Cystic angiomyolipoma of the kidney: a clinicopathologic description of 11 cases

Mechanistic Target of Rapamycin Kinase is a Common Convergent Pathway to Renal Neoplasia: A Contemporary Review

Mechanistic target of rapamycin kinase (mTOR) is a member of the phosphatidylinositol-3-hydroxide kinase (PI3 K)-related protein kinase family that functions as a central regulator of cell growth, metabolism, proliferation, and survival. The role of the TSC-mTOR signaling pathway in kidney tumors has been implicated in some hamartoma syndromes; however, with the advent and wide utilization of molecular studies, a growing number of kidney tumors have been linked to somatic or germline mutations involving genes that encode for this pathway, including eosinophilic solid and cystic renal cell carcinoma, low-grade oncocytic tumor, eosinophilic vacuolated tumor, renal cell carcinoma with fibromyomatous stroma and angiomyolipoma, among others. Herein, we review the contemporary developments of mTOR pathway-related renal neoplasia, focusing on the clinicopathologic features of the tumor entities.

TSC1 splicing mutation in renal angiomyolipoma with epithelial cysts without fat: A very rare case report and literature review

Renal angiomyolipoma is a benign mesenchymal tumor that can be divided into classical and other subtypes. Angiomyolipoma with epithelial cysts (AMLEC) is an extremely rare non classical subtype. AMLEC without fat component is even rarer. We report a case of AMLEC without fat in a 29-year-old man who was provisionally diagnosed with cystic renal carcinoma by ultrasonography, abdominal enhanced CT and MRI. He had no complaints, or personal or family history of TSC, or other malignancies. Based on imaging findings, robot-assisted laparoscopic nephron-sparing partial nephrectomy through a retroperitoneal approach was performed for the purpose of both diagnosis and treatment. We diagnosed AMLEC after considering the differential diagnosis of other cystic renal neoplasms, such as cystic renal carcinoma, multilocular cystic renal cell neoplasm of low malignant potential, adult cystic nephroma and mixed epithelium and stromal tumor. Meanwhile, the whole-exon sequencing (WES) results showed insert-splicing mutation in the 21st exon and 20th exon of the TSC1 gene. No treatments were performed after the operation and no evidence of recurrence or metastasis at regular follow-up.

TSC2 nonsense mutation in angiomyolipoma with epithelial cysts: a case report and literature review

Background

Angiomyolipoma with epithelial cysts (AMLEC) is an extremely rare subtype of kidney angiomyolipoma that contains epithelial-lined cysts. The most distinctive immunohistochemical feature of AMLEC is its immunoreactivity with melanocytic markers. AMLEC also has a distinct histological structure, which aids in its pathological diagnosis. To date 27 cases of AMLEC have been reported in 11 case series. However, the molecular biology underlying the pathogenesis of AMLEC remains unexplored.

Case report

A 30-year-old female was diagnosed with AMLEC and underwent partial nephrectomy. Histologically, the cross-section of cystic tissue revealed a multilocular appearance, with some cysts containing thrombus-like material, and the wall thickness was approximately 0.2 ~ 0.3 cm. Additionally, the compact subepithelial cellular stroma showed strong and diffuse nuclear labeling for estrogen receptor, progesterone receptor, and CD10, as well as HMB45 and Melan A, which are markers of melanocytic differentiation. Furthermore, using a DNA targeted sequencing panel with next-generation sequencing, we identified a nonsense mutation in TSC Complex Subunit 2 (TSC2) gene, resulting in the formation of a premature termination codon. Moreover, the mutated genes found to be enriched in the PI3K-AKT pathway. The patient in this case had a favorable postoperative follow-up at 3 months.

Conclusion

To the best of our knowledge, this study represents the first analysis of genotype mutations in AMLEC, providing valuable insights for future clinical practice. These findings have significant potential in guiding the understanding and management of AMLEC, paving the way for further research and advancements in the field.

Angiomyolipoma With Epithelial Cysts: A Rare but Distinct Variant of Angiomyolipoma

Renal angiomyolipomas, common benign tumors, can exhibit slow growth in sporadic cases or have aggressive tendencies when linked to genetic conditions like tuberous sclerosis. This case report focuses on the exceptionally rare angiomyolipoma with epithelial cysts (AMLEC) variant, particularly challenging to diagnose due to its scarcity. Describing a 41-year-old woman's case, initially suspected to be renal cell carcinoma during an infertility evaluation, subsequent partial nephrectomy revealed a tumor comprising smooth muscle, blood vessels, and fat, with cystic regions featuring cuboidal linings and a layer devoid of abnormal cell activity. Immunohistochemistry confirmed specific markers within different tumor components, highlighting the diagnostic complexities of AMLEC and emphasizing the crucial role of histopathological examinations in accurate characterizations.

Tuberous Sclerosis Complex Kidney Lesion Pathogenesis: A Developmental Perspective

The phenotypic diversity of tuberous sclerosis complex (TSC) kidney pathology is enigmatic. Despite a well-established monogenic etiology, an incomplete understanding of lesion pathogenesis persists. In this review, we explore the question: How do TSC kidney lesions arise? We appraise literature findings in the context of mutational timing and cell-of-origin. Through a developmental lens, we integrate the critical results from clinical studies, human specimens, and genetic animal models. We also review novel insights gleaned from emerging organoid and single-cell sequencing technologies. We present a new model of pathogenesis which posits a phenotypic continuum, whereby lesions arise by mutagenesis during development from variably timed second-hit events. This model can serve as a conceptual framework for testing hypotheses of TSC lesion pathogenesis, both in the kidney and in other affected tissues.

Angiomyolipoma with epithelial cysts, an unexpected discovery in a gunshot abdomen: a single case report

Background

Angiomyolipoma with epithelial cysts is a rare variant of an angiomyolipoma that typically occurs sporadically. Patients with pre-existing kidney lesion or disease have significantly increased risk of morbidity and mortality associated with trauma. Abnormal and diseased kidneys are frequently injured by low or insignificant velocity impacts. The vulnerability of these kidneys is related to the type of pathology. However, cystic or hydronephrotic kidneys are more susceptible to trauma. Recent studies have shown an association of this rare entity with tuberous sclerosis complex. Despite the rarity of genetic association of Angiomyolipoma with epithelial cysts and tuberous sclerosis, the emerging findings raise the necessity of genetic testing of these lesions to confirm a remote possibility of tuberous sclerosis complex.

Case presentation

We report a case of a 38-year-old male patient who sustained a right renal injury as a result of a gunshot to the abdomen and underwent an emergency nephrectomy due to hemodynamic instability. A grossly looking shattered kidney was surgically removed. The morphology in conjunction with immunohistochemistry of the specimen favoured a diagnosis of Angiomyolipoma with epithelial cysts.

Conclusion

This is the first reported case of angiomyolipoma with epithelial cysts diagnosed on a nephrectomy specimen from renal trauma. We aim to highlight an approach to renal trauma on a kidney with pre-existing AMLEC as well as an approach to adult cystic renal neoplasms and to propose the importance of genetic testing for Tuberous Sclerosis.

Angiomyolipoma of the kidney-Clinicopathological analysis of 52 cases

The renal angiomyolipoma (AML) is a benign tumor characteristically composed of fat, smooth muscle tissue, and vessels. We collected AMLs from our nephrectomy database, reclassified them according to their histological appearance, recorded the demographic, clinical, and pathological parameters, and compared them with oncocytoma (RO) and renal cell carcinoma (RCC). Immunohistochemistry was ordered in 41 cases. In 2224 nephrectomies, we found 52 AMLs with a 53 mm median size. The mean age was 52.76. Forty-eight tumors were sporadic, while four were hereditary. The revision resulted in 31 classic, 13 leiomyoma-like, five lipoma-like, two epithelioid, and one AML with epithelial cysts. SMA was diffusely positive, except for the epithelioid type, while MelanA harbored stronger expression than HMB45. AML was more frequent in females and appeared ten and 7 years earlier than RO and RCC, respectively. The follow-up time was 7.42 years, and neither tumor-related death nor relapse occurred. AML is rare in nephrectomies and develops primarily in females in their 50s with an average size of 50-60 mm at the surgery. The histological appearance in order of frequency is classic, leiomyoma-like, lipoma-like, epithelioid, and cystic. The MelanA, HMB45, and SMA immunohistochemistry can support the light-microscopic findings.

Cutaneous Angiomyolipoma-A Distinct Entity That Should Be Separated From Classic Angiomyolipoma: Complete Review of Existing Cases and Defining Fundamental Features

Cutaneous angiomyolipoma is a rare mesenchymal tumor that is demographically, clinically, and immunohistochemically distinct from its renal and extrarenal counterparts. We present a case of cutaneous angiomyolipoma in the right retroauricular area of a 35-year-old male patient and provide a broad systematic review of the literature and the largest compilation of cutaneous angiomyolipomas reported to date. According to the findings presented in this review, we conclude that cutaneous angiomyolipoma should be completely separated from renal and extrarenal angiomyolipomas and therefore be considered a distinct entity in the classification of skin tumors.

Renal Epithelioid Angiomyolipoma with Epithelial Cysts Mimicking Cystic Renal Cell Carcinoma: A Case Report of Combination of Two Rare Entities

Renal angiomyolipomas (AMLs) are typically solid tumors, but there have been few reports of a rare cystic variant of AML. AML with epithelial cysts, where the epithelial cyst has a cuboidal epithelial lining, account for the majority of them. Next, epithelioid AML (EAML) with cystic changes due to hemorrhage and necrosis, which is composed of epithelioid cells with abundant eosinophilic cytoplasm, have also been reported. These rare cystic types of AML can be mistaken for other cystic tumors, such as cystic renal cell carcinoma, in preoperative imaging. We report the imaging findings of a rare case of EAML with epithelial cysts.

Renal angiomyolipoma with epithelial cyst

Angiomyolipoma with epithelial cysts (AMLEC) is a recently described entity and is an uncommon subtype of kidney angiomyolipomas. AMLEC is a benign entity but usually masquerades a renal cell carcinoma on imaging examination. AMLEC has a distinct histological and immunohistochemical staining pattern, which helps in the pathological diagnosis. We present a rare case of AMLEC in a 26-year-old female, which was provisionally diagnosed as renal cell carcinoma on radiology. We also summarize the differential diagnosis of this rare variant, its characteristic features, and a review of the literature.

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.

Concurrent Eosinophilic Solid and Cystic Renal Cell Carcinoma and Angiomyolipoma With Epithelial Cysts in the Setting of Tuberous Sclerosis Complex: A Rare Synchronous Occurrence of 2 Distinct Entities

Eosinophilic solid and cystic renal cell carcinoma (ESCRCC) is a recently described distinct renal neoplasm known to occur almost exclusively in female patients with or without tuberous sclerosis complex (TSC). We report a case of ESCRCC with 2 synchronous angiomyolipomas, including 1 angiomyolipoma with epithelial cysts (AMLEC), a rare cystic variant of AML that typically arises sporadically in the absence of TSC, in a 46-year-old woman with TSC. Besides additional copy number alterations identified in ESCRCC via molecular karyotyping, we also report a unique histologic feature of TSC-associated ESCRCC previously not described in detail, with formation of semicircular multinucleated neoplastic giant cells engulfing an additional intact neoplastic cell, simulating emperipolesis. To the best of our knowledge, this is the first reported case of ESCRCC with concurrent AMLEC in a patient with TSC, confirmed through additional genetic testing showing a germline heterozygous mutation in TSC1. Awareness of ESCRCC helps avoid the pitfall of a diagnosis of unclassified renal cell carcinoma, a typically much more aggressive tumor.

Mesenchymal Neoplasms of the Genitourinary System: A Selected Review with Recent Advances in Clinical, Diagnostic, and Molecular Findings

Mesenchymal neoplasms of the genitourinary (GU) tract often pose considerable diagnostic challenges due to their wide morphologic spectrum, relative rarity, and unexpected incidence at GU sites. Soft tissue tumors arise throughout the GU tract, whether from adventitia surrounding or connective tissues within the kidneys, urinary bladder, and male and female genital organs. This selected article focuses on a subset of these lesions, ranging from benign to malignant and encompassing a range of patterns of mesenchymal differentiation, where recent scholarship has lent greater insight into their clinical, molecular, or diagnostic features.

Angiomyolipoma of the Kidneys: Current Perspectives and Challenges in Diagnostic Imaging and Image-Guided Therapy

Angiomyolipomas (AML) are benign tumors of the kidneys frequently encountered in radiologic practice in large tertiary centers. In comparison to renal cell carcinomas (RCC), AML are seldom treated unless they are large, undergo malignant transformation or develop complications like acute hemorrhage. The common garden triphasic (classic) AML is an easy diagnosis, however, some variants lack macroscopic fat in which case the radiologic differentiation from RCC becomes challenging. Several imaging features, both qualitative and quantitative, have been described in differentiating the 2 entities. Although minimal fat AML is not entirely a radiologic diagnosis, the suspicion raised on imaging necessitates sampling and potentially avoids an unwanted surgery. Recently a new variant, epitheloid AML has been described which often has atypical imaging features and is at a higher risk for malignant transformation. Apart from the diagnosis, the radiologist also needs to convey information regarding nephrometric scores which help in surgical decision-making. Recently, more and more AMLs are managed with selective arterial embolization and percutaneous ablation, both of which are associated with less morbidity when compared to surgery. The purpose of this article is to review the imaging and pathologic features of classic AML as well as the differentiation of minimal fat AML from RCC. In addition, an overview of nephrometric scoring and image-guided interventions is also provided.

Evidence of renal angiomyolipoma neoplastic stem cells arising from renal epithelial cells

Renal angiomyolipomas (AML) contain an admixture of clonal tumour cells with features of several different mesenchymal lineages, implying the existence of an unidentified AML neoplastic stem cell. Biallelic inactivation of TSC2 or TSC1 is believed to represent the driving event in these tumours. Here we show that TSC2 knockdown transforms senescence-resistant cultured mouse and human renal epithelial cells into neoplastic stem cells that serially propagate renal AML-like tumours in mice. mTOR inhibitory therapy of mouse AML allografts mimics the clinical responses of human renal AMLs. Deletion of Tsc1 in mouse renal epithelia causes differentiation in vivo into cells expressing characteristic AML markers. Human renal AML and a renal AML cell line express proximal tubule markers. We describe the first mouse models of renal AML and provide evidence that these mesenchymal tumours originate from renal proximal tubule epithelial cells, uncovering an unexpected pathological differentiation plasticity of the proximal tubule.

Renal angiomyolipomas (AML) contain a mix of clonal tumour cells. Here, through reverse tumour engineering experiments, mouse genetics and analyses of human AML tumours, the authors provide evidence that these mesenchymal tumours originate from renal proximal tubule epithelial cells.

Angiomyolipoma with Epithelial Cysts Masquerading as a Cystic Renal Cell Carcinoma

Angiomyolipoma with epithelial cysts (AMLEC) is a very uncommon renal tumor. AMLEC has a characteristic histological appearance and immunohistochemical staining pattern, knowledge of which should preclude misdiagnosis by pathologists. We present a rare case of an AMLEC which was suspected to be a cystic renal cell carcinoma radiologically. We describe the characteristic immunological staining pattern and ultrastructural features of this lesion and discuss the potential differential diagnoses.

Angiomyolipoma With Epithelial Cysts

Angiomyolipoma with epithelial cysts is a rare mesenchymal tumor of the kidney that enters in the differential diagnosis of adult cystic renal neoplasms. These tumors demonstrate a slight female predominance and can present either incidentally or with symptoms, commonly flank pain and hematuria. Unlike conventional angiomyolipoma, this variant is characterized grossly by both solid and cystic areas, and histologically by the presence of single or multiple cysts lined by epithelial cells, a subepithelial "cambium-like" layer of small stromal cells with a prominent capillary vasculature, and a thick exterior wall composed of poorly formed fascicles of smooth muscle and thick-walled dysplastic blood vessels. Tumors show a distinct immunohistochemical profile and are often reactive for melanocytic markers (HMB-45 and Melan-A), as well as estrogen receptor and progesterone receptor. These tumors have an indolent clinical course, with no reports of progression or metastasis in reported cases thus far.

Diagnosis of Renal Angiomyolipomas: Classic, Fat-Poor, and Epithelioid Types

With the increasing discovery of small renal masses with cross-sectional imaging, there has been the concomitant rise in their treatment. With the intent of early curative surgery for a presumed renal cell carcinoma, many renal masses are being resected at surgery without a confirmed diagnosis. Many of them are benign, and some are angiomyolipomas. The diagnosis of renal angiomyolipoma using imaging is, therefore, is as important as ever. Although most, if not all angiomyolipomas with abundant fat are diagnosed readily, some have too little fat to be detected with imaging. This article reviews the current classification, imaging pitfalls, and diagnosis of angiomyolipoma with an emphasis on the fat-poor types. Proper imaging technique, a thorough search for fat, and the appropriate use of percutanoeus biopsy are all needed to eliminate the unnecessary treatment of these benign neoplasms.

A Review of the Literature on Extrarenal Retroperitoneal Angiomyolipoma

BACKGROUND

Extrarenal retroperitoneal angiomyolipomas are rare.

AIM

To review the literature.

RESULTS

Angiomyolipomas, previously classified as hamartomas, are now classified as benign tumours. Thirty cases of primary retroperitoneal angiomyolipomas have been reported. Diagnosis of the disease upon is based radiological and pathological findings of triphasic features of (a) fat and (b) blood vessels and myoid tissue. Immunohistochemistry tends to be positive for HMB45, MART1, HHF35, calponin, NKI-C3, and CD117. The lesion is common in women. Treatment options have included the following: (a) radical surgical excision of the lesion with renal sparing surgery or radical nephrectomy in cases where malignant tumours could not be excluded and (b) selective embolization of the lesion alone or prior to surgical excision. One case of retroperitoneal angiomyolipoma was reported in a patient 15 years after undergoing radical nephrectomy for angiomyolipoma of kidney and two cases of distant metastases of angiomyolipoma have been reported following radical resection of the tumour.

CONCLUSIONS

With the report of two cases of metastases ensuing surgical resection of the primary lesions there is need for academic pathologists to debate and review angiomyolipomas to decide whether to reclassify angiomyolipomas as slow-growing malignant tumours or whether the reported cases of metastases were de novo tumours or metastatic lesions.

Updates in Benign Lesions of the Genitourinary Tract

The genitourinary tract is a common site for new cancer diagnosis, particularly for men. Therefore, cancer-containing specimens are very common in surgical pathology practice. However, many benign neoplasms and nonneoplastic, reactive, and inflammatory processes in the genitourinary tract may mimic or cause differential diagnostic challenges with malignancies. Emerging clinicopathologic, immunohistochemical, and molecular characteristics have shed light on the pathogenesis and differential diagnosis of these lesions. This review addresses differential diagnostic challenges related to benign genitourinary tract lesions in the kidney, urinary bladder, prostate, and testis, with emphasis on recent advances in knowledge and areas most common in diagnostic practice.

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.

Cystic Angiomyolipoma Mimicking Cystic Renal Cell Carcinoma on Computed Tomography Image

We report on a 44-year-old male patient with cystic angiomyolipoma (AML) simulating cystic renal cell carcinoma on computed tomography (CT). The CT scan showed a 2.8-cm left renal cystic mass with an enhancing solid component. No fat density was identified in the mass. These findings were indicative of a cystic renal cell carcinoma. Robot-assisted laparoscopic partial nephrectomy was performed, but the final histologic result was a cystic AML. Herein, we would review the preoperative CT findings, which could have suggested cystic AML.

Renal angiomyolipoma: a radiological classification and update on recent developments in diagnosis and management

Angiomyolipoma is the most common benign solid renal neoplasm observed in clinical practice. Once thought to be a hamartoma and almost always diagnosed by the imaged-based detection of fat, angiomyolipomas are now known to consist of a heterogeneous group of neoplasms. Although all are considered perivascular epithelioid cell tumors, many display different pathology, imaging features, and clinical behavior. The importance of understanding this group of neoplasms is emphasized by the fact that many types of angiomyolipoma contain little to no fat, and despite being benign, sometimes escape a pre-operative diagnosis. These types of angiomyolipomas can all be considered when encountering a renal mass that is both hyperattenuating relative to renal parenchyma on unenhanced CT and T2-hypointense, features that reflect their predominant smooth muscle component. We review recent developments and provide a radiological classification of angiomyolipomas that helps physicians understand the various types and learn how to both diagnose and manage them.

Renal angiomyolipoma: a radiological classification and update on recent developments in diagnosis and management

Angiomyolipoma is the most common benign solid renal neoplasm observed in clinical practice. Once thought to be a hamartoma and almost always diagnosed by the imaged-based detection of fat, angiomyolipomas are now known to consist of a heterogeneous group of neoplasms. Although all are considered perivascular epithelioid cell tumors, many display different pathology, imaging features, and clinical behavior. The importance of understanding this group of neoplasms is emphasized by the fact that many types of angiomyolipoma contain little to no fat, and despite being benign, sometimes escape a pre-operative diagnosis. These types of angiomyolipomas can all be considered when encountering a renal mass that is both hyperattenuating relative to renal parenchyma on unenhanced CT and T2-hypointense, features that reflect their predominant smooth muscle component. We review recent developments and provide a radiological classification of angiomyolipomas that helps physicians understand the various types and learn how to both diagnose and manage them.

A Tubercus Sclerosis Case Accompanied by Cystic Angiomyolipoma and Chronic Kidney Disease Diagnosed during Treatment for Acute Cerebral Infarction

<p>Symptoms of tuberous scelrosis (TS) are mainly related with brain and kidneys. Seizure, mental retardation, other behavioral problems are dominant. A spectrum of renal tumors from benign angiomyolipoma (AML) to polycystic kidney disease, and rarely malignant renal cell carcinoma have been observed. Cystic AML is a rare phenotype of AML. No case of TS with renal cystic AML has been reported in Korea yet. And chronic kidney disease (CKD) in TS has been seldom reported. We experienced a TS case accompanied by renal cystic AML and CKD diagnosed in a 48-year-old female patient who was hospitalized for left side weakness and seizure under the diagnosis of acute cerebral infarction.</p>

Hereditary syndromes with associated renal neoplasia: a practical guide to histologic recognition in renal tumor resection specimens

Many hereditary tumor syndromes are associated with neoplasms of the kidney. It is becoming increasingly well recognized that a given familial tumor syndrome may be very heterogenous in clinical appearance and that unrecognized patients may present initially for the treatment of a renal mass. It is therefore important for surgical pathologists to be aware of the specific gross and microscopic findings in the kidney that suggest a possible syndromic association. In this review, we detail the histologic features of syndromic-associated renal neoplasms, describe the presence of characteristic changes in the background renal parenchyma, and provide an update on associated extrarenal manifestations for each of the following syndromes: von Hippel-Lindau disease, hereditary papillary renal cell carcinoma (RCC), hereditary leiomyomatosis-RCC, Birt-Hogg-Dubé syndrome, tuberous sclerosis complex, germline succinate dehydrogenase mutation, hereditary nonpolyposis colorectal cancer syndrome, hyperparathyroidism-jaw tumor syndrome, PTEN hamartoma syndrome, constitutional chromosome 3 translocation, and familial nonsyndromic clear cell RCC. We also include a synopsis of renal medullary carcinoma because of its association with hereditary hemoglobinopathies.

Angiomyolipoma of the kidney: clinicopathological and immunohistochemical study

OVERVIEW

Although angiomyolipoma (AML) is a relatively rare entity, it is the most common benign mesenchymal neoplasm of the kidney.

THE AIM OF THIS STUDY

To highlight the clinicopathological characteristics of AML and to assess the role of Human Melanoma Black-45 (HMB-45), Melan-A, smooth muscle actin (SMA), S-100 and cytokeratin in its diagnosis.

MATERIALS AND METHODS

The study included 15 cases of AML. Clinical and radiological data were retrieved from the archival files and all cases were subjected to a histopathological evaluation as well as immunohistochemical staining for HMB-45, Melan-A, SMA, S-100, and cytokeratin.

RESULTS

AML was more common in females (female:male = 4:1), the mean age was 53.9 ± 6.45 years. 60% of patients were symptomatic while the remaining 40% were asymptomatic. A statistically significant relationship was found between size of the tumor and the presence of the symptoms (P = 0.02). Patients with tumor size less than 4 cm were asymptomatic, while those with tumor size larger than 4 cm had different symptoms. Thirteen cases were classic AML, while 2 cases were epithelioid AML. Classic AML demonstrated admixture of fatty tissue, thick-walled blood vessels, and smooth muscle, while epithelioid AML was composed mainly of epithelioid cells and contained no fat. HMB-45 was positive in all cases of AML (100%), Melan-A was positive in 13/15 (87%) while SMA was positive in 11/15 (73%) of AML with variable staining intensity. All cases of AML were negative for S-100 and cytokeratin.

CONCLUSION

AMLs have characteristic clinicopathological and immunohistochemical features and their recognition is crucial for proper diagnosis and treatment.

Cystic renal neoplasms and renal neoplasms associated with cystic renal diseases in adults: cross-sectional imaging findings

Cystic renal neoplasms in adults are a heterogeneous group of tumors with characteristic histogenesis, pathological findings, and variable biological profiles. They include disparate entities that are either biologically benign (lymphangioma, cystic nephroma, and mixed epithelial and stromal tumor) or malignant (cystic renal cell carcinoma, multilocular cystic renal cell carcinoma, and primary renal synovial sarcoma). Renal cystic diseases are characterized by cystic changes of the kidneys due to hereditary, developmental, or acquired etiology. Cystic renal diseases such as acquired cystic kidney disease, von Hippel-Lindau disease, and tuberous sclerosis are associated with the development of a wide spectrum of benign and malignant renal neoplasms. Most cystic renal tumors and cystic disease-associated renal neoplasms show characteristic cross-sectional imaging findings that permit accurate diagnosis. In addition, cross-sectional imaging is pivotal in the follow-up and surveillance of adult cystic tumors of the kidney.

Cellular metanephric stromal tumor in a postmenopausal woman: a case report with review of the literature

Metanephric stromal tumor (MST) of the kidney is a rare pediatric neoplasm which has rarely been reported in adults. The authors present a case of MST, cellular type, an unreported variant, in a 56-year-old postmenopausal woman. The 9.0-cm tumor was solid, unencapsulated, and well circumscribed, with a firm homogeneous cut surface. The tumor was purely stromal with dense spindle-cell proliferations displaying prominent schwannoma-like architecture, intratumoral angiodysplasia, and entrapped native renal tubules with "onion-skin" tumor collarettes. The tumor stroma expressed CD34, estrogen, and progesterone and did not express desmin, smooth muscle actin, S-100, or TLE-1. Considering the characteristic morphology and immunophenotype, a diagnosis of "metanephric stromal tumor, cellular type," was made. This is an exceptionally rare disease manifestation in an adult patient and the first description of MST with such high stromal cellularity, making this case unique in both clinical and pathological presentation.

Cathepsin K expression in the spectrum of perivascular epithelioid cell (PEC) lesions of the kidney

The perivascular epithelioid cell (PEC) is a unique cell type coexpressing contractile proteins (mainly α-smooth muscle actin), melanocytic markers, including microphthalmia-associated transcription factor (MITF), and estrogen and progesterone receptors. It is constantly present in a group of tumors called PEComas. Renal PEComas include the common angiomyolipoma as well as less common lesions such as microscopic angiomyolipoma, intraglomerular lesions, angiomyolipoma with epithelial cysts, epithelioid angiomyolipoma, oncocytoma-like angiomyolipoma and lymphangioleiomyomatosis of the renal sinus. It has been demonstrated that most of these lesions are determined by mutations affecting genes of the tuberous sclerosis complex, tuberous sclerosis 1 (TSC1) and tuberous sclerosis 2 (TSC2), with eventual deregulation of the RHEB/MTOR/RPS6KB2 pathway, and it has been observed that some PEComas regressed during sirolimus therapy, an MTOR inhibitor. Recently, overexpression of MITF has been related to the expression of the papain-like cysteine protease cathepsin K in osteoclasts where it has inhibited MTOR. The aim of this study is to evaluate cathepsin K immunohistochemically in the entire spectrum of PEComa lesions in the kidney. The study population consisted of 84 renal PEComa lesions, including 5 composed predominantly of fat (lipoma-like angiomyolipoma), 15 almost exclusively composed of spindle-shaped smooth muscle cells (leiomyoma-like angiomyolipoma) and 31 common angiomyolipomas composed of a mixture of fat, spindle and epithelioid smooth muscle cells, and abnormal thick-walled blood vessels, 15 microscopic angiomyolipomas, 5 intraglomerular lesions, 2 oncocytoma-like angiomyolipomas, 8 epithelioid angiomyolipomas, 2 angiomyolipomas with epithelial cysts and 1 example of lymphangioleiomyomatosis of the renal sinus. In all of the renal PEComas, cathepsin K was found to be constantly and strongly expressed and seems to be a more powerful marker than other commonly used markers for their identification, especially to confirm the diagnosis on needle biopsies.

Angiogenesis and lymphangiogenesis in sporadic hepatic angiomyolipoma

Angiogenesis and lymphangiogenesis are critical processes for tumor growth, invasion, and metastasis. The present study aimed to investigate the distribution and clinical significance of angiogenesis and lymphangiogenesis in hepatic angiomyolipoma (AML). We performed immunohistochemical staining for endothelial cell markers (CD34 and podoplanin) on 80 cases of sporadic hepatic AMLs. Microvessel density (MVD) and lymphatic vessel density (LVD) were determined in intratumoral and peritumoral regions and adjacent non-tumorous liver tissues. All hepatic AMLs showed positive staining for CD34 and podoplanin. Intratumoral and peritumoral MVDs and LVDs were significantly higher than those in adjacent liver tissues (P<0.001). No statistical difference in both MVD and LVD was found between intratumoral and peritumoral areas. Large tumors (>5cm) had a significantly increased MVD and LVD as compared with smaller tumors. A significant positive correlation was found between average LVDs and MVDs (r=0.567, P<0.001), and LVDs were a relatively lower event as compared with MVDs. Double immunostaining revealed that no neoplastic cells positive for HMB-45, an antibody reacting with melanosome-associated antigen, were concurrently immunoreactive for endothelial cell markers. In conclusion, intratumoral and peritumoral angiogenesis and lymphangiogenesis commonly occur in hepatic AMLs, thus representing potential therapeutic targets for this disease.

Distinctive morphology of renal cell carcinomas in tuberous sclerosis

Tuberous sclerosis complex results from mutations in 1 of 2 interacting gene products, hamartin or tuberin. The syndrome is characterized by hamartomas and neoplastic lesions, including angiomyolipomas of the kidney and other organs. Renal cell carcinoma (RCC) in tuberous sclerosis remains relatively poorly characterized because historical studies were confounded by the inclusion of epithelioid angiomyolipomas. The authors present a patient with tuberous sclerosis and bilateral renal lesions, including multiple minute angiomyolipomas, cortical cysts, and 4 separate RCCs of unclassified type. The carcinomas shared distinctive morphological features, including sheet-like, glandular, trabecular, or cystic architecture and abundant granular eosinophilic cytoplasm. By definition, the carcinomas were keratin positive and negative for HMB-45 and Melan-A. Detailed immunohistochemical analysis revealed heterogeneity among the cortical cysts and carcinomas. The histopathological features of these carcinomas illustrate characteristics of renal carcinoma that are probably related to genetic alterations of tuberous sclerosis.

Renal angiomyolipoma: clinicopathologic study of 194 cases with emphasis on the epithelioid histology and tuberous sclerosis association

The majority of renal angiomyolipoma (AML) is sporadic and occasionally it occurs as part of tuberous sclerosis complex (TSC). Epithelioid AML (EAML), an uncommon variant, is considered potentially malignant based on anecdotal case reports. The prognostic significance of epithelioid component in an otherwise typical AML is uncertain. We studied 194 AMLs for the clinicopathologic features of epithelioid and TSC-associated AMLs. Epithelioid component was present in 15 cases (7.7%) with an average amount of 51% (range: 10% to 100%). Histologically, the epithelioid tumor cells were categorized into small, intermediate, and large cell type based on the cell size. Worrisome histologic features were seen in many EAMLs, including coagulative tumor necrosis in 27% (4/15), nuclear atypia in 93% (14/15), mitosis in 47% (7/15), and atypical mitosis in 1 case. All 15 EAML patients had a mean follow-up time of 5.1 years and none had local recurrence or distant metastasis. Sixteen (8.2%) AMLs occurred in patients with definitive TSC. Three histologic features, namely microscopic AML foci, epithelioid component, and epithelial cysts, were present in 10 (62.5%), 4 (25%), and 44% (7/16), respectively, of TSC-associated AMLs, compared with 11 (6.2%), 11 (6.2%), and 6 (3.4%), respectively, in non-TSC-associated AMLs (P value all <0.01). In summary, all 15 cases of EAMLs in our study had benign clinical outcomes despite adverse pathologic features. Epithelioid component, epithelial cysts, and microscopic AML foci are strongly associated with TSC and the presence of all 3 features should raise strong suspicion for TSC.

Retroperitoneal lymphangioleiomyomatosis associated with endosalpingiosis

A case of retroperitoneal lymphangioleiomyomatosis (LAM) arising from endosalpingiosis is described. A 25-year-old woman with no history of tuberous sclerosis or hormonal therapy presented with a painless, palpable abdominal mass. Computed tomographic and magnetic resonance imaging studies of the abdomen demonstrated a 4 cm cystic mass in the retroperitoneum. Macroscopically, the excised retroperitoneal cyst was multilocular and measured 4.0 x 3.5 x 3.5 cm. Histologically, the lesion demonstrated three components. The first comprised multiple cysts or glands lined by columnar epithelial cells with cilia. The second component was a condensation of small stromal cells immediately subjacent to the cystic epithelium or glands. The third component was a thick exterior wall composed of plump spindle cells with clear to palely eosinophilic cytoplasm in a fascicular pattern, and slit-like vascular spaces, resembling LAM. Immunohistochemically, the epithelium and glands were positive for cytokeratin 7. The stromal cells were positive for vimentin and CD10. The cells of the LMA-like component showed positive staining for HMB45, alpha-smooth muscle actin, muscle actin and h-caldesmon. The lesion, LAM arising from endosalpingiosis, represents a distinctive pathologic entity that should be recognized and studied further. This type of lesion should be included in the differential diagnosis of retroperitoneal cystic lesions.

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.

Mixed epithelial and stromal tumour (MEST) of the kidney: report of 14 cases with male and PEComatous variants and proposed histopathogenesis

AIMS

This article adds new cases and variants of MEST with discussion of the histopathogenesis.

METHODS AND RESULTS

Fourteen MEST were originally diagnosed as cystic nephroma which represents an incidence of 1.6% of renal neoplasms in adults. In females, the stromal component showed areas of müllerian differentiation with positive immunoreactivity for oestrogen (ER) and progesterone receptors (PR) and CD10. Immunoreactivity for HMB45 was identified in a single case having a leiomyomatous appearance. The epithelial component displayed features of müllerian epithelium and reactive renal tubular cells. In two male cases, MEST consisted of fibrous and smooth muscle stroma and cysts lined only by reactive renal tubular cells. Immunoreactivity for ER and PR was focal and weak.

CONCLUSIONS

MEST represents a tumour developing from müllerian-like stromal cells in the kidney. The neoplastic stroma encroaches on the renal tubules and has the potential to stimulate the growth of the renal tubules by contact, with development into cysts. Furthermore, the müllerian stroma likely induces the renal tubules to differentiate into müllerian-like epithelium. Melanocytic differentiation of the stroma may occur which represents the PEComatous variant. MESTs in males were histopathologically slightly different from those in females due to the different hormonal milieu.

Angiomyolipoma with epithelial cysts (AMLEC): a rare but distinct variant of angiomyolipoma

Angiomyolipoma with epithelial cysts (AMLEC) is a recently described distinct cystic variant of angiomyolipoma (AML). To date 15 cases of AMLEC have been reported in 2 case series. We report the 16th case in a 39-year-old female. Her left kidney tumor was discovered incidentally. Partial nephrectomy was performed. Histologically, the tumor was composed of three components: 1) epithelial cysts lined by cuboidal to hobnail cells; 2) compact subepithelial mullerian-like AML stroma with admixed chronic inflammation; and 3) muscle-predominant AML with dysmorphic blood vessels exterior to the subepithelial stroma. Immunohistochemically, the subepithelial stroma stained most intensely with HMB-45 and Melan-A, whilst the muscle-predominant AML areas stained most intensely with smooth muscle actin and desmin. Estrogen receptor (ER), progesterone receptor (PR), and CD10 stained most intensely in the subepithelial stroma. The cyst lining was positive for pancytokeratin, but negative for HMB-45, Melan-A, ER, PR, and CD10. The patient is alive with no evidence of disease, 12 months postoperatively, and yearly follow-up CT scans are planned.

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.