignant types.

Angiomyolipoma of the Kidney

We report 3 recent cases of angiomyolipoma of the kidney. Although generally regarded as a benign neoplasm, angiomyolipoma rarely behaves in an aggressive manner, producing complicated clinical courses leading to metastasis and death. The presence of epithelioid elements within the tumor can result in difficulty differentiating benign from malignant angiomyolipoma and differentiating this tumor from renal adenocarcinoma. The presence of lymph node involvement can cause difficulty in differentiating multicentric disease in lymph nodes from metastasis to lymph nodes. The presence of cytologic abnormalities in the primary tumor can result in difficulty in differentiating atypia in benign angiomyolipoma from malignant sarcomatous transformation of a benign lesion. The 3 cases reported show many of these problems. Criteria for predicting malignancy in epithelioid tumors and sarcomatous transformation are not well recognized because of the rarity of this entity. The typical immunophenotype of all types of angiomyolipoma (cytokeratin-negative and melanomarkers-positive) is very useful in diagnosis but does not help in the differentiation from renal adenocarcinoma at frozen section. We report the empiric use of Ki67 and p53 in these cases as adjuncts to clinical and histologic assessment in predicting behavior. High Ki67 expression was a feature of malignant epithelioid angiomyolipoma. Low levels of p53 expression were seen in the angiomyolipoma with sarcomatous transformation. Benign angiomyolipomas were consistently negative for both Ki67 and p53.

Renal angiomyolipoma with liposarcomatous transformation: A case report and review of the literature

Renal angiomyolipoma is generally benign, although an uncommon subtype (epithelioid angiomyolipoma) may behave more aggressively. Sarcomatous transformation of the disease is exceedingly rare. We report the first case of a high grade round cell liposarcoma arising in a renal angiomyolipoma.

Renal angiomyolipomata

Renal angiomyolipomata can exist as an imaging curiosity or represent a life-threatening condition. There are likely over 10 million people world-wide who have a renal angiomyolipomata and approximately one tenth of these people also have tuberous sclerosis complex. The optimum treatment of angiomyolipomata is focused on sparing renal tissue and has included no intervention, both total and partial nephrectomy, and embolization. As basic science investigation into the biology of angiomyolipomata progresses, there is even hope for successful drug therapy. Because these renal lesions can be associated with other organ system dysfunction, a number of medical specialists become involved in the care of affected patients. The purpose of this article is to update the nephrologist on the molecular understanding of renal angiomyolipomata and for the possibilities of pharmacologic therapy in the future.

Estrogen receptor is significantly associated with the epithelioid variants of renal angiomyolipoma: A clinicopathological and immunohistochemical study of 67 cases

Perivascular epithelioid cells (PEC) in angiomyolipoma (AML) were recently proposed to be its most common progenitor cells. Histologically, triphasic components were present in various proportions, but were overwhelmingly myogenic in epithelioid variants of AML. Despite histological discrimination, the immunophenotypic profiles between triphasic and epithelioid AML have never been compared. The aim of the present study was to clarify the identity of PEC by using immunoreactivity to estrogen receptor (ER), progesterone receptor (PR), bcl-2 and placenta alkaline phosphatase (PLAP), and to use this information to compare triphasic and epithelioid AML. A total of 33 out of 67 cases of renal angiomyolipoma that underwent surgery were reviewed over the period 1998-2003. Two cases were associated with tuberous sclerosis. Ten patients had other malignant tumors, and three patients had a nodal extension. Immunohistochemistry showed that bcl-2 (59.4%), PLAP (46.9%), HMB-45 (100%) was predominantly localized around vessels. The stem cell markers were absolutely negative in all AML types. The estrogen receptors were positive in 14 cases (42.4%) and the progesterone receptors were positive in five cases. Bcl-2 and both female sex hormone receptors were significantly more frequent in the epithelioid variant of AML than in the triphasic type. Perivascular epithelioid cells express bcl-2, ER, PR and PLAP, and ER could be partly associated with myogenic proliferation.

Malignant monotypic epithelioid angiomyolipoma of the retroperitoneum

Monotypic epithelioid angiomyolipoma (EAML) is an uncommon variant of angiomyolipoma, occurring primarily in the kidney and characterized by a predominance of HMB-45-positive epithelioid cells. EAML is generally considered a benign neoplasm, though rare cases exhibiting malignant behavior have been reported. We describe a patient with a primary retroperitoneal monotypic EAML, composed exclusively of atypical epithelioid cells, which metastasized to the liver and the mediastinum. This case represents, to our knowledge, the first description of metastatic disease occurring in an EAML of this particular site.

Recurrent renal epithelioid angiomyolipoma

Renal angiomyolipoma has traditionally been considered a benign tumor. Recently, a variety of epithelioid angiomyolipomas with malignant potential have been described. We report an adrenal recurrence in a patient who had a cellular angiomyolipoma removed 4 years earlier.

Angiomyolipoma of the liver and lung: a case explained by the presence of perivascular epithelioid cells

We report a case of synchronous hepatic and pulmonary angiomyolipoma not associated with tuberous sclerosis or renal angiomyolipoma. The liver tumor contained tortuous vessels, smooth muscle tissue, and fat. It was partially necrotic and made up of pleomorphic epithelioid smooth muscle cells. Positivity for HMB-45 confirmed the diagnosis of angiomyolipoma. Lung biopsy showed multiple abnormal proliferation of smooth muscle cells exhibiting spindle-shaped or epithelioid morphology. The tumor grew around the vessels, and the cells were positive for HMB-45. The occurrence of this case could be explained by a simultaneous proliferation of perivascular epithelioid cells. To the best of our knowledge, this is the first case of hepatic angiomyolipoma associated with multiple pulmonary angiomyolipomas, mimicking hepatic tumor lung metastases on X-ray examination.

Contemporary diagnosis and management of renal angiomyolipoma

PURPOSE

We present a comprehensive resource that summarizes contemporary advances relevant to the clinical management of renal angiomyolipoma.

MATERIALS AND METHODS

A MEDLINE search was done using the key words angiomyolipoma, hemangioma or lipoma and kidney neoplasm, and therapeutic embolization. References from these articles were reviewed to identify additional relevant source material. We identified 13 series published since 1986 comprising 336 patients as well as 24 reports of therapeutic embolization for angiomyolipoma, comprising 76 patients. To our knowledge we report the largest compilation series to date.

RESULTS

Angiomyolipoma is generally benign, although an uncommon subtype (epithelioid angiomyolipoma) may behave more aggressively. Tuberous sclerosis associated angiomyolipoma tends to be larger, multiple and more likely to cause spontaneous hemorrhage than the sporadic entity. Tumors that hemorrhage tend to be larger. Computerized tomography or magnetic resonance is usually sufficient for diagnosis. Biopsy is rarely useful. Primary indications for intervention include symptoms such as pain or bleeding or suspicion of malignancy. Prophylactic intervention is justifiable for large tumors, in females of childbearing age or in patients in whom followup or access to emergency care may be inadequate. Recent advances that have affected management include improved understanding of tuberous sclerosis complex and angiomyolipoma genetics, the identification of molecular markers that facilitate histopathological diagnosis, and the refinement of embolization and partial nephrectomy techniques.

CONCLUSIONS

Although some cases of angiomyolipoma may require complete nephrectomy, most can be managed by conservative nephron sparing approaches. Ongoing research into the molecular biology and clinical behavior of angiomyolipoma may improve our ability to manage these lesions.

Malignant transformation of renal angiomyolipoma: a case report

We report a case of renal angiomyolipoma (AML) with malignant transformation. A 28-year-old woman developed large bilateral renal masses 5 months before admission to our hospital. She was diagnosed with tuberous sclerosis when she was 4 years old. Total nephrectomy of the left kidney was performed, but she died during the operation. Although the focal region of the resected tumor had the appearance of a classic AML, most of the lesion showed a diffuse proliferation of atypical epithelioid cells resembling that in renal cell carcinoma. The epithelioid cells had extremely pleomorphic and hyperchromatic nuclei with frequent mitotic figures, including atypical forms. Immunohistochemical analysis revealed that the atypical epithelioid cells and the typical AML lesions were both positive for HMB-45 but that the former were negative for epithelial and myogenic markers. The smooth muscle cells and thick-walled vessels were focally positive for muscle-specific actins. Furthermore, the atypical epithelioid cells were immunoreactive for p53, whereas the foci of the typical AML were negative. Examination of the microdissected paraffin-embedded tissues revealed p53 mutations in the malignant epithelioid areas in AML but not in the renal parenchyma or typical AML areas. In this case it is proposed that p53 mutation may play an important role in malignant transformation of renal AML.

Epithelioid angiomyolipoma of the ovary: a case report and literature review

Angiomyolipoma (AML) is a benign mesenchymal neoplasm that mainly occurs in the kidney either sporadically or in patients with tuberous sclerosis complex (TSC). Extrarenal AML is uncommon. We describe a 39-year-old female with a history of TSC and bilateral multicentric renal AML who presented with a persistent cystic ovarian mass that fluctuated in size during 2 years of ultrasonographic observation before its removal by salpingo-oophorectomy. The 4.5-cm mass was solid and cystic and tan-yellow. Microscopic examination showed an admixture of epithelioid cells, smooth muscle bundles, large thick-walled blood vessels, and mature adipose tissue. The epithelioid cells had abundant eosinophilic cytoplasm and many had bizarre atypical nuclei including multinucleated forms. Mitoses were rare. Typical smooth muscle cells and the epithelioid cells were strongly immunoreactive for HMB-45. To our knowledge, this represents the first report of an AML arising in the ovary. The differential with other oxyphilic tumors of the ovary is discussed.

Renal angiomyolipoma: further immunophenotypic characterization of an expanding morphologic spectrum

BACKGROUND

Renal angiomyolipoma is a benign tumor histologically characterized by proliferation of spindle cells, epithelioid cells, and adipocytic cells in concert with many thick-walled blood vessels. To add further diagnostic confusion, an epithelioid cell-predominant variant of renal angiomyolipoma has recently been described. HMB-45 immunoreactivity correlates with ultrastructural striated organelles that closely resemble premelanosomes, although no evidence of melanogenesis has been documented in this tumor.

OBJECTIVE

To further characterize the immunophenotypic and ultrastructural profile of renal angiomyolipoma based on phenotypic cell type (epithelioid, spindle, and adipocytic cell).

DESIGN

Formalin-fixed, paraffin-embedded tissues from 27 renal angiomyolipomas and 8 renal cell carcinomas were immunostained with monoclonal antibodies to the melanoma-associated antigens HMB-45, HMB-50, NKI/C3 (CD63), and tyrosinase; the smooth muscle-related antigens calponin and muscle-specific actin (HHF-35); S100; and cytokeratin (CK). All renal angiomyolipomas were also immunostained with a polyclonal antibody to renin. Ultrastructural examination was performed on 9 selected cases.

RESULTS

All renal angiomyolipomas stained positive for HMB-45, HMB-50, NKI/C3, muscle-specific actin (HHF-35), and calponin. Overall, HMB-45, HMB-50, and NKI/C3 preferentially stained the epithelioid cells. Tyrosinase staining was present in 50% of the renal angiomyolipomas with adequate tissue for staining (12 of 24 cases); positive staining and intensity paralleled HMB-45, HMB-50, and NKI/C3. Muscle-specific actin (HHF-35) and calponin preferentially stained the spindle cells. The adipocytic cells stained positive for both melanoma-associated antigens and smooth muscle antigens. Epithelioid cells, spindle cells, and adipocytic cells were CK, S100, and renin negative. Ultrastructural findings paralleled immunohistochemical staining patterns. Premelanosome-like organelles and electron dense granules were more readily detected in the epithelioid cells within the tumor, whereas ultrastructural characteristics of smooth muscle cells were more easily found in the spindle cells. All renal cell carcinomas stained positive for CK, NKI/C3 staining was variable, and all were negative for HMB-45, HMB-50, smooth muscle actin (HHF-35), and calponin.

CONCLUSION

In renal angiomyolipoma, the epithelioid and spindle cells have preferential staining patterns for melanoma-associated antigens versus smooth muscle antigens, respectively. Positivity in renal angiomyolipoma for HMB-50, NKI/C3, and tyrosinase, in addition to HMB-45, provides evidence for the presence of different melanoma-associated gene products. Immunophenotypic overlap of the 3 histologically distinct renal angiomyolipoma cell populations suggests a common cell line, supporting a unitarian concept for renal angiomyolipoma. Ultrastructural characteristics of the 3 renal angiomyolipoma cell phenotypes parallel the immunophenotype, giving further support to a common cell line. Our study lends further credence to the perivascular epithelioid cell concept as proposed by Bonetti and colleagues.