WWTR1-CAMTA1 Fusion Research Articles

Clinical efficacy and safety of mTOR inhibitor in patients with advanced unresectable epithelioid hemangioendothelioma (EHE).

e23540 Background: Epithelioidhemangioendothelioma is a rare vascular soft tissue sarcoma, 90% of which contains WWTR1-CAMTA1 fusion gene. Studies have shown that mTOR inhibitors may have a certain effect on EHE patients. Methods: A retrospective analysis of the efficacy and safety of mTOR inhibitor everolimus in the treatment of advanced unresectable epithelioidhemangioendothelioma in our hospital in the past one year. Patients with advanced epithelioidhemangioendothelioma (EHE) confirmed by consultation in the pathological center received this regimen, everolimus 10mg, once a day orally for 28 days, every 4 weeks as a treatment cycle until the disease progressed or showed intolerable toxicity. Results: There were 3 females and 5 males, and their average age was 41.8 years old. All of them were unresectable with liver, lung, and shoulder primary lesions, and lungs, liver, pleura and bone metastasis. Ki67 is from 2% to 10%. 3 patients who received molecular pathological examination were all identified the WWTR1-CAMTA1 fusion gene, and one of them also had EWSR1 chromosome translocation. Previous antineoplastic treatments included gemcitabine, cisplatin, albumin paclitaxel, epirubicin, dacarbazine chemotherapy, anlotinib targeting, and toripalimab immune therapy. 5 patients were treated with first-line drugs, 2 cases with second-line and 1 case with third-line. In terms of overall efficacy, 1 case was not evaluated, 2 cases lost follow-up due to poor tolerance and economic factors, 2 cases were included in the clinical trails after reaching tumor control for 3 months, and the other 3 cases achieved tumor remission with a median PFS of 11.0 months, and the best curative effect was SDa. Severe oral mucositis can greatly affect the medication experience of patients, which can be relieved after symptomatic medication, or when interstitial pneumonia and hemogram decrease significantly, we can consider the oral administration of everolimus 5mg. Conclusions: At present, there is no standard treatment for EHE, we can roughly see the efficacy of mTOR inhibitor everolimus in some EHE patients, mainly disease stability. Emphasis on side effect management, improve tolerance, and systematic treatment of EHE needs to be further explored.

Epitheloid hemangioendothelioma of the urinary bladder: A case report of a rare entity

Epithelioid hemangioendothelioma (EHE) is a rare, often multifocal, intermediate-grade vascular sarcoma arising from the endothelial cells. Their behavior is intermediate between hemangioma and conventional angiosarcoma. Their rarity and unpredictable clinical behavior result in our still limited understanding and treatment options for this variety of tumors. Molecular diagnostic tools like the presence of WWTR1-CAMTA1 fusion have been developed to aid this challenging diagnosis. There is no definitive consensus on the management of patients with this disease and no commonly accepted treatment strategies have been found to be effective, particularly in the metastatic setting. When possible, surgery with clear margins should be considered in case of localized disease. Here, we not only present such a rare case of EHE of the urinary bladder but also provide a comprehensive discussion on the present treatment modalities offered, as found through a thorough search of the published studies. Finally, more studies are required to establish a standard of care for this rare entity.

INTRAOSSEOUS EPITHELIOID HAEMANGIOENDOTHELIOMA OF THE MANDIBLE

Case A fit and well 25-year-old man presented with worsening pain and bony swelling on the lingual aspect of the right premolar region. Radiology showed a multiloculated radiolucent lesion of the anterior mandible with bone expansion and displacement of roots. Initial biopsy revealed fragments of nested epithelioid tumor within the marrow space with extravasated red blood cells and hemosiderin suggestive of vascular origin. Further biopsy showed histologic features of epithelioid haemangioendothelioma (eHAE). Samples were sent to the National Orthopaedic Hospital for molecular testing but this was inconclusive, likely owing to formic acid decalcification. MDT decision for surgical resection was carried out with primary reconstruction. Histology from the resection revealed complete excision of eHAE with focal erosion through the buccal cortex. The patient has recovered well, and to date there is no evidence of recurrence. Discussion eHAE is a very rare vascular tumor of low-grade malignancy, which presents within the lung, liver, or bone including of the head and neck region with 4 cases reported within the mandible. Despite characteristic morphology, diagnosis can be challenging because of small sample size and the rarity of diagnosis. eHAEs are characterized by a WWTR1-CAMTA1 fusion with a minority also showing a YAP1-TFE3 fusion, however decalcification in formic acid can prevent adequate molecular analysis. Conclusions eHAE is a rare tumor with characteristic histologic features and potential for recurrence and metastasis. Molecular testing can assist diagnosis, and development of local tissue pathways for intraosseous tumors that facilitate molecular testing is essential for prompt diagnosis.

1627MO Systemic therapies in advanced epithelioid haemangioendothelioma (EHE): A retrospective international series from the World Sarcoma Network

This observational, retrospective effort across Europe, US and Asia aims to assess the activity of systemic therapies in EHE, a ultra rare sarcoma, marked by WWTR1-CAMTA1 or YAP1-TFE3 fusion, typically metastatic at presentation and with a unpredictable clinical course.

Cytologic features and immunohistochemical findings of epithelioid hemangioendothelioma (EHE) in effusion: A case series.

Epithelioid hemangioendothelioma (EHE) is a rare malignant vascular tumor characterized by WWTR1-CAMTA1, t (1:3) (p36;q25) translocation in 90% of cases. Without prior EHE history, it can mimic other malignant effusions. Recently, CAMTA1 was published as an excellent immunohistochemical surrogate marker for molecular testing for WWTR1-CAMTA1 fusion in surgical specimens. A 6-year retrospective search using our computer system was performed for cases diagnosed as EHE on effusion cytology and surgical specimens. The clinical presentation, cytologic findings and immunohistochemical stain results, including CAMTA1 were reviewed. Four pleural and one peritoneal effusions were identified. The median age was 52 years with a female to male ratio of 3:2. Most patients presented with pulmonary symptoms. The cytologic features were non-specific easily mimicking other malignancies; especially in the absence of known prior malignancy. This was exemplified by one of our cases which was initially misdiagnosed as adenocarcinoma. Intracytoplasmic erythrocytes were present only on the cell blocks but not on cytology. The cytology cell blocks from patients with prior EHE confirmed on surgical biopsies stained positive for vascular markers (CD31, ERG) and CAMTA1. The features of EHE in effusion are non-specific and a diagnostic pitfall in cytology. In the absence of prior EHE diagnosis, inclusion of this entity in the differential diagnoses and application of immunohistochemical stain panels will be prudent in avoiding a misdiagnosis. However, in cases with prior EHE diagnosis, CAMTA1 could serve as diagnostic marker; especially on limited cytology material. Additional studies will be helpful in supporting our results.

Modulation of YAP/ TAZ by statins to improve survival in epithelioid hemangioendothelioma (EHE).

e23527 Background: EHE is a rare soft tissue tumor of endothelial origin. It is distinguished by the pathognomonic WWTR1-CAMTA1 fusion (WWTR1 is the gene symbol for TAZ) seen in 90% of the tumors. YAP1-TFE3 fusion is less common and seen in 10% of the tumors. YAP and TAZ are critical downstream effectors of the Hippo pathway that regulate tumor development, progression, invasion and metastasis by modulating the expression of many Hippo pathway targets. Recent studies have shown that inhibition of HMG-CoA reductase, a key enzyme of the mevalonate pathway, can regulate YAP/ TAZ by preventing their nuclear accumulation and inhibiting their transcriptional activity. This has led to interest in the role of statins, which inhibit HMG-CoA reductase, as a modulator of YAP/ TAZ that could benefit patients with sarcoma, particularly EHE. Methods: A retrospective analysis was performed on patients with a diagnosis of EHE at M D Anderson Cancer Center. Patients were identified using the electronic database system and screened for statin use using EMRs. Demographic and clinical characteristics were tabulated. KM method was used to assess overall survival and log rank test was used to test survival differences between the statin use and non- statin use groups. All statistical analysis was performed using STATA 14. Results: 226 patients with EHE were identified. 27 of them had recorded statin use during the course of their disease. The median OS for the statin use group was not reached and the mean OS was 221 months. The median OS for the non- statin use group was 123.9 months, while the mean OS was 160 months. The difference in OS was not statistically significant between the two groups. The median follow-up time for our cohort was 36.6 months. Conclusions: Our findings indicate a trend towards improved survival for patients with EHE who have received statins over the course of their disease. Our study is limited by a small number of patients who received statins. Prospective studies are required to assess the therapeutic benefit of statins in EHE. [Table: see text]

TFE3 rearranged epithelioid hemangioendothelioma of bone: A clinicopathological, immunohistochemical and molecular study of two cases

Epithelioid hemangioendothelioma (EHE) is a rare malignant angiocentric vascular neoplasm. Around 90% of classic EHE has a t(1;3)(p36;q25) that results in a WWTR1-CAMTA1 fusion gene, a histologically distinctive subset of EHE has been recently shown to have a t(10;14)(p13;q42)that results in a different fusion gene, YAP1-TFE3. Twenty-one cases of TFE3 Rearranged Epithelioid Hemangioendothelioma have been reported in the literature, and only two cases occurred in bone. In the report, we report additional two cases occurred in the femur and skull and review the related literature.

Common Secondary Genomic Variants Associated With Advanced Epithelioid Hemangioendothelioma

Epithelioid hemangioendothelioma (EHE) is a rare, malignant vascular sarcoma characterized in most cases by a WWTR1-CAMTA1 fusion. The clinical course of EHE exhibits a dual nature. The condition is often indolent but can rapidly grow and metastasize unpredictably. No biomarkers to date are available to predict this phenotype. The hypothesis of this study was that better defining the genomic landscape of EHE using next-generation sequencing could offer additional therapies and insight into clinical outcomes. To characterize secondary EHE genomic alterations and their association with clinical outcomes. Multicenter, cross-sectional, retrospective study of next-generation sequencing results collected from participants diagnosed with EHE. Data were abstracted between May 1, 2013, and May 31, 2019. This analysis was conducted from January through June 2019. Summary genomic data were provided by commercial genomic testing companies. Presence or absence of secondary pathogenic genomic variants and their association with disease stage and clinical features. A total of 49 participants with EHE were assessed for the presence or absence of secondary genomic variants. Of these, 32 (65.3%) were female; the mean (SD) age at diagnosis was 49.9 (18.3) years (range, 11-81 years). In all, 46 participants (93.9%) had confirmed WWTR1-CAMTA1 fusion; 26 participants (57.1%) exhibited a pathogenic genomic variant secondary to the WWTR1-CAMTA1 fusion; and 9 participants (18.4%) exhibited potentially targetable genomic variants. Commonly altered genes included CDKN2A/B, RB1, APC, and FANCA. Participants older than 45 years at diagnosis had an increased prevalence of secondary genomic variants that was not statistically significant (65.6% vs 38.5%; difference, 27.1%; 95% CI, -3.5% to 58.0%; P = .16) and were more likely to have a clinically targetable variant (28.1% vs 0%; difference, 28.1%; 95% CI, 11.2%-40.2%; P = .03). In 14 participants with clinical data available, those with stage III/IV EHE were more likely to exhibit a secondary pathogenic genomic variant (80% vs 0%; difference, 80%; 95% CI, 55.2%-100%; P = .006). Participants with stage III/IV EHE were diagnosed at an older age (mean [SD] age, 54.6 [14.1] years vs 31.7 [16.0] years; P = .05) and had elevated WWTR1-CAMTA1 fusion expression that was not statistically significant (mean [SD] expression, 677 [706] copies vs 231 [213] copies; P = .20). Although EHE exhibits few secondary genomic variants, presence of key secondary variants may be prognostic for aggressive EHE. Further research is needed to confirm this finding and determine whether more intensive upfront treatment is necessary for these patients.

Atypical epithelioid hemangioendothelioma: a clinicopathological analysis of eight cases

Objective: To study the clinicopathological features, diagnosis, and differential diagnosis of atypical epithelioid hemangioendothelioma (EHE). Methods: Eight cases of atypical EHEs were collected from Jiangsu Province Hospital (the First Affiliated Hospital of Nanjing Medical University) between 2010 and 2018. EnVision method and fluorescence in situ hybridization (FISH) were used to detect immunophenotype, WWTR1-CAMTA1 and TFE3 gene rearrangement, respectively. Results: There were 4 males and 4 females, ranging from 42 to 59 years (median 47.5 years). The tumors located in soft tissue (3 cases), lung (3 cases), liver (1 case) and chest wall (1 case). One soft tissue EHE involved also adjacent fibula and pleural involvement was present in all three lung cases at the diagnosis. Regional lymph node metastases were present in two cases (one involving soft tissue tumor and one involving liver). Morphologically, the tumor cells were epithelioid with abundant eosinophilic cytoplasm, moderate to marked nuclear pleomorphism, irregular nuclear membrane, unevenly chromatin, and prominent nucleoli. The cells arranged in cords, small nests or solid pattern. The mitotic rate was 4.3 mitoses/2 mm(2) on average (ranging 2 to 9). Tumor necrosis was seen in every case. Among all 8 cases, blister cells were found upon careful observation. Myxohyaline stroma was present in 6 cases. Immunohistochemically, tumor cells expressed CD31 (8/8), CD34 (7/8), ERG (8/8), CKpan (2/7), and CAMTA1 (4/6). None of the tested cases stained for TFE3 (0/6). WWTR1-CAMTA1 fusion gene by FISH was found in all tested 6 cases and TFE3 gene rearrangement was not detected in any. Available clinical follow-up was obtained in 7 cases and the intervals range from 6 to 55 months (average 19.6 months). Six patients had metastasis and 3 patients died of disease. One patient was alive with no evidence of disease. Conclusions: Atypical EHE is a more aggressive tumor than classic EHE, with histological features including high nuclear grade, increased mitotic activity, the presence of solid growth pattern and tumor necrosis. The differential diagnoses include epithelioid angiosarcoma, carcinoma and epithelioid sarcoma.

Determinants of secondary alterations in WWTR1-CAMTA1 fusion epithelioid hemangioendothelioma.

11045 Background: Epithelioid hemangioendothelioma (EHE) is a rare vascular sarcoma characterized by the WWTR1- CAMTA1 fusion ( WC-F) in a majority of cases. EHE demonstrates a biphasic clinical course; remaining indolent for many years before suddenly demonstrating aggressive progression. Cell cycle mutations have been previously noted to account for some secondary alterations; however, little is known regarding the chronicity of these secondary alterations or their clinical implications. Here we present the largest assessment of secondary genomic variants and their clinical import. Methods: Comprehensive genomic profiling from 45 WC-F positive EHE patients (pts) were provided by Foundation Medicine (FMI). 8 of these 45 pts were treated at The Ohio State University (OSU) and were evaluated retrospectively through chart review. Known deleterious alterations, variants of unknown significance (VUS), and genomic copy quantification for the WC-F was included in our analysis. Targetable gene variants were defined by OncoKB. Chi-square and student’s t-tests were used as appropriate. Results: Genomic copy number of the WC-F best fit a log-normal distribution (range: 13-2,131 copies). 20 pts (44%) did not exhibit any secondary genomic variants. The most commonly altered genes included: CDKN2A/B (7 variants), RB1 (3 variants), and ATRX (3 variants). Commonly identified pathways included: cell cycle (9 pts, 20.0%), epigenetic modulators (7 pts, 15.6%), and DNA damage repair (7 pts, 15.6%). Eight pts exhibited targetable gene variants (18%) as defined by OncoKB. Subjects ≥50 years of age exhibited a greater proportion of clinically targetable variants (27.6% vs 0%; p = 0.02). Pts with a secondary genomic variant exhibited elevated WC-F copy numbers (p < 0.001). OSU pts with aggressive EHE were more likely to have a second genomic variant (80% vs 0%; p = 0.03) when compared to indolent EHE, with trends toward higher WC-F copy numbers (809±315 vs 207±147; p = 0.2) and older age at diagnosis (59.5±5.5 vs 36.7±8.8; p = 0.1). Conclusions: In this study, secondary genomic variants in WC-F driven EHE are more common in older patients ( > 50 yo). Further, the presence of secondary genomic variants is associated with an aggressive phenotype and may drive poor prognosis. Prospective research is needed to confirm these findings.

CAMTA-1 Expression in 24 Cases of Hepatic Epithelioid Hemangioendothelioma in a Single Institute: Diagnostic Utility for Differential Diagnosis from Hepatic Angiosarcoma

Epithelioid hemangio-endothelioma (EHE) of the liver is an uncommon vascular tumor with variable clinical courses ranging from stable disease to fatal outcome. EHE can mimic epithelioid angiosarcoma, which has a more aggressive behavior, especially in a small biopsy sample. EHEs are known to have the WWTR1-CAMTA1 fusion gene, and nuclear expression of CAMTA1 by immunohistochemistry (IHC) has been reported in about 90% of EHEs in multiple organs. Our study aimed to validate the diagnostic utility of CAMTA1 expression in EHEs, especially in the liver. IHC was performed using anti-CAMTA1 antibody in 34 tumors (24 hepatic EHEs and 10 angiosarcomas). In CAMTA1-negative EHEs, TFE3 IHC was performed. Of the 24 hepatic EHEs, 22 (91.6%) showed nuclear staining for CAMTA1. One of two CAMTA1-negative cases showed TFE3 positivity. The other case was negative for TFE3. Meanwhile, all 10 angiosarcoma cases had no CAMTA1 expression. CAMTA1 is a highly sensitive and specific marker for diagnosis of hepatic EHE. It is helpful for differentiation of hepatic EHE and angiosarcoma, especially in small biopsy samples.

Two cases of WWTR1-CAMTA-1 fusion-positive epithelioid hemangioendotheliomas with extremely different outcomes

We report two cases of WWTR1-CAMTA1 fusion-positive epithelioid hemangioendotheliomas (EHEs) with extremely different clinical behaviors. The first case was a 52-year-old Japanese woman with a complaint of an enlarging right axillary mass. Surgical specimen showed that the epithelioid tumors within the vein had the pathological feature of a cord-like pattern with myxoid or hyaline matrix and the intracytoplasmic lumen with erythrocytes and the immunophenotype of endothelial cells. The final pathological diagnosis was classic EHE. An RT-PCR analysis showed positivity of WWTR1-CAMTA1 fusion. The patient has now been free of disease for 7 years after surgery. The second case was a 70-year-old Japanese male with a complaint of severe pain of his left thigh. The radiographic findings showed ectopic calcification near the left femur. Surgical specimen showed clusters of malignant epithelioid cells with necrosis and obvious mitoses in soft tissue. They were also shown to be of endothelial origin by immunohistochemistry (IHC). The pathological diagnosis was malignant EHE or epithelioid angiosarcoma with ectopic ossification. An RT-PCR analysis showed the tumor had WWTR1-CAMTA1 fusion. Thus, the final pathological diagnosis was malignant EHE. Unfortunately, he died 7 months after surgery due to pleural dissemination. Although fusion gene is thought to define one spectrum of specific tumors, our two cases of EHEs with WWTR1-CAMTA1 fusion showed extremely different outcomes, one is rather benign and the other fatal. Retrospective study showed that both tumors were positive for nuclear CAMTA1 by IHC. Fusion-genes define a unique spectrum of tumors, but even in the tumors within the same spectrum defined by a specific fusion-gene, there are heterogeneities of malignant potentials. Therefore, factors other than fusion-genes may contribute to prognoses.

Advances in the clinicopathological and molecular classification of cutaneous mesenchymal neoplasms.

In recent years, there have been several important refinements in the classification of cutaneous mesenchymal neoplasms, including the description of new tumour types, along with the identification of novel and recurrent molecular genetic findings. In addition to providing new insights into tumour biology, many of these advances have had significant clinical consequences with regard to diagnostics, management, and prognostication. Newly described entities include pseudomyogenic haemangioendothelioma, haemosiderotic fibrolipomatous tumour, and fibroblastic connective tissue naevus, which are reviewed in the context of the principal differential diagnoses and significant clinical implications. Genetic characterization of several soft tissue tumour types that occur in the skin has resulted in the identification of diagnostically useful markers: ALK gene rearrangement with corresponding ALK protein expression by immunohistochemistry in epithelioid fibrous histiocytoma; the WWTR1-CAMTA1 fusion gene with CAMTA1 protein expression in epithelioid haemangioendothelioma; MYC amplification and overexpression in radiation-associated angiosarcoma; and EWSR1 gene rearrangement in cutaneous myoepithelial tumours. Finally, the classification of intradermal smooth muscle tumours and unclassified/pleomorphic dermal sarcoma has been refined, resulting in both improved classification and improved prognostication. Many of the tumour types listed above are encountered not only by specialist dermatopathologists, but also by practising general surgical pathologists, and this review should therefore provide a widely applicable update on the histological and molecular classification of cutaneous mesenchymal neoplasms, along with the appropriate use of ancillary diagnostic tests, in particular immunohistochemistry, in the evaluation of such lesions and their histological mimics.

Hepatic Epithelioid Hemangioendothelioma with Cecal Metastasis in a Natural Course: A Case Report

Epithelioid hemangioendothelioma (EHE) is a rare vascular tumor of low malignant potential that occurs mostly in soft tissue. So far, only two cases of EHE involving the intestine have been recorded. Here, we describe a rare case of cecal EHE due to a subsequent metastasis from the primary liver tumor three years after initial diagnosis. A 74- year-old man had sudden onset of epigastralgia for 24 hours. The abdominal CT revealed an ileocecal mass with a small bowel obstruction, and extensive tumor involvement in the liver was noted. He received an emergent right hemicolectomy for relief of the ileus. Unfortunately, he expired four days later due to septic shock. The pathologic diagnosis of EHE prompted a molecular study for a WWTR1-CAMTA1 fusion. The Sanger sequencing results showed the fusion involved exon 4 of WWTR1 with exon 8 of CAMTA1. There is no standard treatment for hepatic EHE because of its rarity and variable clinical outcome. The decision on a treatment strategy should be individualized for each patient. Since the patient received supportive care only for the liver tumor, this case demonstrated a natural course of hepatic EHE with a survival of more than 3.3 years.

Molecular characterization of epithelioid haemangioendotheliomas identifies novel WWTR1-CAMTA1 fusion variants.

Epithelioid haemangioendothelioma (EHE) is a malignant vascular neoplasm. Subsets have been characterized previously by translocations resulting in either WWTR1-CAMTA1 or YAP1-TFE3 fusion. We sought to develop molecular and immunohistochemical (IHC) assays to aid in the diagnosis and characterization of EHE. Fifty-two formalin-fixed, paraffin-embedded (FFPE) cases diagnosed between 2002 and 2014 were retrieved from the pathology files of our institutions. Reverse transcription-polymerase chain reaction (RT-PCR) assays were optimized to detect WWTR1-CAMTA1 and YAP1-TFE3 fusion transcripts in FFPE tissue and transcription factor E3 (TFE3) protein accumulation was examined by immunohistochemistry (IHC). RNA was extracted from 33 adequate samples, with more recent cases providing a greater yield of high quality RNA. Fourteen of 18 informative cases were positive for WWTR1-CAMTA1 fusion transcripts, four of which showed higher-grade cytological features termed by some as 'malignant EHE'. Novel in-frame fusion transcripts were identified in four cases by direct sequencing. IHC revealed variable nuclear TFE3 staining in six of 17 cases; three with patchy staining showed WWTR1-CAMTA1 fusion. One of 18 informative cases was positive for YAP1-TFE3 fusion and showed strong nuclear TFE3 staining by IHC. This study confirms the high incidence of WWTR1-CAMTA1 and YAP1-TFE3 rearrangements in EHE and indicates that the staining pattern for TFE3 IHC is critical for specificity.

Epithelioid Hemangioendothelioma: clinicopathologic, immunhistochemical, and molecular genetic analysis of 39 cases.

BackgroundEpithelioid hemangioendothelioma is a malignant, often indolent vascular tumor which occurs at various anatomic sites. Based on a reciprocal translocation t (1;3)(p36;q25), a consistent WWTR1-CAMTA1 fusion gene has been found. An alternate YAP1-TFE3 fusion has been detected in a small and distinct subset of cases.MethodsThirty-nine tumors, from 24 females and 15 males with an age range 9–85 years, were located in soft tissue (head and neck [8], trunk [5], upper extremities [3], lower extremities [2], mediastinal [1], and paratesticular [1]), lymph node (1), breast (1), skin (2), bone (6), lung (7), and liver (2). The cases were investigated using a panel of immunohistochemical markers. The aforementioned fusion-genes were examined using RT-PCR and/or FISH in order to validate their diagnostic value.ResultsFollow-up available for 17 patients ranged from 3 months to 7 years (median interval 1.5 years). Eleven patients were alive without disease, 2 patients were alive with disease after 1.5 and 2 years, respectively. Four patients died of disease after 4 months (n = 1), 5 months (n = 2), and 1.5 years (n = 1).The size, known for 30 lesions, was >3 cm in 9 of them. Histologically, all lesions had classical features, at least focally. Four tumors counted >3 mitoses/50 HPF.Immunohistochemically, all cases tested stained positive for ERG (21), FLI1 (5) and CD31 (39). CD34 and D2-40 positivity was seen in 81% and 71% of the examined cases, respectively. 11/35 cases expressed pan-keratin and 6/20 cases CK8.18. TFE3 showed a nuclear reaction in 21/24 cases, irrespective of TFE3 rearrangement.Molecular genetically, 35/35 cases revealed one of the fusion genes by FISH and/or RT-PCR with WWTR1-CAMTA1 in 33 cases and YAP1-TFE3 in 2 cases.ConclusionsThese results demonstrate the high diagnostic value of FISH and RT-PCR in detecting the fusion genes of EHE. The immunohistochemical utility of TFE3 appears questionable in this study.Virtual SlidesThe virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/4010279141259481

Malignant vascular tumors—an update

Although benign hemangiomas are among the most common diagnoses amid connective tissue tumors, sarcomas showing endothelial differentiation (ie, angiosarcoma and epithelioid hemangioendothelioma) represent under 1% of all sarcoma diagnoses, and thus it is likely that fewer than 500 people in the United States are affected each year. Differential diagnosis of malignant vascular tumors can be often quite challenging, either at the low end of the spectrum, distinguishing an epithelioid hemangioendothelioma from an epithelioid hemangioma, or at the high-grade end of the spectrum, between an angiosarcoma and a malignant epithelioid hemangioendothelioma. Within this differential diagnosis both clinico-radiological features (ie, size and multifocality) and immunohistochemical markers (ie, expression of endothelial markers) are often similar and cannot distinguish between benign and malignant vascular lesions. Molecular ancillary tests have long been needed for a more objective diagnosis and classification of malignant vascular tumors, particularly within the epithelioid phenotype. As significant advances have been recently made in understanding the genetic signatures of vascular tumors, this review will take the opportunity to provide a detailed update on these findings. Specifically, this article will focus on the following aspects: (1) pathological and molecular features of epithelioid hemangioendothelioma, including the more common WWTR1–CAMTA1 fusion, as well as the recently described YAP1–TFE3 fusion, identified in a morphological variant of epithelioid hemangioendothelioma; (2) discuss the heterogeneity of angiosarcoma clinical, morphological and genetic spectrum, with particular emphasis of MYC and FLT4 gene amplification in radiation-induced angiosarcoma; and (3) provide a practical guide in the differential diagnosis of epithelioid vascular tumors using molecular testing.

Novel YAP1‐TFE3 fusion defines a distinct subset of epithelioid hemangioendothelioma

Conventional epithelioid hemangioendotheliomas (EHE) have a distinctive morphologic appearance and are characterized by a recurrent t(1;3) translocation, resulting in a WWTR1-CAMTA1 fusion gene. We have recently encountered a fusion-negative subset characterized by a somewhat different morphology, including focally well-formed vasoformative features, which was further investigated for recurrent genetic abnormalities. Based on a case showing strong transcription factor E3 (TFE3) immunoreactivity, fluorescence in situ hybridization (FISH) analysis for TFE3 gene rearrangement was applied to the index case as well as to nine additional cases, selected through negative WWTR1-CAMTA1 screening. A control group, including 18 epithelioid hemangiomas, nine pseudomyogenic HE, and three epithelioid angiosarcomas, was also tested. TFE3 gene rearrangement was identified in 10 patients, with equal gender distribution and a mean age of 30 years old. The lesions were located in somatic soft tissue in six cases, lung in three and one in bone. One case with available frozen tissue was tested by RNA sequencing and FusionSeq data analysis to detect novel fusions. A YAP1-TFE3 fusion was thus detected, which was further validated by FISH and reverse transcription polymerase chain reaction (RT-PCR). YAP1 gene rearrangements were then confirmed in seven of the remaining nine TFE3-rearranged EHEs by FISH. No TFE3 structural abnormalities were detected in any of the controls. The TFE3-rearranged EHEs showed similar morphologic features with at least focally, well-formed vascular channels, in addition to a variably solid architecture. All tumors expressed endothelial markers, as well as strong nuclear TFE3. In summary, we are reporting a novel subset of EHE occurring in young adults, showing a distinct phenotype and YAP1-TFE3 fusions.

Sirolimus in advanced hemangioendothelioma.

10565 Background: Haemangioendothelioma (HE) is a very rare vascular tumor. The epithelioid variant is characterized by a specific t(1;3)(p36.3;q25) translocation, resulting in the WWTR1-CAMTA1 fusion product. We retrospectively reviewed patients with HE treated with sirolimus, an mTOR inhibitor, at our institution. Methods: We identified 12 patients (M/F: 4/8 – mean age: 46 years – epithelioid HE/ retiform HE: 10/2 – locally advanced/multifocal: 1/11 – pretreated: 6) with advanced HE who were treated with sirolimus, as a single agent, 5 mg/day, from 2005 on. They had evidence of progression in the 3 months before starting treatment. The daily dose of sirolimus was adjusted according to drug blood levels (range 10-20 ng/dl). Response was evaluated with CT/MRI/PET scans after 4-6 weeks of treatment, then every 3 months, by RECIST and Choi criteria. WWTR1 gene rearrangement was evaluated by FISH, and the histochemical expression of mTOR effectors, S6 and 4BP1, is ongoing. Results: 10 patients are evaluable for response (2 pts are too early). Sirolimus daily dose ranged from 3 to 6 mg/day. Best response by RECIST was PR = 1, SD = 6 (all >6 months, range 6-48+), PD = 3 cases. In 3 cases, a Choi response could be detected. PET response was observed in 6/6 evaluated case. Median PFS (range) was 24 (3-48) months. Two patients with evidence of tumor stabilization while under sirolimus stopped their treatment after 12 and 24 months of therapy, respectively, with evidence of interval progression in both. A new disease stabilization was obtained after restoring sirolimus. Conclusions: HE is known for its potentially long-lasting course, even in typical cases with multicentric/multifocal disease. Progressive HE may require a medical therapy, but is insensitive to cytotoxic chemotherapy, while mainly andecdotal responses were reported to interferon, bevacizumab and thalidomide. In this retrospective series, sirolimus resulted in a high proportion of mainly non-dimensional, possibly long-lasting, tumor responses.

Monoclonality of multifocal epithelioid hemangioendothelioma of the liver by analysis of WWTR1-CAMTA1 breakpoints

Similar to other vascular tumors, epithelioid hemangioendothelioma (EHE) can have multifocal presentation in up to 50% of cases. However, whether multifocal EHE represents an unusual pattern of metastasis or multiple separate primary tumors remains to be elucidated. Our recent identification of a WWTR1-CAMTA1 fusion as the genetic hallmark of EHE irrespective of anatomic location was used to clarify this question by comparing the similarity of translocation breakpoints. In our previous study, we found variability of the fusion transcripts of the t(1;3)(p36;q25) translocation among different patients with EHE. Thus, we undertook a molecular analysis of six samples from two patients with multicentric hepatic EHE to test our hypothesis that the presence of identical breakpoints in WWTR1 and CAMTA1 support the monoclonal nature of multifocal EHE. Using reverse transcription-polymerase chain reaction (RT-PCR) and subsequent sequencing, we confirmed an identical WWTR1-CAMTA1 fusion transcript product from different nodules in each patient. Our results confirm that multifocal EHE are monoclonal and thus represent metastatic implants of the same neoplastic clone rather than a "field-effect" or synchronous occurrence of multiple neoplastic clones.