Renal pathology in the tuberous sclerosis complex

Epithelioid angiomyolipoma with vascular invasion: An aggressive presentation of an unusual AML variant

Renal angiomyolipoma (AML) is a typically benign renal tumor that is divided into 2 classes, the classical variant and the more aggressive epithelioid variant. It is extremely rare for an AML to exhibit aggressive features such as vascular invasion. We present the case of a 36-year-old female who presented with right lower quadrant pain for 9 months and was found to have an AML with tumor extension into the renal vein and the IVC. Diagnosis was confirmed with histopathology and the patient was treated with a total nephrectomy. The epithelioid subtype of AML is a rare variant that should be considered in the differential of a renal mass with vascular invasion.

Kidney Podocyte Zebra Bodies after Lung Transplantation for Lymphangioleiomyomatosis

A 55-year-old woman showed progressive renal dysfunction after unilateral deceased-donor lung transplantation for lymphangioleiomyomatosis. A kidney biopsy showed a striped pattern of interstitial fibrosis, suggesting calcineurin inhibitor toxicity, and zebra body accumulation was found predominantly in the podocytes, characteristics of Fabry disease. Nevertheless, she had no extra-renal symptoms of the disease, and gene testing identified no known mutation or exon deletion. Our case report and literature review suggest that this atypical lysosomal inclusion may be phospholipidosis induced by sertraline. Potential underlying etiologies linking zebra body deposits may be not only hereditary but also drug-induced phospholipidosis.

Complex Arterial Pathology of Angiomyolipomas of Tuberous Sclerosis

Based on observations at angiography, it was hypothesized that angiomyolipomas (AMLs) associated with tuberous sclerosis complex (TSC) have a more robust parasitic blood supply and require more complex embolization involving lower order vessels compared with the non-TSC patients' AMLs. This was a retrospective review of 71 patients who underwent angiography and embolization for renal AML at multiple centers within a single health system. All of the patients with TSC (11/11) were found to have "complex" tumor vascular supply. Of the patients with sporadic AML, 51/60 (85%) had "simple" tumor vascular supply. Sporadic cases with a complex tumor blood supply were larger tumors, with an average size of 11.5 cm. This study supports our hypothesis that AMLs associated with TSC have more complex tumor vascularity compared with sporadic lesions, and aims to better prepare interventionalists to deal with the complex cases.

Parvalbumin immunohistochemical expression in the spectrum of perivascular epithelioid cell (PEC) lesions of the kidney

Parvalbumin is a cytosolic calcium-binding protein expressed in the distal convoluted tubule of the renal nephron. Among epithelial renal tumors, the reactivity for parvalbumin is observed in chromophobe renal cell carcinomas and frequently in oncocytomas. On the other hand, there are no data available on parvalbumin expression in the mesenchymal tumors of the kidney. Therefore, the purpose of this study was to evaluate the expression of parvalbumin in the spectrum of PEC (perivascular epithelioid cells) lesions of the kidney. Sixty-six PEC lesions (37 classic angiomyolipomas, 10 microscopic angiomyolipomas, 7 epithelioid angiomyolipomas/pure epithelioid PEComas, 5 leiomyoma-like angiomyolipomas, 3 lipoma-like angiomyolipomas, 2 intraglomerular lesions, 1 angiomyolipoma with epithelial cysts (AMLEC), and 1 sclerosing angiomyolipoma) were immunohistochemically stained with parvalbumin. Overall, parvalbumin immunostain was found in fifty-six PEC lesions (85%) and absent in the remaining ten cases (15%). Classic angiomyolipomas were positive in almost all cases (97%). Intraglomerular lesions and AMLEC showed parvalbumin immunolabeling as well. None of the 7 epithelioid angiomyolipomas/pure epithelioid PEComas or the only sclerosing angiomyolipoma expressed parvalbumin. In conclusion, we demonstrated the immunolabeling of parvalbumin in almost all PEC lesions of the kidney, but not in the epithelioid angiomyolipoma/pure epithelioid PEComa. This finding could shed light on some biological characteristics observed in the PEC lesions such as the plasticity of their cellular component. Moreover, parvalbumin may be another useful tool in the differential diagnosis among epithelioid angiomyolipoma/pure epithelioid PEComa with other renal eosinophilic tumors, such as oncocytoma and chromophobe renal cell carcinoma.

Renal angiomyolipoma: Clinico-pathologic study of 17 cases with emphasis on the epithelioid histology and p53 gene abnormalities

BACKGROUND

Epithelioid angiomyolipoma (EAML) is a rare potentially malignant variant of renal angiomyolipoma (RAML). This study aims to determine whether RAML clinico-pathologic and molecular features (i.e. p53 gene abnormalities) differ significantly with regards to its histologic variant or to the presence of an epithelioid component within it.

METHODS

Consecutively resected RAML were reviewed, tumours comprising at least 80% of epithelioid cells were considered as EAML according to the 2016 World Health Organization classification of tumours of the kidney. P53 gene abnormalities were investigated using both immunohistochemical and molecular analysis.

RESULTS

A total of 3 EAML among 17 RAML were identified, accounting for 3.9% of the total AML cases. Fatty aspect on imaging was more observed within tumours devoid of an epithelioid component. EAML showed a higher mitotic rate and a stronger p53 staining, no renal poles involvement and was not treated by nephron sparing surgeries. RAML comprising an epithelioid component demonstrated severer nuclear atypia as well as stronger p53 staining. P53 gene sequencing revealed a missense mutation (c.747G > C) in one classic AML harbouring a strong labelling with p53.

CONCLUSIONS

Strong p53 staining in a RAML, even in the absence of gene mutation, may suggest the presence of an epithelioid component or of a truly EAML. To the best of our knowledge, c.747G > C p53 gene mutation is being reported for the first time in a RAML, although its role in AML pathogenesis is still unknown.

Burden of renal angiomyolipomas associated with tuberous sclerosis complex: results of a patient and caregiver survey

Background

Tuberous sclerosis complex (TSC) is a rare genetic disorder characterized by benign tumors in multiple organs, including non-cancerous kidney lesions known as renal angiomyolipomas. This study’s objective is to describe the age-stratified morbidity, treatment patterns, and health-related quality of life of TSC patients with renal angiomyolipomas in the United States. A cross-sectional, anonymous web-based survey was conducted with a convenience sample of TSC patients and caregivers identified through a patient advocacy organization.

Results

Out of the total sample of 676, 182 respondents reported having kidney complications with 33% of the pediatric group and 25% of the adult group with TSC reporting them. Of those with kidney complications, 110 (60%) reported a diagnosis of renal angiomyolipomas, of which 79 (72%) were adult patients and 31 (28%) were pediatric age patients. Eighty-four percent of the pediatric group and 76% of the adult group reported lesions on both kidneys. Of the patients experiencing involvement of only one kidney, 60% of the pediatric group and 21% of the adult group reported having multiple tumors within the affected kidney. Almost all of the sample (99%) reported seeing a physician and having a procedure or test for TSC in the past year. Less than half the respondents (44%) reported being hospitalized in the past year. Thirty-nine percent reported an emergency room visit as well. Compared to scores for patients with kidney disease, the angiomyolipoma adult patients reported significantly lower Mental Component Summary scores on the SF-12.

Conclusions

Renal angiomyolipomas burden leads to frequent healthcare resource use including hospitalization, invasive treatments, and surgical procedures, which result in an impaired mental health related quality of life.

Molecular Characterization and Putative Pathogenic Pathways of Tuberous Sclerosis Complex-Associated Renal Cell Carcinoma

Tuberous sclerosis complex–associated renal cell carcinoma (TSC-RCC) has distinct clinical and histopathologic features and is considered a specific subtype of RCC. The genetic alterations of TSC1 or TSC2 are responsible for the development of TSC. In this study, we assessed the mTOR pathway activation and aimed to evaluate molecular characteristics and pathogenic pathways of TSC-RCC. Two cases of TSC-RCC, one from a 31-year-old female and the other from an 8-year-old male, were assessed. The mTOR pathway activation was determined by immunohistochemistry. The mutational spectrum of both TSC-RCCs was evaluated by whole exome sequencing (WES), and pathogenic pathways were analyzed. Differentially expressed genes were analyzed by NanoString Technologies nCounter platform. The mTOR pathway activation and the germline mutations of TSC2 were identified in both TSC-RCC cases. The WES revealed several cancer gene alterations. In Case 1, genetic alterations of CHD8, CRISPLD1, EPB41L4A, GNA11, NOTCH3, PBRM1, PTPRU, RGS12, SETBP1, SMARCA4, STMN1, and ZNRF3 were identified. In Case 2, genetic alterations of IWS1 and TSC2 were identified. Further, putative pathogenic pathways included chromatin remodeling, G protein–coupled receptor, Notch signaling, Wnt/β-catenin, PP2A and the microtubule dynamics pathway in Case 1, and mRNA processing and the PI3K/AKT/mTOR pathway in Case 2. Additionally, the ALK and CRLF2 mRNA expression was upregulated and CDH1, MAP3K1, RUNX1, SETBP1, and TSC1 mRNA expression was downregulated in both TSC-RCCs. We present mTOR pathway activation and molecular characteristics with pathogenic pathways in TSC-RCCs, which will advance our understanding of the pathogenesis of TSC-RCC.

Giant Perivascular Epithelioid Cell Tumor of the Orbit: A Clinicopathological Analysis and Review of the Literature

Aim

To describe and review the clinical, radiological, and histopathological characteristics of an orbital perivascular epithelioid cell tumor (PEComa).

Methods

A systematic review of clinical records, radiological investigations, microscopic features, and immunohistochemical characteristics was done.

Results

A 9-year-old female child presented with a year-long history of a large orbital mass associated with painless, progressive proptosis of the right eye. Radiologically, a well-defined orbital mass was seen with no intracranial extension. Excision was performed and histopathological examination showed uniform epithelioid cells in nests separated by thin fibrovascular septae. The tumor cells stained positively for Human Melanoma Black-45, but neg-atively for desmin, S-100, smooth muscle actin, MyoD1, microphthalmia-associated transcription factor, vimentin, CD10, CD31, and CD34 with a low proliferation index of 5-7%. Based on the tumor's morphological and immuno-histochemical characteristics, a diagnosis of giant orbital PEComa was made. No recurrence was seen at the last follow-up.

Conclusions

PEComas are uncommon mesenchymal neoplasms that have typical histological features, with an immunohistochemical profile of negativity for epithelial markers and positivity for melanocytic markers. For benign PEComas, complete excision is advised. However, since PEComas elsewhere in the body have been known to be malignant, a close follow-up of such cases is recommended.

Natural history of patients with tuberous sclerosis complex related renal angiomyolipoma

OBJECTIVE

To examine temporal relationships between tuberous sclerosis complex (TSC) and renal angiomyolipoma diagnosis and outcomes, treatment, and healthcare utilization.

METHODS

Administrative data from the MarketScan Commercial Database was used to select TSC-related renal angiomyolipoma patients during 1 January 2000-31 March 2013. Patients were followed until the earliest of inpatient death or end of enrollment or study. Occurrence of kidney-related outcomes, kidney-related procedures, and all-cause healthcare utilization and time to occurrence were reported. Kaplan-Meier curves were used to display the unadjusted distribution of time to outcome.

RESULTS

A total of 605 patients were selected (<18 years N = 225; ≥18 years N = 380). Mean time from TSC to renal angiomyolipoma diagnosis was 25.7 months in younger and 16.9 months in older patients. Patients ≥18 years had higher rates of chronic kidney disease (CKD), hematuria, kidney failure, embolization (EMB), and partial and complete nephrectomy compared to patients <18 years (all p < .05). Mean time from TSC-related renal angiomyolipoma diagnosis to CKD, hematuria, kidney failure, EMB, first emergency room and inpatient visits was shorter in older compared to younger patients (all p < .05). Probability of developing CKD was approximately 0.8 and 0.95 within 3 years in younger and older patients, respectively.

CONCLUSIONS

Patients with TSC-related renal angiomyolipoma had high rates of kidney-related outcomes and procedures. These events sometimes preceded the angiomyolipoma diagnosis. A key study limitation was that due to the small sample size, results may have been biased by outliers. Research is needed to determine whether earlier angiomyolipoma diagnosis can impact occurrence of events and reduce healthcare utilization.

Healthcare utilization and costs in patients with tuberous sclerosiscomplex-related renal angiomyolipoma

OBJECTIVE

To quantify healthcare utilization and costs in patients with tuberous sclerosis complex (TSC) and renal angiomyolipoma (AML) in a matched cohort of patients without TSC or AML.

METHODS

Administrative data from the MarketScan Research Databases were used to select patients with TSC and renal AML during January 1, 2000-March 31, 2013 from the Commercial database and January 1, 2000-June 30, 2012 from the Medicaid database. Patients were required to have at least 30 days of follow-up from initiation into the study, and were followed until inpatient death, end of insurance coverage, or the end of study. Age, calendar year, and payer-matched controls that had no TSC and no AML were selected. All-cause annualized healthcare utilization and costs were calculated by service category.

RESULTS

A total of 218 patients under 18 years and 377 patients 18 years and older with TSC-renal AML were selected from the Commercial database, and matched to 654 and 1,131 controls, respectively. Thirty-eight patients under 18 years and 110 patients 18 years or older with TSC-renal AML were selected from the Medicaid database, and matched to 54 and 212 controls, respectively. Within the Commercial cohort, and across both age groups, TSC-renal AML patients utilized more healthcare services than their matched controls. Within the Medicaid cohort, in both age groups, utilization was higher in TSC-renal AML patients vs control patients for inpatient admissions, emergency room visits, physician office visits, and hospital-based outpatient visits. Across age groups and in both the Commercial and Medicaid cohorts, the annual average total costs were significantly higher in TSC-renal AML patients compared to control patients (p < 0.05 for all). Healthcare costs ranged from $29,240-$48,499 for TSC-renal AML patients and from $2,082-$10,864 for control patients.

CONCLUSIONS

Compared to controls, TSC-renal AML patients incurred substantially higher annual healthcare utilization and costs.

Microsatellite analysis for differentiating the origin of renal angiomyolipoma and involved regional lymph node

Renal angiomyolipoma (AML) with the regional lymph node (LN) involved leads to a question of metastasis versus multicentric origin when their histology are similar. As the genomic instability is a common feature of cancer, we hypothesized that independently arising neoplasms in an individual patient would exhibit measurable genomic variation, facilitating the discrimination of tumor lineage and relatedness. Our study enrolled 12 patients who were diagnosed with nodal-involved renal AML at West China Hospital. Genomic DNA from kidney and lymph node lesion from individuals was analyzed through PCR-based analysis which using six microsatellite markers to identify discordant allelic variation. The results showed all 12 patients underwent surgical treatment and none suffered local recurrence or distant metastasis during the follow-up. Ten patients of the included cases showed a consistent trend that all corresponding to six microsatellite markers were detected in DNA from renal AMLs but were reduced or not observed in DNA from the paired LN. With this technique, a possible lineage relationship cannot be excluded between renal AMLs and LN. Thus when enlarged LN were found in images, active surveillance should be taken into consider; if enlarged LN were found intraoperatively, LN resection might be necessary to demonstrate their pathological nature.

Renal epithelioid angiomyolipoma: Histopathologic review, immunohistochemical evaluation and prognostic significance

Epithelioid angiomyolipoma (EAML) is considered to be a potentially malignant tumor and requires a differential diagnosis from renal cell carcinoma. In this study, we assessed the clinicopathologic features of renal EAML and evaluated the prognostic significance. Among 78 angiomyolipoma (AML) patients, a total of 5 EAMLs were identified, accounting for 6.4% of the total AML cases. The mean age was 41.4 years, and the average tumor size was 12.7 cm in diameter. Association of tuberous sclerosis complex was identified in two cases. One EAML case showed malignant behavior with local recurrence and distant metastasis. The malignant EAML had a larger tumor size, a higher percentage of epithelioid component and atypical epithelioid cells, ≥2 mitoses per 10 high power fields with atypical mitosis, necrosis, extrarenal extension, and carcinoma-like growth pattern. Furthermore, the malignant case revealed p53 immunoreactivity and decreased membranous E-cadherin expression. Pathologic evaluation of adverse prognostic factors will be helpful for risk stratification and prognosis estimation of EAML patients.

Tuberous sclerosis complex: Hamartin and tuberin expression in renal cysts and its discordant expression in renal neoplasms

Tuberous sclerosis complex (TSC) results from mutation of TSC1 or TSC2 that encode for hamartin and tuberin. It affects the kidneys often in advance of extra-renal stigmata. We studied 14 TSC cases, and 4 possible TSC cases with multiple angiomyolipomas (AMLs) for hamartin and tuberin protein expression to determine if the staining profile could predict mutation status or likelihood of TSC with renal-limited disease. The 18 cases included 15 nephrectomies and 1 section of 6 TSC-associated renal cell carcinomas (RCC). Controls included the non-neoplastic kidney in 5 tumor nephrectomies, 4 sporadic cases of AML and 6 clear cell RCCs. In the 14 TSC cases, 9 had AMLs, 9 had RCCs, 5 had polycystic kidney disease and 8 had eosinophilic cysts (EC) lined by large eosinophilic cells. The controls and study cases showed luminal staining of proximal tubules (PT) and peripheral membrane staining in distal tubules/collecting ducts for hamartin and cytoplasmic staining for tuberin. Eosinophilic cysts had a luminal PT-like stain with hamartin and a cytoplasmic reaction for tuberin. Hamartin stained myoid cells in all AMLs. Tuberin was negative in all but 1AML, an epithelioid AML. All but 1 RCC were positive for tuberin; 13 RCCs (7 TSC/6 non-TSC) were negative for hamartin and 4 showed a weak reaction. We conclude that the ECs of TSC are proximal tubule-derived. The hamartin and tuberin staining profiles of AMLs and most RCCs are reciprocal precluding prediction of the mutation in TSC, and fail to predict if a patient with multifocal AML has TSC.

Angiomyolipoma and Malignant PEComa: Discussion of Two Rare Adrenal Tumors

Angiomyolipoma and PEComa are rare tumors descending from perivascular epithelial cells (PECs), with distinctive IHC, morphological, and ultrastructural features. The kidney is the most frequent site of origin, but not the only one; however, adrenal gland angiomyolipomas are extremely rare. We describe two cases being found in the adrenal glands. Given the paucity of literature on the subject, more information on this disease is necessary for diagnosis and treatment. Here, we describe two complete case reports, from presentation to treatment and follow-up, along with imaging and microscopic pathology samples, and provide a comprehensive review as to the history and current literature available regarding these extremely rare tumors.

MiT Family Translocation-Associated Renal Cell Carcinoma: A Contemporary Update With Emphasis on Morphologic, Immunophenotypic, and Molecular Mimics

Translocation-associated renal cell carcinoma (t-RCC) is a relatively uncommon subtype of renal cell carcinoma characterized by recurrent gene rearrangements involving the TFE3 or TFEB loci. TFE3 and TFEB are members of the microphthalmia transcription factor (MiT) family, which regulates differentiation in melanocytes and osteoclasts, and MiT family gene fusions activate unique molecular programs that can be detected immunohistochemically. Although the overall clinical behavior of t-RCC is variable, emerging molecular data suggest the possibility of targeted approaches to advanced disease. Thus, distinguishing t-RCC from its morphologic, immunophenotypic, and molecular mimics may have important clinical implications. The differential diagnosis for t-RCC includes a variety of common renal neoplasms, particularly those demonstrating clear cell and papillary features; in addition, because of immunophenotypic overlap and/or shared molecular abnormalities (ie, TFE3 gene rearrangement), a distinctive set of nonepithelial renal tumors may also warrant consideration. Directed ancillary testing is an essential aspect to the workup of t-RCC cases and may include a panel of immunohistochemical stains, such as PAX8, pancytokeratins, epithelial membrane antigen, carbonic anhydrase IX, HMB-45, and Melan-A. Dual-color, break-apart fluorescent in situ hybridization for TFE3 or TFEB gene rearrangement may be helpful in diagnostically challenging cases or when molecular confirmation is needed.

Predictive Value of Chemical-Shift MRI in Distinguishing Clear Cell Renal Cell Carcinoma From Non-Clear Cell Renal Cell Carcinoma and Minimal-Fat Angiomyolipoma

OBJECTIVE

The purpose of this study was to evaluate the diagnostic performance of chemical-shift MRI in the differentiation of clear cell renal cell carcinoma (RCC) from minimal-fat angiomyolipoma (AML) and non-clear cell RCC.

MATERIALS AND METHODS

In this retrospective study, 97 patients with solid renal tumors without macroscopic fat and with a pathologic diagnosis of clear cell RCC (n = 40), non-clear cell RCC (n = 31), or minimal-fat AML (n = 26) who had undergone renal chemical-shift MRI were included. Size, location, morphology, and signal intensity (SI) of the tumors and the contralateral normal kidneys on T2-weighted and in-phase and opposed-phase images were recorded by readers blinded to the pathology. Percentage tumor-to-renal parenchymal SI drop (percentage SI drop) was calculated and correlated to tumor histology. The statistical analysis was done using Kruskal-Wallis, one-way ANOVA, chi-square, and Fisher exact tests.

RESULTS

The percentage SI drop was significantly higher in clear cell RCC compared with non-clear cell RCC and minimal-fat AML (p < 0.001). Percentage SI drop of greater than 20% had 57.5% sensitivity, 96.5% specificity, and 92% positive predictive value (PPV); and percentage SI drop greater than 29% had 40% sensitivity and 100% specificity for diagnosis of clear cell RCC within the cohort of clear cell RCC, minimal-fat AML, and non-clear cell RCC. A significant proportion of minimal-fat AML (46.2%) displayed homogeneous low T2-weighted SI as opposed to clear cell RCC (5%) and non-clear cell RCC (29%) (p < 0.001).

CONCLUSION

The percentage SI drop on chemical-shift MRI had high specificity and moderate sensitivity in predicting clear cell RCC over non-clear cell RCC and minimal-fat AML. A percentage SI drop greater than 20% in a renal mass without macroscopically visible fat has high PPV for clear cell RCC over minimal-fat AML and non-clear cell RCC. Among morphologic features, homogeneous low T2 SI favors minimal-fat AML over RCC.

Rates of interventional procedures in patients with tuberous sclerosis complex-related renal angiomyolipoma

OBJECTIVE

To describe rates of renal artery embolization, partial nephrectomy, and complete nephrectomy in patients with tuberous sclerosis complex (TSC) and renal angiomyolipoma.

METHODS

Data from the MarketScan® Research Databases were used to select patients with TSC and renal angiomyolipoma during January 1, 2000-March 31,2013 (Commercial database) and January 1, 2000-June 30, 2012 (Medicaid database). Patients had at least 30 days of follow-up and were followed until the earliest of inpatient death, end of enrollment, or end of study. Rates of embolization and nephrectomy were calculated.

RESULTS

In total, 218 patients <18 years (mean = 9.7 years) and 378 patients ≥18 years (mean 36.9 years) were selected from the Commercial database. Fifty-nine patients <18 years (mean = 7.2 years) and 117 patients ≥18 years (mean = 37.2 years) were selected from the Medicaid database. Follow-up in the Medicaid cohorts was approximately twice that of the Commercial cohorts. Among patients in the study, 24.2% had at least one interventional procedure: 15.2% had embolization, 5.2% had partial nephrectomy, and 7.6% had complete nephrectomy. Within the Commercial cohort ≥18 years, 18.5% had embolization, 7.7% had partial nephrectomy, and 11.4% had complete nephrectomy. Corresponding percentages in the Medicaid adult cohort were 17.1%, 5.1%, and 4.3%. Repeat embolization procedures occurred in up to 7.7% of Commercial patients and in up to 6.8% of Medicaid patients. Repeat partial nephrectomy occurred in up to 4.5% and 1.7% of Commercial and Medicaid patients, respectively.

CONCLUSIONS

Approximately 25% of patients with TSC-renal angiomyolipoma experienced embolization or nephrectomy, with some patients undergoing repeat procedures. Study limitations included small sample sizes, the majority of the study period occurred prior to the approval of mammalian target of rapamycin inhibitors for the treatment of TSC-renal AML, and results may not be generalizable to patients with insurance other than commercial or Medicaid.

Imaging features of tuberous sclerosis complex with autosomal-dominant polycystic kidney disease: a contiguous gene syndrome

BACKGROUND

Genes for tuberous sclerosis complex (TSC) type 2 and autosomal-dominant polycystic kidney disease (ADPKD) type 1 are both encoded over a short segment of chromosome 16. When deletions involve both genes, an entity known as the TSC2/ADPKD1 contiguous gene syndrome, variable phenotypes of TSC and ADPKD are exhibited. This syndrome has not been reviewed in the radiology literature. Unlike renal cysts in TSC, cystic disease in TSC2/ADPKD1 contiguous gene syndrome results in hypertension and renal failure. A radiologist might demonstrate polycystic kidney disease before the patient develops other stigmata of TSC. Conversely, in patients with known TSC, enlarged and polycystic kidneys should signal the possibility of the TSC2/ADPKD1 contiguous gene syndrome and not simply TSC. Distinguishing these diagnoses has implications in prognosis, treatment and genetic counseling.

OBJECTIVE

To describe the clinical and imaging findings of tuberous sclerosis complex and polycystic kidney disease in seven pediatric patients.

MATERIALS AND METHODS

We retrospectively reviewed renal and brain imaging of children and young adults with genetically proven or high clinical suspicion for TSC2/ADPKD1 contiguous gene syndrome.

RESULTS

We included seven pediatric patients from two referral institutions. Ages ranged from birth to 21 years over the course of imaging. The mean follow-up period was 9 years 8 months (4 years 6 months to 20 years 6 months). No child progressed to end-stage renal disease during this period. Three patients were initially imaged for stigmata of TSC, three for abdominal distension and one for elevated serum creatinine concentration. All patients developed enlarged, polycystic kidneys. The latest available imaging studies demonstrated that in 12 of the 14 kidneys 50% or more of the parenchyma was ultimately replaced by >15 cysts, resulting in significant cortical thinning. The largest cysts in each kidney ranged from 2.4 cm to 9.3 cm. Echogenic lesions were present in 13 of the 14 kidneys, in keeping with angiomyolipomas (ranging from 0.4 cm to 7.8 cm). Compared to the latest imaging studies, the initial studies only demonstrated 64% of kidneys to be borderline or enlarged; the majority had 10 or more cysts and 0-5 echogenic foci in each kidney, measuring 0.8 cm maximally, which were possible angiomyolipomas. Increased cortical echogenicity was observed in eight kidneys, and decreased corticomedullary differentiation was demonstrated in six kidneys. Cortical thinning varied with size and number of cysts.

CONCLUSION

The sonographic renal findings in TSC2/ADPKD1 contiguous gene syndrome progress over time and demonstrate a specific pattern of renal disease different from typical tuberous sclerosis complex. There are multiple cysts at presentation and there is progressive enlargement of the kidneys and of the renal cysts. Because clinical or imaging findings of TSC may not manifest in the young child, the radiologist can be the first to suggest a diagnosis of TSC2/ADPKD1 contiguous gene syndrome and recommend thorough skin examination and imaging in search of TSC findings. The radiologist should be able to suggest the diagnosis of TSC2/ADPKD1 contiguous gene syndrome in children with TSC who have large cysts occupying a large portion of an enlarged kidney. This should not be dismissed as renal cystic disease of TSC or as ADPKD because the diagnosis of TSC2/ADPKD1 contiguous gene syndrome has implications for patient management and prognosis.

Tuberous sclerosis-associated renal cell carcinoma: a clinicopathologic study of 57 separate carcinomas in 18 patients

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder with characteristic tumors involving multiple organ systems. Whereas renal angiomyolipoma (AML) is common in TSC, renal cell carcinoma (RCC) is rarely reported. Fifty-seven RCCs from 13 female and 5 male TSC patients were reviewed. Age at surgery ranged from 7 to 65 years (mean: 42 y). Nine patients (50%) had multiple synchronous and/or metachronous RCCs (range of 2 to 20 RCCs) and 5 had bilateral RCCs (28%). Seventeen patients (94%) had histologically confirmed concurrent renal AMLs, including 15 with multiple AMLs (88%) and 9 (50%) with AMLs with epithelial cysts. None of the 15 patients with available clinical follow-up information had evidence of distant metastatic disease from 6 to 198 months after their initial surgery (mean: 52 mo). The 57 RCCs exhibited 3 major distinct morphologies: (1) 17 RCCs (30%) had features similar to tumors previously described as "renal angiomyoadenomatous tumor" or "RCC with smooth muscle stroma"; (2) 34 RCCs (59%) showed features similar to chromophobe RCC; and (3) 6 RCCs (11%) showed a granular eosinophilic-macrocystic morphology. Distinct histologic changes were also commonly present in the background kidney parenchyma and included cysts or renal tubules lined by epithelial cells with prominent eosinophilic cytoplasm, nucleomegaly, and nucleoli. Immunohistochemically, all RCCs tested showed strong nuclear reactivity for PAX8 and HMB45 negativity. Compared with sporadic RCCs, TSC-associated RCCs have unique clinicopathologic features including female predominance, younger age at diagnosis, multiplicity, association with AMLs, 3 recurring histologic patterns, and an indolent clinical course. Awareness of the morphologic and clinicopathologic spectrum of RCC in this setting will allow surgical pathologists to better recognize clinically unsuspected TSC patients.

[Guidelines for the management of tuberous sclerosis complex renal disease]

PURPOSE

To review existing literature and deduce guidelines for the management of renal disease in patients with tuberous sclerosis complex (TSC).

PATIENTS

After review of literature, a core panel of five physicians wrote a draft that was evaluated by 14 reviewers who used a 9-level scale (1: total disagreement; 9: total agreement). The guidelines were then reformulated until each item received a median score superior or equal to 8.

RESULTS

Forty-eight to 80 % of TSC patients have significant renal involvement including angiomyolipomas (AMLs), cysts, malignant tumors and renal insufficiency. It is recommended to perform an abdominal ultrasound (and serum creatinine if abnormal ultrasound) when TSC is diagnosed. This work-up will be repeated every 3-5years if normal. Associated autosomal dominant polycystic kidney disease must be suspected in case of numerous and large cysts. After the age of 20, follow-up should use computed tomography (CT) or MRI that are more precise than ultrasound for the measurement of AMLs. Biopsy of a renal mass should be discussed in case of calcifications, necrosis or rapid growth. Females with TSC should undergo screening for pulmonary lymphangioleiomyomatosis by CT at the age of 18, and, if negative at the age of 30-40. Acute bleeding should be treated with percutaneous embolization. Asymptomatic angiomyolipomas with several risk factors (size>80mm, predominant vascular component, micro-aneurysms) should undergo prophylactic treatment, if possible using embolization. The role of mTOR inhibitors in the management of angiomyolipomas needs to be defined.

CONCLUSION

Standardization of follow-up and treatment is necessary to improve the management of TSC renal involvement.

Incidental monotypic (fat-poor) renal angiomyolipoma diagnosed by core needle biopsy

We present the case of a 55-year-old patient with a history of chemotherapy and bone marrow transplantation because of acute myeloid leukaemia. An incidental 4 × 3 cm measuring renal mass was detected while performing a magnetic resonance imaging (MRI) for lumbago. The lesion was suspected to be either a renal cell carcinoma (RCC) or a leukemic infiltration. To decide about further treatment a percutaneous core needle biopsy was performed. Histology showed a monotypic angiomyolipoma, a relatively rare benign renal lesion. Interestingly, in cross-sectional imaging, angiomyolipoma was not taken into differential diagnostic account because of lack of a fatty component. Due to bleeding after biopsy the feeding artery of the tumor was occluded by microcoils. This case demonstrates the utility of biopsy of renal tumors, in particular when small tumor-like lesions are incidentally detected to decide about the right treatment and thereby avoiding nephrectomy.

Clinical and molecular insights into tuberous sclerosis complex renal disease

Patients with tuberous sclerosis complex are at great risk of developing renal lesions as part of their disease. These lesions include renal cysts and tumors. Significant advances in understanding the cell biology of these renal lesions has already led to clinical trials demonstrating that pharmacological interventions are likely possible. This review focuses on the pathology of these renal lesions, their underlying cell biology, and the possible therapeutic strategies that may prove to significantly improve care for these patients.

Epithelioid angiomyolipoma: imaging appearances

Epithelioid angiomyolipoma is a recently described rare variant of renal angiomyolipoma. It can occur in patients with or without tuberous sclerosis, and may potentially be malignant. We report the imaging findings from two cases of epithelioid angiomyolipoma: the first in a patient with tuberous sclerosis complex, arising in a horse-shoe kidney and growing into the inferior vena cava and right atrium; the second in a 62-year-old hypertensive man.

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.

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.

Angiomyolipoma With Epithelial Cysts (AMLEC)

Renal angiomyolipoma (AML) is typically a solid lesion, composed of varying amounts of adipose, vascular, and muscular tissue, lacking an epithelial component. Although it is known that entrapped renal tubules may be observed in AML, presentation as a cystic mass has not been previously reported. We report the clinicopathologic and immunohistochemical features of four cystic renal AML. The lesions were found in 2 male and 2 female patients, ranging in age from 37 to 76 years, none with a history of hormonal therapy. One of the four patients had known tuberous sclerosis, and this patient and 1 other presented with bilateral cystic renal lesions. Grossly, the lesions measured between 1.3 and 4.5 cm in greatest dimension. Histologically, the lesions were each composed of three components: 1) epithelial cysts lined by cuboidal to hobnail cells; 2) a compact subepithelial "cambium-like" layer of cellular, müllerian-like AML stroma with prominent admixed chronic inflammation; and 3) muscle-predominant AML with associated dysmorphic blood vessels exterior to the cellular subepithelial stroma. Immunohistochemically, the stromal components of all four lesions labeled with HMB-45 and Melan-A, most intensely in the cellular subepithelial stroma, whereas smooth muscle actin and desmin demonstrated the opposite pattern, with greatest intensity in the muscle-predominant AML areas. Immunoreactivity for estrogen and progesterone receptors (ER, PR) and CD10 was present in all cases, with strongest and most diffuse staining in the subepithelial AML cells. The cyst lining cells were positive for pancytokeratin and soy bean agglutinin (the latter characteristic of distal nephron epithelium) but did not label for ER, PR, or melanocytic markers. Although these distinctive lesions may be confused with mixed epithelial-stromal tumor, their lack of female predominance or association with hormone therapy, their distinctive dysplastic blood vessels and disorganized exterior muscular layer, along with their immunohistochemical profile, support their classification as AML with epithelial cysts. Whereas the cysts appear to arise primarily from entrapped collecting ducts, the peculiar subepithelial condensation of AML stromal cells, with morphologic and immunohistochemical features suggesting differentiation toward endometrial stroma, may represent epithelial-induced müllerian differentiation not previously reported in AML.

Magnetic Resonance Imaging of Adrenal Angiomyolipoma

Angiomyolipoma is a benign mesenchymal neoplasm that typically occurs in the kidney sporadically or in patients with tuberous sclerosis complex. Extrarenal angiomyolipomas are uncommon, and the liver is the most common extrarenal site. Other sites reported include the bone, colon, heart, lung, parotid gland, skin, spermatic cord, gynecologic regions, and retroperitoneum. A case of an angiomyolipoma involving the right adrenal gland in a 49-year-old female patient with tuberous sclerosis is reported. The magnetic resonance (MR) imaging features are also discussed. Only 2 cases describing adrenal angiomyolipoma were found in the English literature. Neither of these 2 cases was documented in the radiology literature or discussed the MR features of adrenal angiomyolipoma.