Constant allelic alteration on chromosome 16p (TSC2 gene) in perivascular epithelioid cell tumour (PEComa): genetic evidence for the relationship of PEComa with angiomyolipoma

The evolving classification of soft tissue tumours - an update based on the new 2013 WHO classification

The new World Health Organization (WHO) classification of soft tissue tumours was published in early 2013, almost 11 years after the previous edition. While the number of newly recognized entities included for the first time is fewer than that in 2002, there have instead been substantial steps forward in molecular genetic and cytogenetic characterization of this family of tumours, leading to more reproducible diagnosis, a more meaningful classification scheme and providing new insights regarding pathogenesis, which previously has been obscure in most of these lesions. This brief overview summarizes changes in the classification in each of the broad categories of soft tissue tumour (adipocytic, fibroblastic, etc.) and also provides a short summary of newer genetic data which have been incorporated in the WHO classification.

Epithelioid angiomyolipoma of the kidney: pathological features and clinical outcome in a series of consecutively resected tumors

The 2004 World Health Organization classification of tumors defines epithelioid angiomyolipoma of kidney as a potentially malignant mesenchymal neoplasm with reported metastasis in approximately one-third of the cases. However, this conclusion was based primarily on individual case reports and small retrospective series. More recently reported larger series have shown varying results. We reviewed 437 consecutive renal angiomyolipomas with primary resection at three tertiary-care institutions with high nephrectomy volumes. Only tumors showing >80% epithelioid histology were included in this study. Tumors resected elsewhere and reviewed in consultation were not included. Twenty of these 437 (4.6%) were classified as epithelioid angiomyolipoma. The female to male ratio was 11:9, mean age 49.7 (range, 30-80) years, and mean tumor size 8.7 (range, 1-25) cm. Microscopic tumor necrosis was present in 10 (50%) tumors and mitotic activity (range, <1-5/10 high power fields) in 8 (40%); atypical mitoses were seen in only 1 (5%) tumor. Pleomorphic ganglion-like or multinucleated giant cells were seen in 18 (90%) tumors. With a mean follow-up of 82.5 (range, 1-356) months, seventeen patients were alive with no-evidence-of-disease at the time of last follow-up; two patients died of unrelated causes with no-evidence-of-disease, and one patient (5%) developed distant metastases. Our data, based on consecutively resected angiomyolipomas with long clinical follow-up, suggests that epithelioid angiomyolipomas constitute a small proportion of all angiomyolipomas, and the rate of aggressive behavior among epithelioid angiomyolipomas, even when showing morphologic features previously reported to portend aggressive clinical behavior, is very low.

Incidental perivascular epithelioid cell tumor in an inguinal hernia sac

Perivascular epithelioid tumors (PEComa) are uncommon mesenchymal neoplasms demonstrating positivity for muscular and melanocytic immuno-markers. Included in this category are angiomyolipoma, lymphangioleiomyomatosis, and clear cell sugar tumors. Lesions which do not fit into these categories are classified as "not otherwise specified". We present a case of an incidentally discovered PEComa within inguinal hernia sac contents in a 70-year-old woman. It consisted of spindled and epithelioid cells with bland oval nuclei, small nucleoli and clear to light eosinophilic cytoplasm. There was no atypia or mitoses. The lesion was strongly positive for HMB45 and smooth muscle actin. Pelvic soft tissue and peritoneal PEComas are rarely reported in literature and very little is known about their prognosis. We discuss the immunohistochemistry, differential diagnosis, and pathogenesis of PEComas.

Mesenchymal Tumors of the Gastrointestinal Tract Other than GIST

Mesenchymal tumors involve the gastrointestinal (GI) tract more frequently than other visceral organs. Many such tumors are small, and are benign and increasingly being detected incidentally during colonoscopic screening. Some tumors show distinctive features at this site, such as schwannoma and clear cell sarcoma-like tumor of the GI tract. Without knowledge of these features, recognition of these tumor types can be difficult. This reviews addresses recent developments and diagnostic features of mesenchymal tumors of the GI tract other than gastrointestinal stromal tumor (GIST).

Results of an international randomized phase III trial of the mammalian target of rapamycin inhibitor ridaforolimus versus placebo to control metastatic sarcomas in patients after benefit from prior chemotherapy

PURPOSE

Aberrant mammalian target of rapamycin (mTOR) signaling is common in sarcomas and other malignancies. Drug resistance and toxicities often limit benefits of systemic chemotherapy used to treat metastatic sarcomas. This large randomized placebo-controlled phase III trial evaluated the mTOR inhibitor ridaforolimus to assess maintenance of disease control in advanced sarcomas.

PATIENTS AND METHODS

Patients with metastatic soft tissue or bone sarcomas who achieved objective response or stable disease with prior chemotherapy were randomly assigned to receive ridaforolimus 40 mg or placebo once per day for 5 days every week. Primary end point was progression-free survival (PFS); secondary end points included overall survival (OS), best target lesion response, safety, and tolerability.

RESULTS

A total of 711 patients were enrolled, and 702 received blinded study drug. Ridaforolimus treatment led to a modest, although significant, improvement in PFS per independent review compared with placebo (hazard ratio [HR], 0.72; 95% CI, 0.61 to 0.85; P = .001; median PFS, 17.7 v 14.6 weeks). Ridaforolimus induced a mean 1.3% decrease in target lesion size versus a 10.3% increase with placebo (P < .001). Median OS with ridaforolimus was 90.6 weeks versus 85.3 weeks with placebo (HR, 0.93; 95% CI, 0.78 to 1.12; P = .46). Adverse events (AEs) more common with ridaforolimus included stomatitis, infections, fatigue, thrombocytopenia, noninfectious pneumonitis, hyperglycemia, and rash. Grade ≥ 3 AEs were more common with ridaforolimus than placebo (64.1% v 25.6%).

CONCLUSION

Ridaforolimus delayed tumor progression to a small statistically significant degree in patients with metastatic sarcoma who experienced benefit with prior chemotherapy. Toxicities were observed with ridaforolimus, as expected with mTOR inhibition. These data provide a foundation on which to further improve control of sarcomas.

Malignant perivascular epithelioid cell tumor of mesentery with lymph node involvement: a case report and review of literature

Perivascular epithelioid cell tumor (PEComa) is a rare but distinct mesenchymal neoplasm composed of histologically and immunohistochemically unique perivascular epithelioid cells. Due to its relative rarity, little is known about the histogenesis and prognostic factors of this tumor. We describe a case of unusual mesenteric PEComa in a 38-year-old female patient with regional lymph node involvement. Histologically, the tumor was composed of sheet of epithelioid cells with abundant clear or eosinophillic cytoplasms. Extensive coagulative necrosis and a few mitotic figures (2/50 high power field) could be found in tumor. The epithelioid tumor cells were diffusely positive for HMB-45, Melan-A, and focally positive for calponin. One of enlarged mesenteric lymph nodes was observed to be involved by tumor. A diagnosis of malignant mesenteric PEComa with lymph node involvement was made. The patient received chemotherapy after total resection of tumor and segmental resection of involved jejunum. There was no sign of recurrence of tumor found in period of 6-month regular follow-up after chemotherapy. To our knowledge, this is the first case of malignant PEComa in mesentery accompanied with regional lymph node involvement. The literature on this rare tumor is reviewed and diagnostic criteria of malignant PEComa are discussed.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1309992178882788.

Epithelioid angiomyolipoma of the kidney: radiological imaging

OBJECTIVES

To review the imaging findings of renal epithelioid angiomyolipomas.

METHODS

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

RESULTS

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

CONCLUSIONS

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

Extrarenal perivascular epithelioid cell tumors (PEComas) respond to mTOR inhibition: clinical and molecular correlates

Perivascular epithelioid cell tumors (PEComas) are a group of rare mesenchymal tumors that typically show both melanocytic and smooth muscle cell features. Some types of PEComa are seen at high frequency in tuberous sclerosis complex (TSC). The TSC1 and TSC2 genes are commonly mutated in both TSC-associated and sporadic PEComas, and mTOR signaling pathway activation is also common in these tumors. Preliminary reports have indicated that the mTOR inhibitors sirolimus and related drugs have activity in some patients with non-TSC-associated PEComa. Here, we report on the use of these medications in the treatment of five consecutive patients with extrarenal nonpulmonary PEComas seen at one institution. Three complete responses, one partial response and one case of progression were seen. Molecular studies identified TSC2 aberrations in four of these patients, and TFE3 translocation was excluded in the resistant case. A review of all published cases as well as those reported here indicates that partial or complete response was seen in 6 of 11 PEComas, with 5 of 6 having a complete response. These findings highlight the consistent though incomplete activity of mTOR inhibitors in the treatment of PEComas.

Successful treatment with the mTOR inhibitor everolimus in a patient with perivascular epithelioid cell tumor

Perivascular epithelioid cell tumor (PEComa) is an extremely rare neoplasm that appears to arise most commonly at visceral (especially gastrointestinal and uterine), retroperitoneal, and abdominopelvic sites. Malignant PEComas exist but are very rare. These tumors represent a family of mesenchymal neoplasms, mechanistically linked through activation of the mTOR signaling pathway. Metastatic PEComa is a rare form of sarcoma for which no effective therapy has been described previously and that has a uniformly fatal outcome. Although there is no known effective therapy, the molecular pathophysiology of aberrant mTOR signaling provides a scientific rationale to target this pathway therapeutically. The difficulty in determining optimal therapy, owing to the sparse literature available, led us to present this case. On this basis, we report a case of metastatic retroperitoneal PEComa treated with an oral mTOR inhibitor, with everolimus achieving significant clinical response.

Expression of E-cadherin in angiomyolipoma

Angiomyolipoma is the most common member of perivascular epithelioid cell tumors that characteristically express myogenic and melanocytic markers. E-cadherin is a calcium-dependent cell-cell adhesion molecule that is repressed in epithelial to mesenchymal transition occurring in carcinomas. E-cadherin has not, thus far, been systematically studied in angiomyolipoma. We analyzed a series of 42 angiomyolipomas with E-cadherin and discussed its clinicopathologic significance. Forty-two cases of angiomyolipomas (35 renal, 5 hepatic, and 2 retroperitoneal) were examined histologically. E-cadherin was investigated immunohistochemically and compared with other significant markers found in angiomyolipoma in all cases. The percentages of tumors staining positively were E-cadherin (98%), smooth muscle actin (98%), actin (93%), HMB-45 (93%), Melan-A (90%), S-100 (38%), and CD117 (60%). The intensity of E-cadherin staining was moderate to strong in 30 cases (71%). E-cadherin stained both the cytoplasm and cell membrane of tumor cells, but membrane staining was stronger in the epithelioid tumor cells than in the spindle-shaped tumor cells. E-cadherin may serve as an additional diagnostic marker for angiomyolipoma. Angiomyolipoma should be included in the differential diagnosis of E-cadherin-positive tumors. Stronger membrane immunoreactivity for E-cadherin in epithelioid tumor cells is possibly related to constitution of their epithelioid architecture, but the pathogenetic significance of E-cadherin in angiomyolipoma remains to be further studied.

Malignant perivascular epithelioid cell tumor in children: description of a case and review of the literature

Perivascular epithelioid cell tumors (PEComas) include different morphological entities originating from perivascular epithelioid cells. Their clinical behavior is not predictable, and there are no strict histologic criteria for malignancy, although larger tumors with infiltrative growth, hypercellularity, cellular atypia, atypical mitoses, and necrosis generally have a malignant course. Pediatric PEComas are rare, with less than 40 cases reported, mostly in children older than 5 years. We describe a case of malignant PEComa of the ligamentum teres in a 2-year-old girl, characterized by the occurrence of local relapse after primary treatment with chemotherapy and surgery and poor response to imatinib mesilate and temsirolimus used after further analyses confirmed p70S6K expression involved in the mTOR pathway. The girl was eventually treated with a debulking surgical procedure and is now alive with disease 6 years after diagnosis. Literature data of children affected by PEComas were also analyzed, trying to identify pathologic characteristics that could predict their course and therapeutic options. Histologically, they may be differentiated in 3 prognostic categories: (1) benign, lacking unfavorable morphological markers; (2) with uncertain malignant potential, carrying 1 unfavorable marker; and (3) malignant, with at least 2 unfavorable markers. In the literature, 9% of cases occurred as a second malignancy probably because of genomic instability related to treatment. Their different biology and the potential value of targeted therapies remain to be explored. The indolent evolution in our patient was similar to that reported in some other cases in the literature. In terms of treatment, the present case suggests a minor response to temsirolimus compared with the adult population.

"Malignant" perivascular epithelioid cell neoplasm: risk stratification and treatment strategies

Purpose. Perivascular epithelioid cell tumors (PEComas) are a rare collection of tumors characterized by a myomelanocytic phenotype, and PEComas occurring in “nonclassic” anatomic distributions are known as perivascular epithelioid cell tumor not otherwise specified (PEComa-NOS). This review aims to compile and analyze cases of PEComa-NOS in an effort to better define their natural history. Design. We evaluated all 234 cases of PEComa-NOS reported in the English literature, extracting information regarding diagnostic features, treatment approaches, and outcomes. Multivariate analysis of a number of variables evaluable on pathologic review was performed to refine preexisting risk stratification criteria. Outcomes for patients receiving nonsurgical treatment are also reported. Results. Primary tumor size ≥5 cm (P = 0.02) and a high (1/50 HPF) mitotic rate (P < 0.0001) were the only factors significantly associated with recurrence following surgical resection. Cytotoxic chemotherapy and radiation therapy have shown little benefit in treating PEComa-NOS; mTOR inhibition is emerging as a treatment option. Conclusion. Progress has been made in understanding the natural history and molecular biology of PEComa-NOS. This review further clarifies risk of recurrence in this disease, allowing clinicians to better risk stratify patients. Further work should focus on applying this knowledge to making treatment decisions for patients with this disease.

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.

Targeted therapy in sarcoma: should we be lumpers or splitters?

The identification of KIT as a critical driver in the pathogenesis of GI stromal tumor (GIST), and its subsequent inhibition with imatinib, have resulted in tremendous efforts to identify other potential therapeutic targets for the heterogeneous group of diseases known as sarcomas. Because of the rarity of sarcoma and the often limited number of patients per individual sarcoma subtype, clinical trials to date have often utilized unselected patient populations including multiple subtypes. Although this strategy increases the ease with which a particular trial may accrue patients, statistically significant therapeutic responses across an unselected patient population are often limited. Furthermore, in the absence of biologic correlatives, the identification of significant activity and subsequent interpretation of clinical trial results utilizing targeted therapies for this patient population have been challenging. However, hints have emerged, on the basis of preclinical and clinical observations, to suggest that certain targeted therapeutic approaches are appropriate in select histologic subtypes. This brief review will highlight data supporting the use of targeted therapy in both unselected and selected sarcoma patient populations.

Glucose deprivation in tuberous sclerosis complex-related tumors

Background

Cancer cells possess unique metabolic phenotypes that are determined by their underlying oncogenic pathways. Activation of the PI3K/Akt/mTOR signaling cascade promotes glycolysis and leads to glucose-dependence in tumors. In particular, cells with constitutive mTORC1 activity secondary to the loss of TSC1/TSC2 function are prone to undergo apoptosis upon glucose withdrawal in vitro, but this concept has not been tested in vivo. This study examines the effects of restricting glucose metabolism by pharmacologic and dietary means in a tuberous sclerosis complex (TSC) tumor xenograft model.

Results

Tumor-bearing mice were randomly assigned to receive unrestricted carbohydrate-free ("Carb-free") or Western-style diet in the absence or presence of 2-deoxyglucose (2-DG) in one of four treatment groups. After 14 weeks, tumor sizes were significantly different among the four treatment groups with those receiving 2-DG having the smallest tumors. Unexpectedly, the "Carb-free" diet was associated with the largest tumors but they remained responsive to 2-DG. PET imaging showed significant treatment-related changes in tumor ¹⁸fluorodeoxyglucose-uptake but the standard uptake values did not correlate with tumor size. Alternative energy substrates such as ketone bodies and monounsaturated oleic acid supported the growth of the Tsc2-/- cells in vitro, whereas saturated palmitic acid was toxic. Correspondingly, tumors in the high-fat, "Carb-free" group showed greater necrosis and liquefaction that contributed to their larger sizes. In contrast, 2-DG treatment significantly reduced tumor cell proliferation, increased metabolic stress (i.e., ketonemia) and AMPK activity, whereas rapamycin primarily reduced cell size.

Conclusions

Our data support the concept of glycolytic inhibition as a therapeutic approach in TSC whereas dietary withdrawal of carbohydrates was not effective.

Angiomyolipoma have common mutations in TSC2 but no other common genetic events

Renal angiomyolipoma are part of the PEComa family of neoplasms, and occur both in association with Tuberous Sclerosis Complex (TSC) and independent of that disorder. Previous studies on the molecular genetic alterations that occur in angiomyolipoma are very limited. We evaluated 9 angiomyolipoma for which frozen tissue was available from a consecutive surgical series. Seven of 8 samples subjected to RT-PCR-cDNA sequencing showed mutations in TSC2; none showed mutations in TSC1 or RHEB. Six of the seven mutations were deletions. We searched for 983 activating and inactivating mutations in 115 genes, and found none in these tumors. Similarly analysis for genomic regions of loss or gain, assessed by Affymetrix SNP6.0 analysis, showed no abnormalities. Loss of heterozygosity in the TSC2 region was commonly seen, except in patients with low frequency TSC2 mutations. We conclude that sporadic renal angiomyolipoma usually have mutations in TSC2, but not TSC1 or RHEB, and have no other common genomic events, among those we searched for. However, chromosomal translocations and gene fusion events were not assessed here. TSC2 inactivation by mutation is a consistent and likely necessary genetic event in the pathogenesis of most angiomyolipoma.

Therapeutic pipeline for soft-tissue sarcoma

INTRODUCTION

Soft-tissue sarcomas (STS) represent a heterogeneous group of malignant tumors originating from connective tissues. Over recent years, this heterogeneity has led to a molecular breakdown of STS and subsequent use of targeted agents in several molecularly defined subgroups. After the initial success of imatinib in gastrointestinal stromal tumors, several other compounds have shown promising activity in some but not all subgroups of sarcoma.

AREAS COVERED

This review discusses the rational and clinical results, when available, that support this subtype-directed approach. In the vast majority of cases, these agents have been tested only in patients with advanced disease; as chemotherapeutic agents are developed as non-histotype-specific therapies, they are not discussed here. The PubMed literature was searched using the terms 'sarcoma', 'angiogenesis', 'mTOR' and 'targeted agents'. Proceedings of the annual meeting of the American Society of Clinical Oncology as well as those of the Connective Tissue Oncology Society were also searched for relevant information.

EXPERT OPINION

Many agents are currently developed in a subtype-specific manner in STS and this represents a significant leap forward. However, much remains to be done to improve our understanding of the molecular biology of this heterogeneous group of diseases.

Perivascular epithelioid cell tumors (PEComas) of the head and neck: report of three cases and review of the literature

PEComas are a family of neoplastic lesions that share overlapping morphology, immunohistochemistry, and ultrastructure that include angiomyolipoma, lymphangioleiomyomatosis, clear cell "sugar" tumor of the lung as well as similar tumors occurring in a variety of visceral, cutaneous and soft tissue sites throughout the body. The defining histopathological features are epithelioid cells with a perivascular distribution containing clear to pale eosinophilic granular cytoplasm and a round-to-oval centrally located nucleus with an inconspicuous nucleolus. Immunohistochemically, coexpression of melanocytic (HMB-45 and/or Melan-A) and myoid markers are characteristic. In the present study, we describe three PEComas occurring in the head and neck (nasal cavity and larynx) and discuss the behavior of these distinctive tumors and review the literature of head and neck PEComas. The importance of recognizing this entity will ensure its consideration in the differential diagnosis of tumors of the head and neck with a similar morphology. The histogenesis of PEComas still remains elusive and additional cases with a prolonged follow up remain important to accurately determine the behavior of these distinctive tumors. Complete surgical excision still remains the treatment of choice for histologically benign PEComas.

Hepatic epithelioid angiomyolipoma with trabecular growth pattern: a mimic of hepatocellular carcinoma on fine needle aspiration cytology

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.

Novel targeted therapies in the treatment of soft-tissue sarcomas

Systemic therapy options for sarcomas historically have been limited once these tumors become resistant to traditional cytotoxic chemotherapy. Ongoing preclinical research into their biology and clinical trials based on rational biologic targeting have identified novel therapies. For example, the success of imatinib in gastrointestinal stromal tumor has led to the use of other tyrosine kinase inhibitors in other sarcoma subtypes. Other novel therapies include targeting of the mTOR pathway, and IGF-1 receptor. The heterogeneity of these tumors demands intelligently designed protocols in recognizing efficacy that may be restricted to certain histologic subtypes. This article will cover recent trials of new biologic agents in sarcomas that have exhibited promising activity.

Chromosomal alterations in Malaysian patients with nasopharyngeal carcinoma analyzed by comparative genomic hybridization

Nasopharyngeal carcinoma (NPC) is one of the most common cancers in Malaysia, mainly occurring among the Chinese population. To detect common genetic alterations in NPC, we screened seven cases of NPC using the comparative genomic hybridization (CGH) technique. Before proceeding to the CGH technique, the tumors were first confirmed to consist of 75% tumor cells or more. In brief, the technique consists of binding tumor DNA with normal DNA and human Cot-1 DNA, which is then hybridized to normal metaphase spreads. The slides were then counterstained with 4,6 diamino-2-phenylindole (DAPI II) for detection. Analyses were performed using CGH software (Cytovision). We found genetic alterations in all seven NPC samples. The common chromosomal gains (57%, four cases) were found on chromosome arms 1q, 4p, 5, 7q, 11, 14p, 15q, 18p, and 21p, and common chromosomal losses (43%, three cases) were found on chromosome arm 16p. Our results showed chromosomal alterations in all seven NPC cases in the Malaysian population. This result provides the platform for further investigations to locate tumor suppressor genes and oncogenes at specific chromosomal regions in Malaysian NPC patients.

Clinical features of lymphangioleiomyomatosis complicated by renal angiomyolipomas

OBJECTIVE

Renal angiomyolipomas (R-AMLs) are major complications of lymphangioleiomyomatosis (LAM). The objective of this study was to better understand the influence of R-AMLs in patients with LAM on the prognosis and other clinical factors related to respiration, and to investigate the management of R-AMLs in patients with LAM.

PATIENTS AND METHODS

We retrospectively investigated the clinical features of 7 patients with LAM [4 were TSC (Tuberous sclerosis complex)-LAM and 3 were S (sporadic)-LAM] complicated by R-AMLs admitted to our hospital from 1997 to 2008.

RESULTS

All patients were females and the mean age at diagnosis of LAM was 40.7 years (31.7 years for TSC-LAM and 52.7 years for S-LAM). Although 5 patients had symptoms related to R-AMLs, only 1 patient experienced symptoms related to R-AMLs at the time of diagnosis. Five patients had bilateral and 2 patients had unilateral R-AMLs. R-AMLs ruptured in 4 cases (3 patients were TSC-LAM) including 2 patients in whom they ruptured bilaterally, and who underwent bilateral nephrectomy. In 1 case, unilateral R-AMLs grew larger and appeared on the other side during the follow-up period.

CONCLUSION

Although only rare cases of LAM show symptoms related to R-AMLs initially, R-AMLs are a notable complication. To avoid nephrectomy, R-AMLs should be diagnosed when they are small and should be followed up carefully by periodic echograms or CT scans.

A distinctive subset of PEComas harbors TFE3 gene fusions

Perivascular epithelioid cell neoplasms (PEComas) include the common renal angiomyolipoma, pulmonary clear cell sugar tumor, lymphangioleiomyomatosis, and less common neoplasms of soft tissue, gynecologic, and gastrointestinal tracts. Recently, aberrant immunoreactivity for TFE3 protein (a sensitive and specific marker of neoplasms harboring TFE3 gene fusions) has been reported in as many as 100% of PEComas; however, TFE3 gene status in these neoplasms has not been systematically investigated. We used a fluorescence in situ hybridization (FISH) break-apart assay to evaluate for evidence of TFE3 gene fusions in archival material from 29 PEComas. These cases included 2 earlier published TFE3 immunoreactive nonrenal PEComas, 14 additional nonrenal PEComas, and 13 renal angiomyolipomas with predominantly spindle or epithelioid morphology. Four nonrenal PEComas (mean patient age 24 y) showed TFE3 gene rearrangements by FISH, and all 4 of these showed strong positive (3+) TFE3 immunoreactivity using the original validated overnight incubation protocol. Two of these cases had adequate mRNA for RT-PCR analysis, but neither harbored the PSF-TFE3 gene fusion reported earlier in 1 PEComa. In addition, a lung metastasis of a uterine PEComa showed TFE3 gene amplification, an earlier unreported phenomenon. None of the other 24 PEComas (mean patient age 54 y) showed TFE3 gene alterations, though 4 exhibited moderate positive (2+) TFE3 immunoreactivity. In contrast, using an automated stainer, 2 of these 4 cases exhibited strong (3+) TFE3 immunoreactivity. All PEComas with TFE3 genetic alterations immunolabeled strongly for Cathepsin K, similar to other PEComas. In conclusion, a subset of lesions currently classified as PEComas harbors TFE3 gene fusions. Although numbers are small, distinctive features of these cases include a tendency to young age, the absence of association with tuberous sclerosis, predominant alveolar architecture and epithelioid cytology, minimal immunoreactivity for muscle markers, and strong (3+) TFE3 immunoreactivity. Despite significant morphologic and immunohistochemical overlap with other PEComas, PEComas harboring TFE3 gene fusions may represent a distinctive entity.

An unresectable malignant perivascular epithelioid cell tumor resistant to multiple combined chemotherapies: a unique case report

Malignant perivascular epithelioid cell tumor (PEComa) was a kind of rare disease with malignant behavior and poor prognosis. Nearly all PEComas show immunoactivity for HMB45. The treatment strategy for malignant PEComa is still of controversy, especially in advanced or unresectable disease. We reported a 14-year-old patient of unresectable malignant PEComa, who was treated with multiple combined chemotherapies. The patient died of tumor 9 months after surgery, although 3 different combined chemotherapeutic regimens and antiangiogenic drug were used. Our case suggested that empirical chemotherapeutic regimens for soft tissue sarcomas might not be suitable for PEComa.

Molecular pathology of lymphangioleiomyomatosis and other perivascular epithelioid cell tumors

CONTEXT

Lymphangioleiomyomatosis (LAM) is a cystic lung disease that can be included in the wide group of proliferative lesions named PEComas (perivascular epithelioid cell tumors). These proliferative tumors are characterized by the coexpression of myogenic and melanogenesis-related markers. In all these lesions, genetic alterations related to the tuberous sclerosis complex (TSC) have been demonstrated. Striking improvements in the understanding of the genetic basis of this autosomal dominant genetic disease are coupled to the understanding of the mechanisms that link the loss of TSC1 (9q34) or TSC2 (16p13.3) genes with the regulation of the Rheb/m-TOR/p70S6K pathway. These data have opened a new era in the comprehension of the pathogenesis of LAM and have also suggested new therapeutic strategies for this potentially lethal disease.

OBJECTIVE

To present and discuss the pathologic and molecular features of LAM within the spectrum of PEComas, providing a rational approach to their diagnosis.

DATA SOURCES

The published literature and personal experience.

CONCLUSIONS

The inclusion of LAM within the PEComa category is supported by a variety of biologic data and can significantly help in providing a comprehensive view of this interesting and clinically relevant group of lesions. The demonstration of molecular alterations of the mTOR pathway in LAM and other PEComas represents a rational basis for innovative therapeutic approaches with inhibitors of mTOR signaling.

PEComas: a review with emphasis on cutaneous lesions

The connection between angiomyolipoma (AML) of the kidney, clear cell sugar tumor (CCST) of the lung, and pulmonary lymphangioleiomyoma (LAM), was progressively discovered because of the histologic and immunophenotypic similarities between the three tumors and their frequent association with tuberous sclerosis complex (TSC). Morphologically, analogous lesions found in other locations are composed of the unifying cell, the perivascular epithelioid cell (PEC). PEC tumors (or PEComas), other than AML, CCST, and LAM, are not associated with TSC and typically occur in middle-aged adult females. These neoplasms are composed of nests and fascicles of clear to granular epithelioid and/or spindled cells with a consistent arrangement around blood vessels. Characteristically, the cells express both melanocytic (usually HMB45) and myogenic (typically actin) markers. Although the most common sites are the gastrointestinal and genitourinary tracts, approximately 23 cases, to date, of PEComas arising in the skin have been reported. Primary cutaneous PEComas also have a predilection for adult females and most often present as a painless mass on the extremities. In contrast to other sites, the myogenic marker most commonly expressed in PEComas of the skin is desmin. Most reported cutaneous PEComas follow a benign course, however, a malignant case has been reported. Surgical excision is currently the mainstay of treatment.

Clinical activity of mTOR inhibition with sirolimus in malignant perivascular epithelioid cell tumors: targeting the pathogenic activation of mTORC1 in tumors

PURPOSE Perivascular epithelioid cell tumors (PEComas) represent a family of mesenchymal neoplasms, mechanistically linked through activation of the mTOR signaling pathway. There is no known effective therapy for PEComa, and the molecular pathophysiology of aberrant mTOR signaling provided us with a scientific rationale to target this pathway therapeutically. On this mechanistic basis, we treated three consecutive patients with metastatic PEComa with an oral mTOR inhibitor, sirolimus. PATIENTS AND METHODS Patients with advanced PEComa were treated with sirolimus and consented to retrospective collection of data from their medical records and analysis of archival tumor specimens. Tumor response was determined by computed tomography scans obtained at the clinical discretion of the treating physicians. Tumors were assessed for immunohistochemical evidence of mTORC1 activation and genetic evidence of alterations in TSC1 and TSC2. Results Radiographic responses to sirolimus were observed in all patients. PEComas demonstrated loss of TSC2 protein expression and evidence of baseline mTORC1 activation. Homozygous loss of TSC1 was identified in one PEComa. CONCLUSION Inhibition of mTORC1, pathologically activated by loss of the TSC1/TSC2 tumor suppressor complex, is a rational mechanistic target for therapy in PEComas. The clinical activity of sirolimus in PEComa additionally strengthens the pathobiologic similarities linking PEComas to other neoplasms related to the tuberous sclerosis complex.

Immunohistochemical and molecular genetic profiling of acquired cystic disease-associated renal cell carcinoma

AIMS

Acquired cystic disease-associated renal cell carcinoma (ACD-associated RCC) is a unique neoplasm that specifically develops in the background of acquired cystic disease of the kidney. The aim was to analyse nine ACD-associated RCCs from three patients to determine their immunohistochemical and molecular characteristics using immunohistochemistry, comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH).

METHODS AND RESULTS

ACD-associated RCC preferentially expressed proximal nephron phenotype (CD10+ /RCC marker+/alpha-methylacyl-CoA racemase+ /glutathione S-transferase-alpha+ /BerEP4+ /cytokeratin 7- /E-cadherin- /high-molecular-weight cytokeratin- /MOC31-). CGH combined with FISH demonstrated non-random chromosomal gains clustering on chromosomes 3 (8/9), 7 (6/9), 16 (7/9), 17 (4/9) and Y (5/9). Chromosomal losses were uncommon. The chromosomal aberrations in all multifocal tumours were not identical for the same kidney or for the same patient, indicating a 'field effect' that induces multiple independent clones.

CONCLUSIONS

Although the genetic profiles of ACD-associated RCC showed some similarity to those of papillary RCC, ACD-associated RCC distinctly revealed frequent gains on chromosomes 3 and Y. ACD-associated RCC is characterized not only by its particular clinical setting and histology, but also by its unique immunohistochemical and molecular genetic profiles.

Primary perivascular epithelioid cell tumor (PEComa) of the liver: report of a case

PEComa is very rare mesenchymal neoplasm which is formed by perivascular epithelioid cells and is characterized by dual melanocytic and myoid differentiation. Up to now only a very few cases of PEComa of the liver have been described worldwide. We herein present a patient who underwent a right hemihepatectomy for a huge tumor which could not be identified by imaging investigations. A final histopathologic examination revealed a benign epithelioid tumor with a solid growth pattern, abundant vascularity, and frequently dilated vascular channels. Immunohistochemically, the tumor cells were strongly positive for HMB-45, moderately positive for actin, and faintly positive for S-100, respectively. Based on the above findings, a diagnosis of a primary clear cell "sugar" tumor was established. Because the natural history of PEComas is mostly unpredictable, the patient has been closely followed up; however, no recurrence has so far been observed. Immunohistochemical findings play a crucial role in avoiding a misdiagnosis, and a surgical resection with an adequate margin of healthy tissue remains the gold standard of treatment. A long-term periodic follow-up is reasonable in all cases presenting with PEComa.

Perivascular epithelioid cell neoplasms: pathology and pathogenesis

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

A case of hepatic angiomyolipoma difficult to distinguish from hepatocellular carcinoma

We report a case of hepatic angiomyolipoma with uncommon clinical features. A 56-year-old man presented with a hepatic tumor in the caudate lobe. The tumor was hypoechoic on ultrasonography, showed early-phase hyperattenuation on enhanced computed tomography and did not absorb iron on superparamagnetic iron oxide-enhanced magnetic resonance imaging. Hepatocellular carcinoma was highly suspected, and the patient underwent hepatic resection. Histologically, the tumor was mainly composed of smooth muscle cells and contained small amounts of adipose cells and blood vessels. On immunohistochemical staining, the smooth muscle cells were positive for a melanocytic cell-specific monoclonal antibody. In cases with uncommon features of angiomyolipoma, it is quite difficult to distinguish angiomyolipoma from hepatocellular carcinoma.

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.

The pathogenesis and imaging of the tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an autosomal-dominant disorder characterized by the formation of hamartomatous lesions in multiple organ systems. It is the second most common neurocutaneous syndrome after neurofibromatosis type 1 and has been recognized since the late 1800s. Although the disease has complete penetrance, there is also high phenotypic variability: some patients have obvious signs at birth, while others remain undiagnosed for many years. In addition to skin lesions, TSC patients develop numerous brain lesions, angiomyolipoma (AMLs), lymphangiomyomatosis (LAM) in the lungs, cardiac rhabdomyomas, skeletal lesions, and vascular anomalies, all of which are well seen with medical imaging. Our knowledge of TSC genetics and pathophysiology has expanded dramatically in recent years: two genetic loci were discovered in the 1990s and recent elucidation of TSC's interaction with the mTOR pathway has changed how we manage the disease. Meanwhile, medical imaging is playing an increasingly important role in the diagnosis, management, and treatment of TSC. We provide an update on the genetics and pathophysiology of TSC, review its clinical manifestations, and explore the breadth of imaging features in each organ system, from prenatal detection of cardiac rhabdomyomas to monitoring rapamycin therapy to treatment of AMLs by interventional radiology.

Uterine PEComa: appraisal of a controversial and increasingly reported mesenchymal neoplasm

In recent years, a group of tumors that have been designated "perivascular epithelioid cell tumors" (PEComa) have been reported with increasing frequency from a wide variety of anatomic locations. The uterus and retroperitoneum appear to be the most frequent sites of origin for these lesions. PEComas belong to an identically named family of tumors comprised of conventional angiomyolipomas, clear cell sugar tumors, lymphangiomyomatosis and clear cell myomelanocytic tumor of the falciform ligament/ligament teres, and are also known as PEComa-NOS. This article is a primer for clinicians on the most salient clinicopathologic features of uterine PEComas, as most of the debate and discussion have taken place in the pathologic literature. The author appraises in detail the current state of knowledge on PEComas of the uterus based on a review of published data on the 44 previously reported cases, and comments on areas of controversy. The latter are centered predominantly on the significant morphologic and immunophenotypic overlap that exists between uterine PEComa and some smooth muscle tumors of the uterus. The clinicopathologic features of cases reported as epithelioid smooth muscle tumors and cases reported as uterine PEComas are compared and contrasted, and a practical approach to their reporting is proposed.