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Aims: To determine the significance of the epithelioid type and the corresponding molecular alterations in hepatic angiomyolipoma (AML)., Methods and Results: We retrieved 24 samples of hepatic AML to delineate the clinicopathological features and the immunohistochemical expression of components in the mTOR pathway, and employed microsatellite markers to analyse allelic imbalances in the TSC1 and TSC2 regions. Myomatous AML was the most common type, and a predominantly epithelioid cell population was observed in 50% of the samples. Two-thirds of all samples contained <20% of fat tissue. Four cases of monotypic epithelioid AML were discovered without prognostic implications. Elevated phospho-p70S6 kinase expression was noted in 19 samples in the absence of phospho-AKT activity. Loss of heterogeneity (LOH) of TSC1/TSC2 was found in 15 samples. As compared wityh syndromic AML samples, sporadic AML samples showed LOH of microsatellite markers to a limited extent. Only four samples had increased β-catenin expression in the context of concurrent high expression of phospho-p70S6 kinase and phospho-S6 (P = 0.018)., Conclusions: The low fat content and epithelioid cytomorphology in hepatic AML potentially obstruct preoperative and pathological diagnosis. Alteration of the mTOR pathway and LOH of the tuberous sclerosis complex genes is a frequent pathogenesis in hepatic AMLs., (© 2014 John Wiley & Sons Ltd.)

Renal epithelioid angiomyolipoma (EAML) is a potentially malignant tumor type whose characteristics and biomarkers predictive of malignant behavior have not been elucidated. Here, we report three cases of renal EAML with malignant features but without histories of tuberous sclerosis complex. Case 1 involved a 29-year-old man with a 12-cm solid mass in the right kidney who underwent radical right nephrectomy. Case 2 involved a 22-year-old woman with a retroperitoneal mass who underwent radical right nephrectomy and retroperitoneal tumorectomy. Local recurrence was detected 7 years post-surgery. Case 3 involved a 23-year-old man with a 14-cm solid mass in the left kidney who underwent radical left nephrectomy. Microscopically, the tumors in all cases demonstrated proliferation of epithelioid cells with atypia, mitotic activity, necrosis, hemorrhage, and vascular invasion. Epithelioid cells in all cases were immunohistochemically positive for melanocytic and myoid markers and weakly positive for E-cadherin and β-catenin. Immunohistochemistry revealed activation of the mammalian target of rapamycin pathway. Here, we report the morphological and immunohistochemical features of clinically or histologically malignant renal EAML., (© 2014 The Authors. Pathology International © 2014 Japanese Society of Pathology and Wiley Publishing Asia Pty Ltd.)

Renal angiomyolipoma (AML) may present as rare variants such as epithelioid and AML with epithelial cysts posing difficulties for the diagnosis to the surgical pathologist. We report a case of a 46-year-old male patient presenting a 5-cm solid tumor in the lower pole of the left kidney, with cystic changes at cut surface. The tumor exhibited 95% of epithelioid cells with atypical nuclei. A small focus of typical AML was observed. The immunoprofile of tumor cells was classical of AML including expression of melanocytic markers such as HMB45 and Melan A. We report the immunohistochemical study of the cystic component in an epithelioid AML. In contrast to the immunoreactivity reported in typical AML, the present case shows obvious expression of melanocytic markers in the cystic epithelial lining. This is strong evidence that these cysts are neoplastic and derived from AML, rather than entrapped native collecting duct epithelium., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Epithelioid angiomyolipomas (AMLs) of the liver are rare tumors with imaging and cytologic features overlapping with those of hepatocellular carcinomas. We report the fine needle aspiration and core biopsy findings of an epithelioid AML in the right hepatic lobe of a 32-year-old female with tuberous sclerosis. She had undergone renal transplantation 8 years previously after bilateral nephrectomy for renal AMLs and a 3-cm chromophobe renal cell carcinoma. Hepatocellular carcinoma was suspected during the initial cytologic and histologic examination based on the presence of numerous large polygonal cells with ample finely vacuolated or granular cytoplasm, low nucleocytoplasmic ratio, and mild nuclear pleomorphism in the smears, as well as a distinctive trabecular histologic pattern in the core biopsies. Immunoperoxidase stains showed that the neoplastic cells were negative for cytokeratins and positive for HMB45, Melan-A, and smooth muscle actin, establishing the diagnosis of epithelioid AML. To determine the distinguishing cytomorphologic features between epithelioid AML and HCC, we have compared the cytologic features of 15 cases of hepatic AML reported in the literature, including the present case, to the FNA cytologic findings of 38 consecutive cases of HCC diagnosed at out institution., (Copyright © 2011 Wiley Periodicals, Inc.)

Renal epithelioid angiomyolipoma (EAML) is a rare but distinct variant of angiomyolipoma, closely simulating renal cell carcinoma or sarcoma both clinically and histopathologically. This report presents an unusual case of unilateral simultaneous renal EAML and renal clear cell carcinoma. A 52-year-old man without any sign of tuberous sclerosis had a complaint of 6-month history of pain in left renal area and had macroscopic hematuria twice within the recent 1 month. Computed tomography showed the presence of 2 masses in the upper and lower portion of the left kidney. The patient underwent left radical nephrectomy. Histological examination revealed the upper mass was composed of medium to large epithelioid cells with clear or eosinophilic cytoplasm and numerous giant multinucleated cells. Adult-appearing adipose tissue and coagulative necrosis could also be observed focally in the mass. Immunohistochemically, the tumor cells in the upper mass showed positive reactions to actin, HMB-45, Melan-A, and CD68 but negative reactions to pan-cytokeratin (pan-CK), epithelial membrane antigen, and CD10. However, the lower mass was composed of diffusely monomorphic clear cells with strongly immunoreactive for pan-CK, vimentin, and CD10, whereas without expression for HMB-45 and actin. The patient showed no evidence of recurrence or metastasis during 1-year postoperative following-up period. To the authors' knowledge, this is the first report of coincidental renal EAML and clear cell carcinoma in the same kidney. Unlike classic triphasic angiomyolipoma, adjuvant therapy after resection should be considered for renal EAML because of its malignant potential, more aggressive behavior and poor prognosis.

This review examines the histopathologic, immunohistochemical, ultrastructural, and molecular biologic features of epithelioid angiomyolipoma (EAML), with an emphasis on the differential diagnosis of intra-abdominal EAML. Epithelioid angiomyolipoma is an uncommon mesenchymal tumor with malignant potential, frequently associated with tuberous sclerosis complex. Histologically, EAML is characterized by sheets or nests of large polygonal epithelioid cells with abundant eosinophilic or occasionally clear cytoplasm, often with prominent nucleoli, and EAML may include multinucleated and markedly pleomorphic forms. As these tumors share a distinctive perivascular epithelioid cell phenotype, they belong to the PEComa tumor family. Nearly all EAMLs show immunoreactivity for both melanocytic and myoid markers. Ultrastructurally, EAMLs show evidence of melanogenesis by the presence of premelanosomes. Epithelioid angiomyolipoma can pose significant diagnostic challenges as it mimics morphologically a variety of neoplasms including renal cell carcinoma, renal oncocytoma, adrenal cortical neoplasm, epithelioid smooth muscle tumor, epithelioid peripheral nerve sheath tumor, epithelioid gastrointestinal stromal tumor, epithelioid melanoma, hepatoblastoma, and hepatocellular carcinoma. The variation in immunophenotype in these tumors requires a prudent use of immunohistochemistry, which may occasionally need complementation by electron microscopy to establish the correct diagnosis.

Objective: To study the pathologic features and immunophenotype of 3 cases of melanotic epithelioid clear cell tumor of kidney., Methods: More than 2000 cases of renal tumors were retrospectively reviewed. Three cases of melanotic epithelioid clear cell tumor were identified. Immunohistochemical study was carried out using the paraffin-embedded tissue samples. Electron microscopy was also performed in 1 case., Results: Amongst the 3 cases studied, the male-to-female ratio is 1:2. Histologically, 2 cases showed a clear cell carcinoma-like pattern. Papillary structures covered by clear cells and eosinophilic cells were observed in 1 case. Immunohistochemical study showed that the tumor cells in all cases expressed HMB 45. Two of them were also positive for Melan A. The staining for epithelial markers and S-100 protein was negative. Melanosomes were not identified by ultrastructural examination., Conclusions: Melanotic epithelioid clear cell tumor is a rarely seen neoplasm of kidney. There are some histologic overlaps with renal cell carcinoma, epithelioid angiomyolipoma and melanoma. Immunohistochemical study is useful in confirming the diagnosis. The tumor represents a morphologic variant of epithelioid angiomyolipoma.

Aims: Renal epithelioid angiomyolipoma (EAML) is only described in case reports or in multi-institutional small series. The aim was to report cases seen at our institution and to perform a meta-analysis based on a literature review., Methods and Results: Six EAML cases seen at our institution were reviewed and a meta-analysis performed using cases retrieved from a literature review. There were a total of 69 cases for review. The male:female ratio was 1:3. In the absence of areas of typical AML, useful features in distinguishing EAML from epithelial renal neoplasms include: extreme degree of cytological atypia, histiocytoid appearance, presence of melanocytic pigments, solid architecture with the absence of frequent areas of alveolar pattern, tubulo-papillary formation and scarring. A fatal outcome, distant or lymph node metastasis, venous invasion and local recurrence were considered as adverse events and occurred in 40% of cases over a period of follow-up of 3-60 months (mean 22.5 +/- 18 months). Tumours with an unfavourable outcome showing marked cytological atypia and extensive tumour necrosis were larger (135 +/- 43 mm) than those with a favourable outcome (79 +/- 50 mm) (P < 0.002), and predominantly occurred in men., Conclusions: Renal neoplasms with certain unusual features should be investigated immunohistochemically to rule out the possibility of EAML. The frequency of adverse outcome is lower in EAML than in renal cell carcinoma.

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.

We report a case of uterine perivascular epithelioid cell tumor (PEComa) with malignant histological features in a 59-year-old woman with tuberous sclerosis (TBS). The patient also had extrapulmonary lymphangioleiomyomatosis involving pelvic lymph nodes, myometrium, cervix, and ovary ("pecomatosis"). The uterine tumor measured 2.6 cm and had marked nuclear pleomorphism, necrosis, and 2 mitoses per 50 high-powered field, with an occasional atypical mitosis and infiltrative borders. The nonneoplastic myometrium, the cervical wall, and the hilum of the ovary had multiple clusters of bland-looking epithelioid clear cells that ranged from 1 to 5 mm (pecomatosis). The uterine tumor cells were positive for HMB-45 (90%), Melan-A (70%), smooth muscle actin (50%), and estrogen receptor (30%). Of the 16 pelvic lymph nodes excised, 3 were involved with lymphangioleiomyomatosis that was positive for HMB-45 and estrogen receptor. This is only the second reported PEComa associated with pecomatosis and the fourth PEComa described in a patient with TBS. The clinical significance of pecomatosis is still uncertain but seems to be seen only in patients with TBS.

Objective: To investigate the clinicopathologic features of tumors showing perivascular epithelioid cell differentiation (PEComas)., Methods: The clinicopathologic data of 39 cases pf angiomyolipoma (AML), 17 males and 22 females, with the primary focus in the kidney on 30 cases, in the liver in 4 cases, in the lung, uterus and broad ligament, abdominal wall, retroperitoneum, and nasal cavity in 1 case respectively, were analyzed. Immunohistochemistry (HIC) was used to detect the expression of pan-cytokeratin (CK), S-100 protein, smooth muscle actin (SMA), desmin, vimentin, HMB45, Melan-A, microphthalmia transcription factor (MiTF), CD117, and CD34 in the specimens of the tumors obtained during operation. Twenty patients were followed up., Results: Pathological examination showed branched capillaries or arterioles, often thick-walled similar to those in the renal cell carcinoma, and the cancerous cells consisting of the mixture of epithelial cells and spindle cells. HIC showed that the expression rates of Melan-A, HMB45, MITF, SMA, desmin, S-100 protein, vimentin, CD117, CK, and CD34 were 95% (37/39), 72% (32/39), 46% (18/39), 82% (32/39), 27% (10/39), 15% (6/39), 82% (32/39), 10% (4/39), 0, and 0 respectively. Clinical follow-up showed 1 patient alive with tumor, and 19 alive free from disease., Conclusion: PEComas have distinctive morphological and immunohistochemical features.

Angiomyolipoma (AML) belong to a family of tumors known as perivascular epithelioid cell tumors (PEComas) that share a common immunophenotypic profile of muscle and melanocytic differentiation. These tumors are clonal in nature and have a strong association with tuberous sclerosis. Genetic analyses have reported allelic imbalance at the TSC2 locus on 16p13. In the context of non-tuberous sclerosis complex (TSC), non-lymphangioleiomyomatosis-associated AMLs, and non-renal PEComas, the functional status of the TSC2 signaling pathway has not been reported. Studies over the last several years have uncovered a critical role of the TSC1/2 genes in negatively regulating the Rheb/mTOR/p70S6K cascade. Here, we examined the activity of this pathway in sporadic AMLs and PEComas using immunohistochemical and biochemical analyses. We found increased levels of phospho-p70S6K, a marker of mTOR activity, in 15 of 15 non-TSC AMLs. This was accompanied by reduced phospho-AKT expression, a pattern that is consistent with the disruption of TSC1/2 function. Western blot analysis confirmed mTOR activation concurrent with the loss of TSC2 and not TSC1 in sporadic AMLs. Similarly, elevated phospho-p70S6K and reduced phospho-AKT expression was detected in 14 of 15 cases of extrarenal PEComas. These observations provide the first functional evidence that mTOR activation is common to sporadic, non-TSC-related AMLs and PEComas. This suggests the possibility that mTOR inhibitors such as rapamycin may be therapeutic for this class of disease.

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.

Perivascular epithelioid cell tumor (PEComa) is a neoplasm composed chiefly of HMB-45-positive epithelioid cells with clear to granular cytoplasm and a perivascular distribution. Such tumors have been reported in different organs under a variety of designations. The cytogenetic features of these neoplasms have not been well studied. We collected 9 tumors (5 of kidney, 1 of prostate, 1 of urinary bladder, 1 of the pelvic cavity soft tissue, and 1 of uterus) from 8 patients, including one patient with tuberous sclerosis complex. The paraffin blocks of tumor tissue were submitted for comparative genomic hybridization analyses. Gross chromosomal aberrances were observed in all cases. The frequent imbalances were losses on chromosome 19 (8 cases), 16p (6 cases), 17p (6 cases), 1p (5 cases), and 18p (4 cases) and gains on chromosome X (6 cases), 12q (6 cases), 3q (5 cases), 5 (4 cases), and 2q (4 cases). The frequent deletion of 16p in which TSC2 gene is located indicates the oncogenetic relationship of PEComas with angiomyolipoma as a TSC2-linked neoplasm. From a molecular genetic perspective, the recurrent chromosomal alterations in both renal and extrarenal tumors further support the concept of PEComa as a distinctive tumor entity regardless of anatomic location.

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 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.

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.

Aims: Monotypic epithelioid angiomyolipoma is a distinct and definable variant of angiomyolipoma, composed of monomorphous epithelioid cells that show HMB45 immunoreactivity. Angiomyolipoma, including its morphological variants, belongs to the family of perivascular epithelioid cell tumour., Methods and Results: The tumour was examined using immunohistochemical staining and by transmission electron microscopy. Neoplastic cells showed a cytoplasmic granular positivity for HMB45., Conclusions: Extrarenal angiomyolipomas are rare and, to the best of our knowledge, this is the first reported case of a primary monotypic epithelioid angiomyolipoma of bone in a patient without evidence of tuberous sclerosis.

A recent case of angiomyolipoma (AML) with a prominent component of polygonal epithelioid cells is described. A 27-year-old Japanese male with tuberous sclerosis presented with massive abdominal tumors increasing progressively in size. The patient died of respiratory disturbance and the autopsy revealed massive tumors in the bilateral kidneys, liver and lymph nodes, subependymal giant cell glioma of the brain and lymphangiomyomatosis of the lungs. The giant tumors were an unusual type of AML with a component of polygonal epithelioid cells, which showed a hepatocellular carcinoma-like pattern in some areas. Smooth muscle components comprising spindle cells, short or plump spindle cells and polygonal epithelioid cells frequently exhibited positive staining for HMB-45 but negative staining for epithelial cell markers. The unusual AML presented in this case was thought to be of low-grade malignancy and slow growing. It has been suggested that angiomyolipomas with diffuse areas of epithelioid cell component are potentially malignant. Immunostainings positive for HMB-45 but negative for epithelial cell markers are considered to be useful in differentiating AML with polygonal epithelioid cell component from other tumors, especially from renal cell carcinoma and hepatocellular carcinoma.