Prognostic stratification of clinical and molecular epithelioid hemangioendothelioma subsets

Subclavian vein epithelioid hemangioendothelioma: Multidisciplinary surgical approach

Epithelioid hemangioendothelioma (EHE) is a rare primary vascular tumour, usually malignant. We present the case of a 60-year-old woman who presented with hoarseness of voice and a persistent cough. During evaluation, a left supraclavicular mass was discovered. Initial assessments revealed a 30-mm left supraclavicular mass. Computed tomography angiogram and venogram confirmed an enhancing mass arising directly from the proximal left subclavian vein. After discussion in the joint multidisciplinary team, it was decided to resect the tumour owing to its malignant potential. Histopathology after resection confirmed a completely excised EHE. EHE is a rare vascular sarcoma requiring a multidisciplinary approach. Its main challenge is its unpredictable behaviour.

Proposed diagnostic and prognostic markers of primary malignant hepatic vascular neoplasms

INTRODUCTION

Primary malignant hepatic vascular tumors with various malignant potentials include epithelioid hemangioendothelioma (EHE) and angiosarcoma (AS), which may overlap pathologically. This study aimed to compare the pathological findings of hepatic EHE with those of AS, in association with patient outcomes.

METHODS

Fifty-nine histologically confirmed patients with 34 EHE and 25 AS were admitted to a tertiary hospital from 2003 to 2020. Their EHE and AS pathological features were compared. Immunohistochemistry for CD31, ERG, CAMTA-1, TFE3, P53, and Ki-67 labeling was performed on paraffin-embedded blocks. Markers, along with histological findings, were analyzed for the purposes of diagnostic and prognostic significance by multivariate analysis.

RESULTS

CAMTA-1 was 91.2% positive in EHE, but negative in AS (p = < 0.001). AS was significantly correlated to an aberrant p53 expression, high Ki-67 labeling, and high mitotic activity, compared to EHE (all, p = < 0.001). EHE can be classified as low grade (LG) and high grade (HG) using the prognostic values of mitotic activity and ki-67 labeling (sensitivity = 1, specificity = 1). Low grade-EHE showed significantly better overall survival than high grade-EHE (p = 0.020).

CONCLUSIONS

Immunohistochemistry for CAMTA-1, P53, and Ki-67 labeling may help distinguish EHE and AS in histologically ambiguous cases, especially small biopsied tissue. Moreover, the combination of mitotic activity and Ki-67 labeling can be a prognostic factor for EHE with various clinical features.

Neurosurgical Management of Spinal Epithelioid Hemangioendothelioma: Systematic Review and Illustrative Case Presentation

BACKGROUND

Epithelioid hemangioendothelioma (EHE) is a rare vascular tumor predominantly arising in soft tissue. We report a rare case of thoracic spinal EHE with pulmonary metastasis.

METHODS

Case report and systematic review of spinal EHE.

RESULTS

A 36-year-old man presented with bilateral lower extremity weakness, progressive paresthesia, and urinary incontinence. He underwent open surgical resection of the tumor and decompression of the spinal cord, with subsequent improvement in neurologic function. Systematic review identified 84 cases of spinal EHE, 73 of which were primary, and 14 of which developed extra-spinal metastases.

CONCLUSION

EHE is an exceedingly rare tumor that may present with a wide swath of clinical symptoms. At present, no guidelines or formal treatment recommendations have been established. Surgical debulking has demonstrated efficacy as a front-line treatment, particularly in the setting of compressive neurologic dysfunction; data regarding adjuvant chemoradiation are less consistently reported, mandating further study.

Vascular tumors of intermediate malignancy: An update

The term "hemangioendothelioma" is used for endothelial neoplasms of intermediate malignancy and describes a group of rare neoplasms having biologic behavior falling in between that of the benign hemangiomas and fully malignant angiosarcomas. The hemangioendotheliomas fall into several specific, clinicopathologically and genetically distinct entities, specifically epithelioid hemangioendothelioma, kaposiform hemangioendothelioma, papillary intralymphatic angioendothelioma and retiform hemangioendothelioma (hobnailed hemangioendothelioma), pseudomyogenic hemangioendothelioma, composite hemangioendothelioma, and YAP1::TFE3-fused hemangioendothelioma. The clinical, morphologic, immunohistochemical, and genetic features, and the differential diagnosis of each of these rare entities are discussed in this review.

How Molecular Discoveries Have Changed Liver Tumor Pathology: A Brief Review

CONTEXT

Recent molecular discoveries have led to improved understanding of tumor biology and the development of new diagnostic assays.

OBJECTIVE

To review primarily 3 examples of liver tumors and to briefly illustrate how recent molecular discoveries have altered clinical liver pathology practice.

DATA SOURCES

First, we will discuss fibrolamellar carcinoma, which will be the main focus of discussion, as an example for new diagnostic tests that have been developed as a result of molecular discoveries. Additional information on the role of molecular diagnostics in hepatocellular adenoma and hepatocellular carcinoma will be provided. Second, we will use the example of epithelioid hemangioendothelioma as an example of how new diagnostic tools, based on molecular discoveries, may support improved prognostication. Finally, we will use the example of intrahepatic cholangiocarcinoma as an example of a liver tumor where new molecular discoveries have identified tractable therapeutic targets and led to new effective therapies. This portion of the manuscript will also include a description of the anatomic and molecular differences between intrahepatic, hilar, and extrahepatic cholangiocarcinoma.

CONCLUSIONS

Fueled by molecular discoveries, new and better diagnostic tests and therapeutic targets have improved clinical care in patients affected by liver tumors.

A case report of parotid gland epithelioid hemangioendothelioma

Epithelioid hemangioendothelioma (EHE) is a rare low-grade malignant vascular tumor. It mainly occurs in the liver, lungs, bones, and other parts of the body. Reports of epithelioid hemangioendothelioma in the parotid gland are rare in both domestic and international literature. Here, we present a case report of a parotid gland epithelioid hemangioendothelioma, including its complete clinical course and imaging findings, to improve the diagnosis and treatment of this unusual disease.

Case presentation

The patient, a 75-year-old female, presented with a swelling around the right ear for 2 months and pain for 20 days. Enhanced MRI of the parotid gland revealed a well-defined, round mass with homogeneous signal intensity. The mass showed low signal intensity on T1-weighted imaging, high signal intensity on T2-weighted imaging, nodular low signal intensity within, significant high signal intensity on DWI sequence, low signal intensity on ADC sequence, and heterogeneous enhancement in the arterial phase after intravenous injection of Gd-DTPA. Nodular non-enhancing low signal intensity was observed internally, and slight clearance was seen in the venous phase. The initial diagnosis before surgery was a benign lesion, but after histopathological and immunohistochemical examination, it was confirmed as epithelioid hemangioendothelioma.

Intervention

Complete tumor resection was performed.

Results

The patient experienced a favorable recovery, with meticulous follow-up conducted for up to 1 year revealing no signs of recurrence or metastasis. Continued patient surveillance is ongoing to substantiate and validate the long-term efficacy of the treatment.

Conclusion

Due to the extreme rarity of parotid gland epithelioid hemangioendothelioma, it often leads to a high misdiagnosis rate. The most common misdiagnosis is salivary gland lymphoma, followed by epithelioid hemangiosarcoma. When the lesion is multifocal, fusiform, with internal necrosis, and shows punctate low signal intensity on T2-weighted imaging, significant enhancement in the arterial phase, particularly with more pronounced peripheral enhancement, and persistent enhancement in the venous and delayed phases, epithelioid hemangioendothelioma should be considered. However, the current clinical diagnosis of epithelioid hemangioendothelioma still primarily relies on immunohistochemical methods.

Vascular Neoplasms With NFATC1/C2 Gene Alterations : Expanding the Clinicopathologic and Molecular Characteristics of a Distinct Entity

Despite significant advances in their molecular pathogenesis, skeletal vascular tumors remain diagnostically challenging due to their aggressive radiologic appearance and significant morphologic overlap. Within the epithelioid category and at the benign end of the spectrum, recurrent FOS/FOSB fusions have defined most epithelioid hemangiomas, distinguishing them from epithelioid hemangioendothelioma and angiosarcoma. More recently, the presence of EWSR1/FUS :: NFATC1/2 fusions emerged as the genetic hallmark of a novel group of unusual vascular proliferations, often displaying epithelioid morphology, with alternating vasoformative and solid growth, variable atypia, reminiscent of composite hemangioendothelioma. In this study, we further our understanding and morphologic spectrum of NFATC -fusion positive vascular neoplasms by describing 9 new cases, including soft tissue locations and novel fusion partners. Combining with the initial cohort of 5 cases, a total of 14 patients were analyzed, showing slight female predilection and an age range of 10 to 66 (mean 42 y). Twelve patients had solitary lesions, while 2 had multifocal polyostotic (pelvic bones) disease. Overall, 12 lesions were intra-osseous and 2 in soft tissue. By targeted RNA Fusion panels or FISH, there were 6 cases of EWSR1::NFATC1 , 4 EWSR1::NFATC2 , 2 FUS::NFATC2 , 1 EWSR1 rearrangement, and 1 with a novel FABP4::NFATC2 fusion. Follow-up was available in 4 patients. One patient experienced 2 local recurrences, 11 and 15 years postdiagnosis, and one patient experienced progressive disease despite multimodality treatment (curettings, embolization, radiation) over 3 years. In summary, our extended investigation confirms that NFATC -related fusions define a distinct group of vascular neoplasms with variable architecture, epithelioid phenotype, and cytologic atypia, commonly located in the bone, occasionally multifocal and with potential for local recurrence and aggressive behavior but no metastatic potential. Molecular analysis is recommended in diagnostically challenging cases with atypical histology to exclude malignancy.

Epithelioid hemangioendothelioma-its history, clinical features, molecular biology and current therapy

Epithelioid hemangioendothelioma (EHE) is a remarkably rare tumor arising from endothelial cells that is classified as a vascular tumor in the WHO classification. The tumor is predominantly characterized by the presence of fusion genes, such as WWTR1-CAMTA1 or YAP1-TFE3, with a minority of cases exhibiting other rare fusion genes. EHE exhibits a broad age of onset, typically presenting at ~50 years, but it is not uncommon in pediatric populations. It manifests in a variety of organs, including the liver, lung, soft tissue and bone. Initial multiple-organ involvement is also observed. The tumor's biological behavior and prognosis vary substantially based on the primary site of manifestation. From a therapeutic perspective, initial active surveillance might be considered in selected cases, although surgical intervention remains the mainstay of treatment, especially for localized single-organ involvement. Chemotherapy is administered to patients with progressive unresectable tumors. Recent advances in the biological analysis of EHE fusion genes have elucidated their diverse functions. Additionally, next-generation sequencing has facilitated the identification of other mutations beyond the fusion genes. These continuous efforts to understand the biology of the fusion genes themselves and/or the dysregulated signaling by fusion genes are expected to lead to the development of novel therapeutic strategies for EHE. This article aims to provide a comprehensive review of EHE, encompassing its historical context, clinical manifestations, molecular biology and the current state of treatment.

Multifocal lower limb hemangioendothelioma in a young female: a case report and review of the literature

A 26-year-old female presented with pain and swelling of distal thigh and distal leg. She was diagnosed with multifocal epitheloid hemangioendothelioma (EHE) and was successfully treated with wide resection of femoral and tibial lesions followed by their reconstruction using vascularised fibular graft and local bone grafting. One year into follow-up, the patient remained asymptomatic with full Range Of Motion (ROM) and full weight bearing walking. This case illustrates a unique multifocal presentation of hemangioendothelioma and early surgical intervention leading to complete recovery, highlighting the importance of early diagnosis and intervention to help improve prognosis and quality of life of the patient.

The patient perspective on sirolimus for epithelioid hemangioendothelioma (EHE): results of a community survey highlighting the importance of equitable access to treatments

Background

Epithelioid hemangioendothelioma (EHE) is an ultra-rare, vascular sarcoma with clinical presentation ranging from an indolent to an aggressive form. Over 50% of patients present with metastatic disease, requiring systemic therapy, although no systemic therapies are specifically approved for EHE. Retrospective evidence supports the activity of mTOR inhibitors (e.g. sirolimus), although available only off-label. EHE patients and advocates are therefore working to support approval of effective treatments by collecting data on patient perspectives and experiences.

Materials and methods

In February 2023, the EHE Rare Cancer Charity (UK) and The EHE Foundation (US), with other advocates, conducted a survey of perspectives and experiences of EHE patients regarding the use and accessibility of sirolimus. The survey consisted of 20 questions designed for individuals undergoing treatment, those who had been treated, or had never been treated with the drug. Widely promoted within the patient community, the online survey categorized patients into three cohorts for the analysis: liver transplant patients, non-transplant patients who had ever taken sirolimus and sirolimus-naïve non-transplant patients.

Results

The survey evaluated data from 129 patient responses from 21 countries, mostly from USA, UK, Australia, and Canada (70%). The liver transplant, sirolimus and non-sirolimus cohorts were 16%, 25% and 59%, respectively. In the sirolimus group 66% reported treatment durations exceeding one year, with 16% exceeding five years, indicating the drug's efficacy. In the non-sirolimus group, the drug was not available for 42% and for 11% sirolimus was available but not selected for treatment because of its off-label status. Overall, 87% of all patients across all cohorts expressed the importance of the drug's availability as hugely or very important.

Conclusion

The survey responses highlight the activity of sirolimus for EHE and the importance of securing a label extension for the drug delivering equitable access to this treatment for patients.

Epithelioid hemangioendothelioma (EHE) with WWTR1::TFE3 gene fusion, a novel fusion variant

Epithelioid hemangioendothelioma (EHE) is a rare endothelial sarcoma associated with a high incidence of metastases and for which there are no standard treatment options. Based on disease-defining mutations, most EHEs are classified into two subtypes: WWTR1::CAMTA1-fused EHE or YAP1::TFE3-fused EHE. However, rare non-canonical fusions have been identified in clinical samples of EHE cases and are challenging to classify. In this study, we report the identification of a novel WWTR1::TFE3 fusion variant in an EHE patient using targeted RNA sequencing. Histologically, the tumor exhibited hybrid morphological characteristics between WWTR1::CAMTA1-fused EHE and YAP1::TFE3-fused EHE. In addition to the driver fusion, there were six additional secondary mutations identified, including a loss-of-function FANCA mutation. Furthermore, in vitro studies were conducted to investigate the tumorigenic function of the WWTR1::TFE3 fusion protein in NIH3T3 cells and demonstrated that WWTR1::TFE3 promotes colony formation in soft agar. Finally, as the wild-type WWTR1 protein relies on binding the TEAD family of transcription factors to affect gene transcription, mutation of the WWTR1 domain of the fusion protein to inhibit such binding abrogates the transformative effect of WWTR1::TFE3. Overall, we describe a novel gene fusion in EHE with a hybrid histological appearance between the two major genetic subtypes of EHE. Further cases of this very rare subtype of EHE will need to be identified to fully elucidate the clinical and pathological characteristics of this unusual subtype of EHE.

Short-term outcomes of combined therapy with sirolimus and interferon-alpha 2b for advanced hepatic epithelioid hemangioendothelioma

Background

Hepatic epithelioid hemangioendothelioma (EHE) is an extremely rare tumor, and no standard therapy has been established yet.

Objectives

The aim of this study was to investigate the short-term results of combined therapy with sirolimus and interferon-alpha 2b (IFN-a 2b) (SI therapy).

Methods

From January 2022 to April 2023, 40 patients histologically diagnosed with hepatic EHE and progressive disease received SI therapy. All patients were regularly evaluated for the safety and efficacy of the SI therapy. Patients who received SI therapy for <3 months without a tumor status evaluation after treatment were excluded.

Results

Twenty-nine patients with hepatic EHE were included in this study. The Eastern Cooperative Oncology Group (ECOG) performance status was 0 in 19 (65.5%) patients and 1 in 10 (34.5%) patients. The median duration of the SI therapy was 8 months (range, 3-15 months). Twenty-three (79.3%) patients showed a decrease in tumor size, including 11 (37.9%) patients who achieved a partial response and one (3.4%) who achieved a complete response; the objective response rate was 41.4%. Stable disease was observed in 13 (44.8%) patients, with a disease control rate of 86.2%. Adverse events (AES) were observed in 18 patients, including leukopenia (31.0%), oral ulcers (13.8%), and liver injury (10.3%). No severe (grade ⩾ 3) AEs were recorded, and SI therapy was not interrupted for any patient due to AEs.

Conclusion

Sirolimus and IFN-a 2b may have synergistic effects in the treatment of hepatic EHE. SI therapy is a safe and effective treatment for hepatic EHE patients with good ECOG performance status.

Mesenchymal tumours of the pleura: review and update

Primary mesenchymal tumours of the pleura are uncommon and can be diagnostically challenging due to their overlapping histopathologic and immunophenotypic features. Herein we discuss selected mesenchymal tumours of the pleura, including solitary fibrous tumour, calcifying fibrous tumour, desmoid fibromatosis, synovial sarcoma, schwannoma, malignant peripheral nerve sheath tumour, inflammatory myofibroblastic tumour, follicular dendritic cell sarcoma, epithelioid hemangioendothelioma, and desmoplastic small round cell tumour. We review their clinicopathologic characteristics, along with an update on the relevant immunohistochemical and molecular features.

Soft tissue epithelioid hemangioendothelioma on the palm of the hand. Case report

Hemangioendothelioma is a malignant vascular tumor, according to ISSVA classification of vascular tumors. This patient presented an epithelioid hemangioendothelioma; this type of tumor can exhibit significant local destruction, sometimes requiring limb amputation. With deferred Mohs micrographic surgery and reconstructive surgery with multiple conventional and microsurgical techniques, partial or total amputation of the hand was avoided.

A Matched Molecular and Clinical Analysis of the Epithelioid Haemangioendothelioma Cohort in the Stafford Fox Rare Cancer Program and Contextual Literature Review

BACKGROUND

Epithelioid haemangioendothelioma (EHE) is an ultra-rare malignant vascular tumour with a prevalence of 1 per 1,000,000. It is typically molecularly characterised by a WWTR1::CAMTA1 gene fusion in approximately 90% of cases, or a YAP1::TFE3 gene fusion in approximately 10% of cases. EHE cases are typically refractory to therapies, and no anticancer agents are reimbursed for EHE in Australia.

METHODS

We report a cohort of nine EHE cases with comprehensive histologic and molecular profiling from the Walter and Eliza Hall Institute of Medical Research Stafford Fox Rare Cancer Program (WEHI-SFRCP) collated via nation-wide referral to the Australian Rare Cancer (ARC) Portal. The diagnoses of EHE were confirmed by histopathological and immunohistochemical (IHC) examination. Molecular profiling was performed using the TruSight Oncology 500 assay, the TruSight RNA fusion panel, whole genome sequencing (WGS), or whole exome sequencing (WES).

RESULTS

Molecular analysis of RNA, DNA or both was possible in seven of nine cases. The WWTR1::CAMTA1 fusion was identified in five cases. The YAP1::TFE3 fusion was identified in one case, demonstrating unique morphology compared to cases with the more common WWTR1::CAMTA1 fusion. All tumours expressed typical endothelial markers CD31, ERG, and CD34 and were negative for pan-cytokeratin. Cases with a WWTR1::CAMTA1 fusion displayed high expression of CAMTA1 and the single case with a YAP1::TFE3 fusion displayed high expression of TFE3. Survival was highly variable and unrelated to molecular profile.

CONCLUSIONS

This cohort of EHE cases provides molecular and histopathological characterisation and matching clinical information that emphasises the molecular patterns and variable clinical outcomes and adds to our knowledge of this ultra-rare cancer. Such information from multiple studies will advance our understanding, potentially improving treatment options.

Mesenchymal Neoplasms of the Liver

Mesenchymal neoplasms of the liver can be diagnostically challenging, particularly on core needle biopsies. Here, I discuss recent updates in neoplasms that are specific to the liver (mesenchymal hamartoma, undifferentiated embryonal sarcoma, calcifying nested stromal-epithelial tumor), vascular tumors of the liver (anastomosing hemangioma, hepatic small vessel neoplasm, epithelioid hemangioendothelioma, angiosarcoma), and other tumor types that can occur primarily in the liver (PEComa/angiomyolipoma, inflammatory pseudotumor-like follicular dendritic cell sarcoma, EBV-associated smooth muscle tumor, inflammatory myofibroblastic tumor, malignant rhabdoid tumor). Lastly, I discuss metastatic sarcomas to the liver, as well as pitfalls presented by metastatic melanoma and sarcomatoid carcinoma.

NOTCH3 missense mutations as predictor of long-term response to gemcitabine in a patient with epithelioid hemangioendothelioma

PURPOSE

Epithelioid hemangioendothelioma (EHE) as a very rare malignant vascular tumor belongs to the heterogenous group of soft-tissue sarcomas. Depending on the clinical course of the disease, interdisciplinary treatment concepts are required, including surgery, radiotherapy and systemic cancer therapy. However, due to its uncommonness, standard treatment options are lacking so far, especially in advanced disease with distant metastases.

METHODS AND RESULTS

Here we report on an unusual case of a patient with metastasized EHE showing long-term response to second line treatment with gemcitabine over almost 2 decades. Cancer genome sequencing of the patient's tumor tissue detected a NOTCH3 missense mutation which could provide an explanation for these clinical findings. NOTCH3 is known to be a mediator of resistance towards gemcitabine-based cancer treatment, at least in pancreatic cancer and non-small cell lung cancer.

CONCLUSION

The observation that this missense mutation of NOTCH3 is associated with an increased response to treatment with gemcitabine in EHE can be used prospectively to assess NOTCH3 as potential biomarker for predicting therapy response to gemcitabine.

Incidence, demographics, and survival of malignant hemangioendothelioma in the United States

BACKGROUND

Malignant hemangioendothelioma is an endothelial cancer with heterogeneous clinical behavior that can range from indolent to aggressive, of which the majority are epithelioid (EHE). Its incidence and demographics have not been previously well defined in a large cohort.

METHODS

This retrospective analysis used the US Cancer Statistics National Program of Cancer Registries - Surveillance Epidemiology End Results (SEER) combined database to identify patients in the US newly diagnosed with hemangioendothelioma between the years of 2001 and 2017 (n = 1986). Survival analyses were performed on a subset of patients within the SEER-18 database with survival information available (n = 417). Outcomes included incidence, demographics of patients newly diagnosed with hemangioendothelioma, extent of disease at presentation, and overall survival.

RESULTS

The incidence of hemangioendothelioma in the US is 0.4 cases per million person-years. Although cases rose to 122 newly diagnosed in the year 2017 (90 EHE, 32 other hemangioendothelioma), incidence rates were stable. Skin and connective tissues were the most common presenting sites (33.4%), followed by liver (24.5%), lung (17.6%), and bone (12.5%). Median age at diagnosis was 55 years; 27.2% of patients were pediatric, adolescent, or young adult (<40 years). At presentation, 36.4% of patients had localized disease; 21.6% presented with regional and 41.7% with distant metastases. Observed survival at 3 years was 79.7%, 70.7%, and 46.0% for patients presenting with local, regional, and distant disease and most deaths occurred within the first 2 years.

CONCLUSIONS

Malignant hemangioendothelioma is ultra-rare but meaningfully impacts affected patients. These data may provide benchmarks for comparison of new approaches to hemangioendothelioma therapy and highlight poor survival outcomes.

Prognostic Factors in Epithelioid Hemangioendothelioma: Analysis of a Nationwide Molecularly/Immunohistochemically Confirmed Cohort of 57 Cases

Epithelioid hemangioendothelioma (EHE) is an extremely rare vascular sarcoma with variable aggressive clinical behavior. In this retrospective study, we aimed to investigate prognostic factors based on clinicopathologic findings in a molecularly/immunohistochemically confirmed nationwide multicenter cohort of 57 EHE cases. Patients had unifocal disease (n = 29), multifocal disease (n = 5), lymph node metastasis (n = 8) and/or distant metastasis (n = 15) at the time of diagnosis. The overall survival rate was 71.4% at 1 year and 50.7% at 5 years. Survival did not correlate with sex, age or histopathological parameters. No survival differences were observed between multifocal and metastatic disease, suggesting that multifocality represents early metastases and treatment options are limited in comparison to unifocal disease. In unifocal tumors, survival could be predicted using the risk stratification model of Shibayama et al., dividing the cases into low- (n = 4), intermediate- (n = 15) and high- (n = 3) risk groups. No clinical or histopathological parameters were associated with progressive unifocal disease course. Lymph node metastases at the time of diagnosis occurred in 14.0% of the cases and were mainly associated with tumor localization in the head and neck area, proposing lymph node dissection. In conclusion, our results demonstrate the aggressive behavior of EHE, emphasize the prognostic value of a previously described risk stratification model and may provide new insights regarding tumor focality, therapeutic strategies and prognosis.

Current Model Systems for Investigating Epithelioid Haemangioendothelioma

Epithelioid haemangioendothelioma (EHE) is a rare sarcoma of the vascular endothelium with an unpredictable disease course. EHE tumours can remain indolent for long period of time but may suddenly evolve into an aggressive disease with widespread metastases and a poor prognosis. Two mutually exclusive chromosomal translocations define EHE tumours, each involving one of the transcription co-factors TAZ and YAP. The TAZ-CAMTA1 fusion protein results from a t(1;3) translocation and is present in 90% of EHE tumours. The remaining 10% of EHE cases harbour a t(X;11) translocation, resulting in the YAP1-TFE3 (YT) fusion protein. Until recently, the lack of representative EHE models made it challenging to study the mechanisms by which these fusion proteins promote tumorigenesis. Here, we describe and compare the recently developed experimental approaches that are currently available for studying this cancer. After summarising the key findings obtained with each experimental approach, we discuss the advantages and limitations of these different model systems. Our survey of the current literature shows how each experimental approach can be utilised in different ways to improve our understanding of EHE initiation and progression. Ultimately, this should lead to better treatment options for patients.

Application of immunohistochemical studies in diagnosing emerging superficial mesenchymal neoplasms

Molecular diagnostics, with the subsequent development of novel immunohistochemical markers, continues to advance and expand the field of soft tissue pathology. As such, the ever-evolving molecular diagnostic landscape will continue to shape and refine our understanding and classification of neoplasms. This article reviews the current literature on various tumors of mesenchymal origin, including fibroblastic/fibrohistiocytic, adipocytic, vascular, and tumors of uncertain origin. We aim to give the reader a detailed understanding and pragmatic approach to various new and established immunohistochemical stains in diagnosing these neoplasms and also discuss various pitfalls with significant repercussions.

Case report: Surgical treatment of a primary giant epithelioid hemangioendothelioma of the spine with total en-bloc spondylectomy

Background

Epithelioid hemangioendothelioma (EHE) is an extremely uncommon malignant neoplasm that originates from vascular endothelial or pre-endothelial cells. In this report, we present the case of patient who was diagnosed with a primary giant EHE of the spine and underwent treatment with total en-bloc spondylectomy (TES).

Case presentation

A 43-year-old male patient with a history of he presented to our hospital with chronic and progressive back pain. Physical examination revealed weakened sensation of acupuncture and touch on the left costal arch, while relatively normal neurological functions were preserved. Radiological examinations identified a giant destructive soft tissue lesion occupying the T8 vertebral region, with moderate destruction of the pedicle and lamina, as well as the 7th left rib. A preoperative biopsy of the 8th vertebra resulted in a diagnosis of epithelioid hemangioendothelioma(EHE). Postoperative immunohistochemical and pathological reports confirmed the presence of EHE in the left ribs and T8 ribs. The patient underwent resection of the 7th left rib and posterior pedicle screw fixation with 8 pairs of screws and a titanium mesh cage. Subsequently, thoracic en bloc spondylectomy was performed on the T8 vertebra. The patient did not receive radiation or chemotherapy following surgery. Over a period of 3 years, the patient remained free of disease and relapse.

Conclusion

The use of transarterial embolization with spherical embolic agents (TES) has been demonstrated to be a safe, effective, and reliable treatment option for hepatic epithelioid hemangioendothelioma (EHE). Nevertheless, it is crucial to conduct long-term follow-up of this patient in order to assess their clinical outcome.

Diagnosis, Management, and Prognosis of Epithelioid Hemangioendothelioma of Maxillary Sinus: A Case Report

Epithelioid hemangioendothelioma (EHE) is a rare condition arising from endothelial cells of the blood vessels. This is a vascular tumor that may occur anywhere throughout the body. This tumor behaves on a spectrum as either a benign tumor or an aggressive sarcoma. The EHE tumor and its management depend on the location of the lesion and accessibility for surgical excision. This case is a rare example of a patient presenting with a maxillary aggressive EHE tumor. This lesion was incidentally found on head CT done for ruling out fractures of the mid-face with incidental findings of an asymptomatic destructive lytic lesion. The treatment of this tumor located in a vital region of the mid-face will be discussed.

Poor response to sintilimab plus chemotherapy in a pulmonary epithelioid hemangioendothelioma patient: a case report

Pulmonary epithelioid hemangioendothelioma (PEH) is a rare vascular tumor with no established treatment protocol. The authors report the case of a young woman diagnosed with PEH. DNA and RNA analysis by next-generation sequencing was performed on the tumor tissue. A novel germline PALB2 mutation and classical WWTR1-CAMTA1 fusion were identified. She experienced a poor response to sintilimab (a PD-1 inhibitor) plus platinum-based chemotherapy as the first-line treatment. PEH patients harboring a germline PALB2 mutation and WWTR1-CAMTA1 gene fusion may respond poorly to treatment with PD-1 inhibitors plus chemotherapy.

Hepatic epithelioid hemangioendothelioma: how fast does it grow and which findings could have prevented diagnostic delay?-a case report

Background

Hepatic epithelioid hemangioendothelioma (HEHE) is a rare neoplastic disease of varied presentation and unspecific radiological signs in the early stages. The diagnostic delay can lead to metastatic disease, thus increasing the tumor burden and reducing the treatment options. HEHE is usually deemed a slow-growing tumor, but its speed of growth is poorly reported and still unknown.

Case Description

In this case report, we documented a HEHE diagnosed in a young woman who had complaints of abdominal pain, weight loss and bloating for a long time. The typical findings observed in histological studies were not promptly recognized in the histological analyzes, even after two laparoscopic-guided liver biopsies, delaying the diagnosis until extrahepatic tumor spreading. Findings observed in computed tomography, magnetic resonance imaging and histological studies are presented. The coalescence of nodules and the rising of giant masses, occupying large parts of the liver in a specific time span, were registered and quantified. As opposed to prior reports, the results show that hepatic HEHE can grow rapidly, reinforcing the need of early diagnosis, thus avoiding the complications presented herein.

Conclusions

The findings observed via radiological and histological imaging that could have avoided the diagnosis delay are depicted and discussed, showing that HEHE can rise faster than previously documented.

Epithelioid Hemangioendothelioma of the Liver Showing Spontaneous Complete Regression after the Cessation of Methotrexate Intake

A 71-year-old man with slight fever and dull abdominal pain was referred to our hospital. He had been receiving methotrexate (MTX) to treat his rheumatoid arthritis for more than 6 years but stopped taking MTX after admission due to the rapid aggravation of his liver function. Computed tomography (CT) showed multiple liver lesions with late enhancement, highly suggesting them to be cholangiocarcinomas. Tumor marker levels were normal except for a slightly elevated PIVKA-II level, i.e., 45 mAU/mL (range 0-40 mAU/mL). We did a biopsy to the largest lesion and endoscopic biliary drainage to make a definitive diagnosis of the hepatic lesions and treat jaundice, respectively. Pathological study showed round, polygonal, and spindle-shaped epithelial atypical cells growing in a sarcomatoid fashion. Atypical cells were positive for CD31, CD34, vimentin, and TFE3, and some of them had intracellular vacuoles, leading to the diagnosis of epithelioid hemangioendothelioma (EHE) of the liver. The patient got well 4 weeks after the endoscopic biliary drainage. CTs showed marked regression of the EHE lesions 3 months after biliary drainage and complete regression in 12 months. The patient further developed Hodgkin lymphoma in the para-aortic lymph nodes 23 months after the biliary drainage and is now under chemotherapy for the malignant lymphoma. We, however, have not detected any EHE lesions in the liver or distant organs for at least 16 months after the confirmation of complete regression of the EHE lesions. Oncologists should note the spontaneous regression of the EHE and investigate the correlation between MTX cessation and EHE regression.

Epithelioid hemangioendothelioma of the distal lower extremity and the role of radiotherapy: A report of two cases

We report two cases of epithelioid hemangioendothelioma (EHE) in the distal lower extremity. Our first patient had unicentric EHE of the left os calcis initially treated with an intralesional procedure; however, later developed two recurrences which were managed with radiation therapy. Our second patient had multicentric EHE of the distal tibia and fibula managed with primary radiation therapy. Although EHE is typically treated with wide resection or an intralesional procedure, we present two cases of EHE in the distal lower extremity to discuss the therapeutic role of radiation therapy in the management of distal EHE.

Molecular testing of soft tissue tumors

BACKGROUND

The diagnosis of soft tissue tumors is challenging, especially when the evaluable material procured is limited. As a result, diagnostic ancillary testing is frequently needed. Moreover, there is a trend in soft tissue pathology toward increasing use of molecular results for tumor classification and prognostication. Hence, diagnosing newer tumor entities such as CIC-rearranged sarcoma explicitly requires molecular testing. Molecular testing can be accomplished by in situ hybridization, polymerase chain reaction, as well as next generation sequencing, and more recently such testing can even be accomplished leveraging an immunohistochemical proxy.

CONCLUSION

This review evaluates the role of different molecular tests in characterizing soft tissue tumors belonging to various cytomorphologic categories that have been sampled by small biopsy and cytologic techniques.

Genetic Alterations and Deregulation of Hippo Pathway as a Pathogenetic Mechanism in Bone and Soft Tissue Sarcoma

The Hippo pathway is an evolutionarily conserved modulator of developmental biology with a key role in tissue and organ size regulation under homeostatic conditions. Like other signaling pathways with a significant role in embryonic development, the deregulation of Hippo signaling contributes to oncogenesis. Central to the Hippo pathway is a conserved cascade of adaptor proteins and inhibitory kinases that converge and regulate the activity of the oncoproteins YAP and TAZ, the final transducers of the pathway. Elevated levels and aberrant activation of YAP and TAZ have been described in many cancers. Though most of the studies describe their pervasive activation in epithelial neoplasms, there is increasing evidence pointing out its relevance in mesenchymal malignancies as well. Interestingly, somatic or germline mutations in genes of the Hippo pathway are scarce compared to other signaling pathways that are frequently disrupted in cancer. However, in the case of sarcomas, several examples of genetic alteration of Hippo members, including gene fusions, have been described during the last few years. Here, we review the current knowledge of Hippo pathway implication in sarcoma, describing mechanistic hints recently reported in specific histological entities and how these alterations represent an opportunity for targeted therapy in this heterogeneous group of neoplasm.

Interventional Management of Portal Hypertension in Cancer Patients

PURPOSE OF REVIEW

To provide an overview of the classifications and clinical hallmarks of common cancer-related conditions that contribute to the high incidence of portal hypertension in this population and provide an update on currently available interventional radiology therapeutic approaches.

RECENT FINDINGS

In the last few decades, there have been significant advancements in understanding the pathophysiology of portal hypertension. This knowledge has led to the development of safer and more effective minimally invasive approaches. The main objective is to provide alternatives to prevent life-threatening complications from clinically significant portal hypertension and to allow the continuation of cancer treatment interventions that would otherwise be stopped. Clinicians involved in cancer care should be aware of risk factors, associated complications, and management of portal hypertension in cancer patients. Interventional radiology offers minimally invasive alternatives that play a central role in improving clinical outcomes and survival of these patients, allowing the continuation of cancer treatments.

[Epithelioid Hemangioendothelioma Presenting as a Right Paratracheal Mass: A Case Report]

Epithelioid hemangioendothelioma (EHE) is a low-grade malignant vascular neoplasm that can occur anywhere in the body. EHE has a low annual incidence (0.38/106) and prevalence (< 1/106), and primary mediastinal EHE is exceedingly rare. We report a case of EHE in a 53-year-old female which manifested as an incidentally discovered mass in the right paratracheal region. In this report, authors describe the pathological and radiological findings of primary mediastinal EHE invading the superior vena cava in the right paratracheal area.

Establishment and Validation of a Nomogram Prognostic Model for Epithelioid Hemangioendothelioma

Background. Epithelioid hemangioendothelioma (EHE) is an ultrarare vascular sarcoma. At present, the epidemiological and clinical characteristics and prognostic factors are still unclear. Our study attempted to describe clinical features, investigate the prognostic indicators, and establish the nomogram prediction model based on the Surveillance, Epidemiology, and End Results (SEER) database for EHE patients. Methods. The patients diagnosed with EHE from 1986 to 2018 were collected from the SEER database and were randomly divided into a training group and a validation group at a ratio of 7 : 3. The Cox proportional hazard models were used to determine the independent factors affecting prognosis and establish a nomogram prognostic model to predict the survival rates for patients with EHE. The accuracy and discriminative ability of the model were measured using the concordance index, receiver operating characteristic curves, and calibration curves. The clinical applicability and application value of the model were evaluated by decision curve analysis. Results. The overall age-adjusted incidence of EHE was 0.31 patients per 1,000,000 individuals, with a statistically significant difference per year. Overall survival at 1, 5, and 10 years for all patients was 76.5%, 57.4%, and 48.2%, respectively. Multivariate Cox regression analysis identified age, tumour stage, degree of tissue differentiation, surgical treatment, chemotherapy, and radiotherapy as independent factors affecting prognosis ( $P<0.05$ ). The C-index values for our nomogram model of training group and validation group were 0.752 and 0.753, respectively. The calibration curve was in good agreement with the actual observation results, suggesting that the prediction model has good accuracy. The decision curve analysis indicated a relatively large net benefit. Conclusions. The nomogram model may play an important role in predicting the survival rate for EHE patients, with good concordance and accuracy, and can be applied in clinical practice.

Management of Vascular Sarcoma

Vascular sarcomas encompass 3 well-defined sarcoma types: hemangioendothelioma, Kaposi sarcoma, and angiosarcoma. These distinct types are exceedingly rare and very different in terms of clinical behavior, biological features, and treatment approach. Because of this rarity and heterogeneity, it is crucial that vascular sarcomas are treated in sarcoma reference centers or networks, in order to ensure optimal management. The diversity of vascular sarcomas also needs to be taken into account in the design of clinical trials, in order to produce meaningful results that can be consistently translated into everyday clinical practice.

Clear cell stromal tumor of the lung with YAP1::TFE3 fusion: four cases including case with highly aggressive clinical course

Clear cell stromal tumor of the lung (CCST-L) is a rare, recently recognized neoplasm, which has been found to express TFE3 and harbor YAP1::TFE3 fusions. Initial data suggested a benign process, however a single reported case gave rise to distant metastases. We sought to describe the clinicopathologic and molecular features of additional cases of CCST-L. Pathology and molecular archives were searched for cases of CCST-L or tumors with YAP1::TFE3 fusions. Clinical features were noted. Available slides, including immunohistochemical studies, were re-reviewed for diagnosis confirmation and assessment of pathologic features. Results of molecular studies were also recorded. Four tumors were identified, all occurring in women [median age 61 years (range: 24-69)]. Median tumor size was 4.4 cm (range: 1-9.5 cm); three tumors were unifocal and one was multifocal. Tumors were composed of epithelioid to spindled cells with eosinophilic to clear cytoplasm and grew in sheets, vague nests and short fascicles. Nuclear atypia was predominately mild, however two cases showed scattered atypical cells. Mitotic activity was generally low, though one case showed a mitotic count of 6/2 mm² . All tumors expressed TFE3 and harbored YAP1::TFE3 fusions. One case was unresectable and was treated with chemotherapy, and two underwent complete resection. One patient died of disease 7 months following diagnosis, while a second patient is alive with no evidence of disease after 43 months. Follow-up was not available for two cases. CCST-L expresses TFE3, harbors YAP1::TFE3 fusions and at least rare cases behave in an aggressive manner.

Unraveling the Biology of Epithelioid Hemangioendothelioma, a TAZ-CAMTA1 Fusion Driven Sarcoma

Simple Summary

Epithelioid hemangioendothelioma (EHE) is a rare vascular cancer that involves a gain-of-function gene fusion involving TAZ, a transcriptional coactivator, and one of two end effectors of the Hippo pathway. Although the activity of TAZ and/or YAP, a paralog of TAZ, is consistently altered in many cancers, genetic alterations involving YAP/TAZ are rare, and the precise mechanisms by which YAP/TAZ are activated are not well understood in most cancers. Because WWTR1(TAZ)–CAMTA1 is the only genetic alteration in approximately half of EHE, EHE is a genetically clean and homogenous system for understanding how the dysregulation of TAZ promotes tumorigenesis. Therefore, by using EHE as a model system, we hope to elucidate the essential biological pathways mediated by TAZ and identify mechanisms to target them. The findings of EHE research can be applied to other cancers that are addicted to high YAP/TAZ activity.

Abstract

The activities of YAP and TAZ, the end effectors of the Hippo pathway, are consistently altered in cancer, and this dysregulation drives aggressive tumor phenotypes. While the actions of these two proteins aid in tumorigenesis in the majority of cancers, the dysregulation of these proteins is rarely sufficient for initial tumor development. Herein, we present a unique TAZ-driven cancer, epithelioid hemangioendothelioma (EHE), which harbors a WWTR1(TAZ)–CAMTA1 gene fusion in at least 90% of cases. Recent investigations have elucidated the mechanisms by which YAP/TAP-fusion oncoproteins function and drive tumorigenesis. This review presents a critical evaluation of this recent work, with a particular focus on how the oncoproteins alter the normal activity of TAZ and YAP, and, concurrently, we generate a framework for how we can target the gene fusions in patients. Since EHE represents a paradigm of YAP/TAZ dysregulation in cancer, targeted therapies for EHE may also be effective against other YAP/TAZ-dependent cancers.

A review of neoplasms with MITF/MiT family translocations

Microphthalmia-associated transcription factor (MITF/MiT) family is a group of basic helix-loop-helix leucine zipper (bHLH-LZ) transcription factors including TFE3 (TFEA), TFEB, TFEC and MITF. The first renal neoplasms involving MITF family translocation were renal cell carcinomas with chromosome translocations involving ASPL-TFE3/t(X;17)(p11.23;q25) or MALAT1-TFEB/t(6;11)(p21.1;q12), and now it is known as MiT family translocation RCC in 2016 WHO classification. Translocations involving MITF family genes also are found in other tumor types, such as perivascular epithelioid cell neoplasm (PEComa), Alveolar soft part sarcoma (ASPS), epithelioid hemangioendothelioma, ossifying fibromyxoid tumor (OFMT), and clear cell tumor with melanocytic differentiation and ACTIN-MITF translocation. In this review, we summarize the features of different types of neoplasms with MITF family translocations.

The Hippo pathway in cancer: YAP/TAZ and TEAD as therapeutic targets in cancer

Tumorigenesis is a highly complex process, involving many interrelated and cross-acting signalling pathways. One such pathway that has garnered much attention in the field of cancer research over the last decade is the Hippo signalling pathway. Consisting of two antagonistic modules, the pathway plays an integral role in both tumour suppressive and oncogenic processes, generally via regulation of a diverse set of genes involved in a range of biological functions. This review discusses the history of the pathway within the context of cancer and explores some of the most recent discoveries as to how this critical transducer of cellular signalling can influence cancer progression. A special focus is on the various recent efforts to therapeutically target the key effectors of the pathway in both preclinical and clinical settings.

Primary Intranodal Epithelioid Hemangioendothelioma with Molecular Confirmation

Epithelioid hemangioendothelioma (EHE) is a rare low-grade malignant vascular tumor with indolent biology, characterized by reciprocal t(1;3)(p36.6;q25) with resultant WWTR1::CAMTA1 gene fusion in the vast majority of cases, regardless of anatomic location. Only a small subset, exhibiting well formed vasoformative features will contain YAP1::TFE3 gene fusion. Primary intranodal EHE is exquisitely rare. We report a case in a 54-year-old male with persistent left groin mass with discomfort for nine months. A CT of the abdomen and pelvis showed a minimally enlarged left inguinal lymph node measuring 2.8 cm with no other masses or lymphadenopathy. PET/CT and MRI imaging of the abdomen showed no evidence of disease elsewhere. Sections showed an epithelioid vasoformative neoplasm, centrally necrotic and involving a lymph node. The cells were arranged in anastomosing cords with intracytoplasmic lumens, resembling "signet ring cells". By immunohistochemistry, the tumor cells were positive for vimentin, CD31, CD34, ERG and CAMTA1; and negative for AE1/3, CAM 5.2, KRT7, KRT20, desmin, actin, HMB-45 and S-100. Ki-67 proliferation index was estimated at <1%. Molecular studies including next generation sequencing (NGS) revealed the presence of WWTR1::CAMTA1 gene fusion, and fluorescence in situ hybridization for CAMTA1 (1p36.23) and WWTR1 (3p25.1) showed fusion signals, diagnostic of EHE. We highlight a rare occurrence of EHE in a lymph node exhibiting morphologic mimicry with metastatic carcinoma.

Epithelioid hemangioendothelioma - an unexpected diagnosis of a mediastinal tumor with extensive local thrombosis

Epithelioid hemangioendothelioma (EHE) is a rare vascular tumor and the mediastinal localization is amongst the most infrequent. We present the case of a 37-year-old woman with a history of resected left thyroid tumor that presented to our department for evaluation of a left supraclavicular palpable mass in close contact with local vascular structures, and with heterogeneous contrast enhancement as described by computed tomography (CT) and magnetic resonance imaging (MRI). Considering the history of the patient, the presumptive diagnosis of thyroid tumor recurrence was established, and the patient was referred to surgical department. During procedure, we encountered important bleeding from a ruptured jugular vein branch, which we assumed to be a newly formed tumor blood vessel. After surgery (48 hours postoperatively), the patient developed important local thrombosis that encompassed the left internal jugular vein, left subclavian vein and the left brachiocephalic trunk that partially subsided after anticoagulant therapy. The histological examination revealed the presence of a vascular tumor proliferation of epithelioid endothelial cells that was characteristic of an EHE confirmed later on the immunohistochemical studies as Yes-associated protein 1-transcription factor E3 (YAP1-TFE3) subtype. In addition to the case report, some relevant information from the scarce literature data about mediastinal EHE were reviewed here.

The genetics of vascular tumours: an update

Recent molecular advances have shed significant light on the classification of vascular tumours. Except for haemangiomas, vascular lesions remain difficult to diagnose, owing to their rarity and overlapping clinical, radiographic and histological features across malignancies. In particular, challenges still remain in the differential diagnosis of epithelioid vascular tumours, including epithelioid haemangioma and epithelioid haemangioendothelioma at the benign/low-grade end of the spectrum, and epithelioid angiosarcoma at the high-grade end. Historically, the classification of vascular tumours has been heavily dependent on the clinical setting and histological features, as traditional immunohistochemical markers across the group have often been non-discriminatory. The increased application of next-generation sequencing in clinical practice, in particular targeted RNA sequencing (such as Archer, Illumina), has led to numerous novel discoveries, mainly recurrent gene fusions (e.g. those involving FOS, FOSB, YAP1, and WWTR1), which have resulted in refined tumour classification and improved diagnostic reproducibility for vascular tumours. However, other molecular alterations besides fusions have been discovered in vascular tumours, including somatic mutations (e.g. involving GNA family and IDH genes) in a variety of haemangiomas, as well as copy number alterations in high-grade angiosarcomas (e.g. MYC amplifications). Moreover, the translation of these novel molecular abnormalities into diagnostic ancillary markers, either fluorescence in-situ hybridisation probes or surrogate immunohistochemical markers (FOSB, CAMTA1, YAP1, and MYC), has been remarkable. This review will focus on the latest molecular discoveries covering both benign and malignant vascular tumours, and will provide practical diagnostic algorithms, highlighting frequently encountered pitfalls and challenges in the diagnosis of vascular lesions.

A YAP1::TFE3 cutaneous low-grade fibromyxoid neoplasm: A novel entity!

Cutaneous fibromyxoid neoplasms (CFMN) comprise a vast category of benign and malignant tumors that include, but are not limited to, low-grade fibromyxoid sarcoma, myxofibrosarcoma, myxoid dermatofibrosarcoma protuberans, myxoid solitary fibrous tumor, and myxoid neurofibroma with differing implications for treatment and prognosis. Herein, a case of CFMN arising as a painless, slow-growing, flesh-colored forearm mass in a 53-year-old female is presented. The neoplasm comprised of copious myxoid material with banal spindle cells, exhibiting mild hyperchromasia, dissecting the dermal collagen table. Focal perivascular accentuation of spindle cells was identified in the absence of vasoformative features. Immunohistochemically, lesional cells were strongly and diffusely positive for CD34 and multifocally for Factor XIIIa and epithelial membrane antigen while negative for CD31, ERG, FLI-1, D2-40, smooth muscle actin, Desmin, S100, HMB-45, STAT6, MUC4, and keratins. RNA- and DNA-sequencing identified a YAP1::TFE3 fusion transcript that were subsequently corroborated by fluorescence in situ hybridization and immunohistochemistry for TFE3 (Xp11.23) locus rearrangement and strong, diffuse TFE3 immunoreactivity, respectively. To date, the YAP1::TFE3 fusion has only been identified in a subset of epithelioid hemangioendotheliomas and clear cell stromal tumors of the lung. This is the first report of a CFMN featuring a YAP1::TFE3 fusion (YAP1 Exon 1 and TFE3 Exon 4). The morphologic findings are unlike those previously described for epithelioid hemangioendothelioma and suggest that this neoplasm may represent a yet unclassified or novel CFMN entity. Although the patient is 1-year status postsurgical excision with no evidence of clinical recurrence, the clinical behavior of this novel entity remains to be fully characterized.

YAP1-TFE3-fused hemangioendothelioma: a multi-institutional clinicopathologic study of 24 genetically-confirmed cases

YAP1-TFE3-fused hemangioendothelioma is an extremely rare malignant vascular tumor. We present the largest multi-institutional clinicopathologic study of YAP1-TFE3-fused hemangioendothelioma to date. The 24 cases of YAP1-TFE3-fused hemangioendothelioma showed a female predominance (17 female, 7 male) across a wide age range (20-78 years old, median 44). Tumors were most commonly located in soft tissue (50%), followed by bone (29%), lung (13%), and liver (8%), ranging from 3 to 115 mm in size (median 40 mm). About two-thirds presented with multifocal disease, including 7 cases with distant organ metastasis. Histopathologically, we describe three dominant architectural patterns: solid sheets of coalescing nests, pseudoalveolar and (pseudo)vasoformative pattern, and discohesive strands and clusters of cells set in a myxoid to myxohyaline stroma. These patterns were present in variable proportions across different tumors and often coexisted within the same tumor. The dominant cytomorphology (88%) was large epithelioid cells with abundant, glassy eosinophilic to vacuolated cytoplasm, prominent nucleoli and well-demarcated cell borders. Multinucleated or binucleated cells, prominent admixed erythrocytic and lymphocytic infiltrates, and intratumoral fat were frequently present. Immunohistochemically, ERG, CD31, and TFE3 were consistently expressed, while expression of CD34 (83%) and cytokeratin AE1/AE3 (20%) was variable. CAMTA1 was negative in all but one case. All cases were confirmed by molecular testing to harbor YAP1-TFE3 gene fusions: majority with YAP1 exon 1 fused to TFE3 exon 4 (88%), or less commonly, TFE3 exon 6 (12%). Most patients (88%) were treated with primary surgical resection. Over a follow-up period of 4-360 months (median 36 months) in 17 cases, 35% of patients remained alive without disease, and 47% survived many years with stable, albeit multifocal and/or metastatic disease. Five-year progression-free survival probability was 88%. We propose categorizing YAP1-TFE3-fused hemangioendothelioma as a distinct disease entity given its unique clinical and histopathologic characteristics in comparison to conventional epithelioid hemangioendothelioma.

Vascular Tumors of Bone: Updates and Diagnostic Pitfall

Vascular tumors of bone can be diagnostically challenging because of their rarity and histologic overlap with diverse mimics. Vascular tumors of bone can be categorized as benign (hemangioma), intermediate-locally aggressive (epithelioid hemangioma), intermediate-rarely metastasizing (pseudomyogenic hemangioendothelioma), and malignant (epithelioid hemangioendothelioma and angiosarcoma). Recurrent genetic alterations have been described, such as FOSB rearrangements in pseudomyogenic hemangioendothelioma and a subset of epithelioid hemangiomas; CAMTA1 or TFE3 rearrangements in epithelioid hemangioendothelioma. This review discusses the clinical, histologic, and molecular features of vascular tumors of bone, along with diagnostic pitfalls and strategies for avoidance.

Loss of expression of YAP1 C-terminus as an ancillary marker for epithelioid hemangioendothelioma variant with YAP1-TFE3 fusion and other YAP1-related vascular neoplasms

Epithelioid hemangioendothelioma (EHE) with YAP1-TFE3 fusion is a recently characterized distinctive variant of EHE that accounts for a small subset (<5%) of cases. It is composed of nests of epithelioid cells with voluminous pale cytoplasm and often shows focally vasoformative architecture. TFE3 immunohistochemistry (IHC) can be used to support the diagnosis; however, studies have questioned its specificity. Yes-associated protein 1 (YAP1), part of the Hippo signaling pathway, is expressed in normal endothelial cells, but becomes disrupted in EHE variant with YAP1-TFE3, such that only a small N-terminal region of YAP1 is expressed in the fusion protein. A recent study also reported YAP1 rearrangements in a subset of retiform and composite hemangioendotheliomas (RHE and CHE). In this study, we evaluated the diagnostic utility of an antibody directed against the C-terminus of YAP1 (YAP1-CT) for EHE with YAP1-TFE3, RHE, and CHE. In total, 78 tumors were included in the study: EHE variant with YAP1-TFE3 (n = 13), conventional (CAMTA1-positive) EHE (n = 20), pseudomyogenic hemangioendothelioma (n = 10), epithelioid hemangioma (n = 19), epithelioid angiosarcoma (n = 10), RHE (n = 4), and CHE (n = 2). IHC was performed using a rabbit monoclonal anti-YAP1 C-terminus antibody. EHE variant showed complete loss of YAP1-CT expression in 10 of 13 (77%) cases. All cases of RHE and CHE, with previously confirmed YAP1 rearrangements, also showed loss of YAP1-CT expression. Loss of YAP1-CT was seen in one conventional EHE (1/20; 5%). All other epithelioid vascular tumors showed retained YAP1-CT expression. Loss of expression of YAP1-CT appears to be associated with good sensitivity and specificity for EHE variant with YAP1-TFE3 fusion and may provide additional support along with TFE3 and CAMTA1 IHC in challenging cases. This marker may also be useful in the diagnosis of RHE and CHE.

Recurrent YAP1-TFE3 Gene Fusions in Clear Cell Stromal Tumor of the Lung

Clear cell (hemangioblastoma-like) stromal tumor of the lung (CCST-L) is a recently described distinctive rare pulmonary neoplasm of unknown histogenesis and molecular pathogenesis. Only 7 cases have been reported in 2 recent studies, although additional cases might have been reported under the heading of extraneural pulmonary hemangioblastoma. We herein describe 4 CCST-L cases, 3 of them harboring a YAP1-TFE3 fusion. The fusion-positive tumors occurred in 3 women, aged 29, 56, and 69 years. All presented with solitary lung nodules measuring 2.3 to 9.5 cm. Histologically, all tumors showed similar features being composed of relatively uniform medium-sized epithelioid to ovoid cells with clear cytoplasm and small round monomorphic nuclei. Scattered larger cells with enlarged hyperchromatic nuclei and marked pleomorphism were noted in 2 cases. The tumors were associated with a hypervascularized stroma with variable but essentially subtle resemblance to capillary hemangioblastoma and perivascular epithelioid cell tumor (PEComa). Immunohistochemistry was negative for all lineage-specific markers. Targeted RNA sequencing showed a YAP1-TFE3 fusion in 3 of 4 cases. All 3 tumors showed homogeneous nuclear TFE3 immunoreactivity. Two patients were disease free at 36 and 12 months. The third patient had biopsy-proven synchronous renal and hepatic metastases, but extended follow-up is not available (recent case). The fourth case lacking the fusion affected a 66-year-old woman and showed subtle histologic differences from the fusion-positive cases, but had comparable TFE3 immunoreactivity. CCST-L represents a distinctive entity unrelated to hemangioblastoma and likely driven by recurrent YAP1-TFE3 fusions in most cases. The relationship of our cases to the recently reported "hemangioblastoma-like" CCST-L remains to be determined. Analysis of larger series is paramount to delineate the morphologic spectrum and biological behavior of this poorly characterized entity.

Primary pleural epithelioid hemangioendothelioma: case report and review of the literature

Epithelioid hemangioendothelioma (EHE) is an extremely rare vascular sarcoma with an unpredictable clinical behavior. Pleural EHEs have been associated with poor response to treatment and reduced survival. To date, no standard treatment for EHE is available. Here we report the case of a 53-year-old man who underwent radical surgery for a symptomatic primary pleural EHE. Clinical presentation was characterized by chronic pain in the left hemithorax with transitory flare, anemia, weight loss and progressive worsening of clinical conditions. After surgery, he resumed active life and normal daily activities and, at 8 months, 18F-FDG PET and computed tomography scan showed no radiological evidence of recurrent disease. Clinical signs of this rare disease, histological features, imaging findings and functional imaging are discussed. We also report a summary of other cases with resected pleural EHE and we briefly review the role of chemotherapeutic, immunomodulatory and antiangiogenic drugs for advanced disease.

Primary Pleural Hemangioendothelioma: A Case Report and Literature Review

Epithelioid hemangioendothelioma (EHE) is a rare tumor of the vascular endothelial cells. It can originate from any tissue; however, it occurs most frequently in the liver and lung. Pleural epithelioid hemangioendothelioma (PEH), EHE developing from pleura, is even more infrequent and less reported in the literature. In the following report, we discuss a 40-year-old man who initially presented with right-sided chest pain. Computed tomography revealed pleural thickening and effusion in his right thoracic cavity. PEH diagnosis was confirmed with immunohistochemistry. In order to provide the readers with an inclusive understanding of the disease, we collected the PEH cases reported in the literature. Despite the scarcity of the reported PEH cases (to our best knowledge), the compiled literature review of the disease enables the readers to grasp a better comprehension of the disease.