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.

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.

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.

Gene fusions in vascular tumors and their underlying molecular mechanisms.

INTRODUCTION: The group of vascular tumors contains many different entities, and is considered difficult by pathologists, as they often have overlapping histological characteristics. Chromosomal translocations have been identified in ~20% of mesenchymal tumors and are considered the drivers of tumor formation. Many translocations have been discovered over the past decade through next-generation sequencing. This technological advancement has also revealed several recurrent gene fusions in vascular tumors. AREAS COVERED: This review will discuss the various vascular tumors for which recurrent gene fusions have been identified. The gene fusions and the presumed molecular mechanisms underlying tumorigenesis are shown, and potential implications for targeted therapies discussed. The identification of these gene fusions in vascular tumors has improved diagnostic accuracy, especially since several of these fusions can be easily detected using surrogate immunohistochemical markers. EXPERT OPINION: The identification of gene fusions in a subset of vascular tumors over the past decade has improved diagnostic accuracy, and has provided the pathologists with novel diagnostic tools to accurately diagnose these often difficult tumors. Moreover, the increased understanding of the underlying molecular mechanisms can guide the development of targeted therapeutic strategies.

Current progress and future perspectives of research on intravascular large B-cell lymphoma.

Intravascular large B-cell lymphoma is a rare disease of the large B cells characterized by selective growth in the lumina of small vessels in systemic organs. Since first reported in 1959, the difficulty of obtaining sufficient tumor cells from biopsy specimens has hampered the elucidation of its underlying biology. Recent progress using xenograft models and plasma cell-free DNA has uncovered genetic features that are similar to those of activated B-cell type diffuse large B-cell lymphoma, including MYD88 and CD79B mutations and frequent alterations in immune check point-related genes such as PD-L1 and PD-L2. Given the improvement in clinical outcomes and a higher risk of secondary central nervous system (CNS) involvement in the rituximab era, a phase 2 trial of R-CHOP combined with high-dose methotrexate and intrathecal chemotherapy as a CNS-oriented therapy has been conducted. This trial, the PRIMEUR-IVL study, has displayed good progression-free survival and a low cumulative incidence of secondary CNS involvement. Long-term follow-up within this trial is still ongoing. Further understanding of the pathophysiology of the disease and improvements in clinical outcomes are still needed.

Modern multimodality management of patients with caval leiomyosarcoma: New treatment paradigms and potential molecular insights.

BACKGROUND AND OBJECTIVES: Caval leiomyosarcomas (cLMS) are rare soft tissue sarcomas historically associated with high recurrence rates and poor prognosis. While radical resection remains the mainstay of therapy for cLMS, new systemic therapies have presented opportunities for multimodality treatment. We examined the clinical outcomes of patients with cLMS treated with modern, multimodality approaches, and compared their outcomes to those of patients with noncaval retroperitoneal LMS (ncLMS). METHODS: A retrospective, single-institution review identified all patients diagnosed with primary retroperitoneal LMS from 2012 to 2018. Radiographic and pathologic review distinguished patients with cLMS and ncLMS. Standard clinicopathologic variables and response to chemotherapy (when applicable) were analyzed. Primary endpoints were overall (OS) and progression-free survival (PFS). RESULTS: Eleven patients with cLMS were identified. Median tumor size was 7.5 cm (IQR, 5.0-14.3 cm); all patients had Stage II/III disease. Seven patients received neoadjuvant chemotherapy. Nine cLMS patients underwent R0/R1 resection; two did not complete resection. Six patients received adjuvant systemic therapy. Twenty patients with ncLMS were treated during the same period. No statistical intergroup differences were noted in tumor size, pathologic grade, stage, or resection margin status. Patients with ncLMS were less likely to receive neoadjuvant (10% vs. 64%) and adjuvant chemotherapy (30% vs. 55%). Two-year OS (81% vs. 78%; p = NS) and PFS (55% vs. 46%; p = NS) were comparable between cLMS and ncLMS patients. CONCLUSIONS: Multimodality treatment with systemic therapy and aggressive surgical resection may achieve equivalent survival outcomes for patients with cLMS versus similar ncLMS. We recommend that all patients with cLMS be evaluated for multidisciplinary treatment. Genomic and proteomic expression profiling may identify novel or targetable mutations.

Genomically Complex Human Angiosarcoma and Canine Hemangiosarcoma Establish Convergent Angiogenic Transcriptional Programs Driven by Novel Gene Fusions.

Sporadic angiosarcomas are aggressive vascular sarcomas whose rarity and genomic complexity present significant obstacles in deciphering the pathogenic significance of individual genetic alterations. Numerous fusion genes have been identified across multiple types of cancers, but their existence and significance remain unclear in sporadic angiosarcomas. In this study, we leveraged RNA-sequencing data from 13 human angiosarcomas and 76 spontaneous canine hemangiosarcomas to identify fusion genes associated with spontaneous vascular malignancies. Ten novel protein-coding fusion genes, including TEX2-PECAM1 and ATP8A2-FLT1, were identified in seven of the 13 human tumors, with two tumors showing mutations of TP53. HRAS and NRAS mutations were found in angiosarcomas without fusions or TP53 mutations. We found 15 novel protein-coding fusion genes including MYO16-PTK2, GABRA3-FLT1, and AKT3-XPNPEP1 in 11 of the 76 canine hemangiosarcomas; these fusion genes were seen exclusively in tumors of the angiogenic molecular subtype that contained recurrent mutations in TP53, PIK3CA, PIK3R1, and NRAS. In particular, fusion genes and mutations of TP53 cooccurred in tumors with higher frequency than expected by random chance, and they enriched gene signatures predicting activation of angiogenic pathways. Comparative transcriptomic analysis of human angiosarcomas and canine hemangiosarcomas identified shared molecular signatures associated with activation of PI3K/AKT/mTOR pathways. Our data suggest that genome instability induced by TP53 mutations might create a predisposition for fusion events that may contribute to tumor progression by promoting selection and/or enhancing fitness through activation of convergent angiogenic pathways in this vascular malignancy. IMPLICATIONS: This study shows that, while drive events of malignant vasoformative tumors of humans and dogs include diverse mutations and stochastic rearrangements that create novel fusion genes, convergent transcriptional programs govern the highly conserved morphologic organization and biological behavior of these tumors in both species.

[Clinicopathological characteristics of pulmonary artery intimal sarcoma].

Objective: To describe the clinicopathological features of pulmonary artery intimal sarcoma (PAIS), and to understand its molecular alterations. Methods: Sixty cases of pulmonary artery endarterectomy performed at the China-Japan Friendship Hospital, Beijing, China from January 2017 to January 2020 were reviewed. Clinical data of 5 patients with pulmonary artery intimal sarcoma were collected. Hematoxylin-eosin staining, immunohistochemistry staining and fluorescence in situ hybridization (FISH) were performed to evaluate the pathological features. RNA sequencing was conducted to assess the fusion gene changes in PAIS. Results: The detection rate of PAIS was 8.3% (5/60), with the median age of 49 years and a female predominance. Their clinical manifestations were non-specific. Histopathological examination showed that the tumors were composed of malignant spindle or epithelioid cells, with various degrees of atypia. Focal heterologous osteosarcomatous or leiomyosarcomatous differentiation was noted. The tumor cells could express PDGFRA, CDK4 and MDM2 with co-amplification of MDM2, CDK4 and EGFR genes. RNA sequencing detected multiple in-frame fusions in the tumors. Conclusions: PAIS is a rare, highly heterogeneous, and poorly-or un-differentiated sarcoma accompanied by complex changes of multiple genes.It has no known effective treatments, and thus has a poor prognosis.

Frequent genetic alterations in immune checkpoint-related genes in intravascular large B-cell lymphoma.

Intravascular large B-cell lymphoma (IVLBCL) is a unique type of extranodal lymphoma characterized by selective growth of tumor cells in small vessels without lymphadenopathy. Greater understanding of the molecular pathogenesis of IVLBCL is hampered by the paucity of lymphoma cells in biopsy specimens, creating a limitation in obtaining sufficient tumor materials. To uncover the genetic landscape of IVLBCL, we performed whole-exome sequencing (WES) of 21 patients with IVLBCL using plasma-derived cell-free DNA (cfDNA) (n = 18), patient-derived xenograft tumors (n = 4), and tumor DNA from bone marrow (BM) mononuclear cells (n = 2). The concentration of cfDNA in IVLBCL was significantly higher than that in diffuse large B-cell lymphoma (DLBCL) (P < .0001) and healthy donors (P = .0053), allowing us to perform WES; most mutations detected in BM tumor DNA were successfully captured in cfDNA and xenograft. IVLBCL showed a high frequency of genetic lesions characteristic of activated B-cell-type DLBCL, with the former showing conspicuously higher frequencies (compared with nodal DLBCL) of mutations in MYD88 (57%), CD79B (67%), SETD1B (57%), and HLA-B (57%). We also found that 8 IVLBCL (38%) harbored rearrangements of programmed cell death 1 ligand 1 and 2 (PD-L1/PD-L2) involving the 3' untranslated region; such rearrangements are implicated in immune evasion via PD-L1/PD-L2 overexpression. Our data demonstrate the utility of cfDNA and imply important roles for immune evasion in IVLBCL pathogenesis and PD-1/PD-L1/PD-L2 blockade in therapeutics for IVLBCL.

Cytogenetic complexity and heterogeneity in intravascular lymphoma.

AIMS: To characterise the karyotypic abnormalities and heterogeneities in intravascular lymphoma (IVL). METHODS: G-banded karyotyping was performed on biopsy specimens from a single-centre IVL cohort comprising intravascular large B-cell lymphoma (IVLBCL, n=12) and NK/T-cell lymphoma (IVNKTCL, n=1). RESULTS: Five IVLBCL cases and one IVNKTCL case (total 46%) were found to have normal karyotypes, and the cytogenetic abnormalities observed in the other seven IVLBCL cases (54%) were investigated further. These seven karyotypes were uniformly complex with an average of 13 aberrations. The seven cases all had abnormalities involving chromosome 6, with 57% involving structural abnormalities at 6q13, and chromosome 8, with 43% involving abnormalities at 8p11.2. In addition, 71% had aberrations at 19q13. On average, 4.4 chromosomal gains and losses were detected per case. Cytogenetic heterogeneities were observed in six cases (86%) and tetraploidy in three cases (43%). There was no significant difference in progression-free survival (p=0.92) and overall survival (p=0.61) between the IVLBCL cases with complex and normal karyotypes. CONCLUSION: Approximately half of IVLBCL cases had a highly heterogeneous pattern of karyotypes with different clonal numerical and structural chromosome aberrations.

Multiple paragangliomas: a case report.

BACKGROUND: Carotid and vagal paragangliomas (CPGLs and VPGLs) are rare neoplasms that arise from the paraganglia located at the bifurcation of carotid arteries and vagal trunk, respectively. Both tumors can occur jointly as multiple paragangliomas accounting for approximately 10 to 20% of all head and neck paragangliomas. However, molecular and genetic mechanisms underlying the pathogenesis of multiple paragangliomas remain elusive. CASE PRESENTATION: We report a case of multiple paragangliomas in a patient, manifesting as bilateral CPGL and unilateral VPGL. Tumors were revealed via computed tomography and ultrasound study and were resected in two subsequent surgeries. Both CPGLs and VPGL were subjected to immunostaining for succinate dehydrogenase (SDH) subunits and exome analysis. A likely pathogenic germline variant in the SDHD gene was indicated, while likely pathogenic somatic variants differed among the tumors. CONCLUSIONS: The identified germline variant in the SDHD gene seems to be a driver in the development of multiple paragangliomas. However, different spectra of somatic variants identified in each tumor indicate individual molecular mechanisms underlying their pathogenesis.

Intravenous leiomyomatosis is inclined to a solid entity different from uterine leiomyoma based on RNA-seq analysis with RT-qPCR validation.

INTRODUCTION: Intravenous leiomyomatosis (IVL) is currently regarded as a special variant of the common uterine leiomyoma (LM). Though IVL shows a similar histological morphology to LM, IVL is characterized by unique intravenous growth patterns and low-grade malignant potential, which are quite different from LM. There are currently few studies underlying the molecular alterations of IVL, though this information is important for understanding the pathogenesis of the disease, and for identifying potential biomarkers. METHOD: We carried out a high-throughput whole transcriptome sequencing of tumor and normal tissue samples from five IVL patients and five LM patients and compared the differentially expressed genes (DEGs) between IVL and leiomyoma. We performed multiple different enrichment and target analyses, and the expression of selected DEGs was validated using RT-qPCR in formalin-fixed samples. RESULTS: Our study identified substantial different genes and pathways between IVL and LM, and functional enrichment analyses found several important pathways, such as angiogenesis and antiapoptosis pathways, as well as important related genes, including SH2D2A, VASH2, ADAM8, GATA2, TNF, and the lncRNA GATA6-AS1, as being significantly different between IVL and LM (P = .0024, P = .0195, P = .0212, P = .0435, P = .0401, and P = .0246, respectively). CXCL8, LIF, CDKN2A, BCL2A1, COL2A1, IGF1, and HMGA2 were also differently expressed between IVL and LM groups, but showed no statistical difference (P = .2409, P = .1773, P = .0596, P = .2737, P = .1553, P = .1045, and P = .1847, respectively) due to the large differences among individuals. Furthermore, RT-qPCR results for five selected DEGs in IVL tissues and adjacent nontumor tissues were mainly consistent with our sequencing results. CONCLUSION: Our results indicated that IVL may be a solid entity that is unique and different from LM, proving consistent with previous studies. Furthermore, we identified DEGs, particularly within angiogenesis and antiapoptosis pathway-related genes that may play crucial roles in the development and pathogenesis of IVL and may be potential specific biomarkers.

MED12 exon 2 mutation is uncommon in intravenous leiomyomatosis: clinicopathologic features and molecular study.

Intravenous leiomyomatosis (IVL) is a rare neoplasm that is characterized by smooth muscle cell proliferation within venous vessels. The aim of this study is to investigate the clinicopathological features, immunophenotypes, and MED12 gene mutations in IVL. Nine cases of IVL from the Affiliated Hospital of Qingdao University were collected, and the clinicopathological features were reviewed. The immunohistochemical expressions of p16, phosphatase and tensin homolog deleted on chromosome 10 (PTEN), alpha thalassemia/mental retardation syndrome X-linked (ATRX), retinoblastoma 1 (RB1), fumarate hydratase (FH), and p53, were evaluated. The mutation status of MED12 gene exon 2 was detected by Sanger sequencing. All the 9 patients were women ranging from 32 to 58 years, and uterine leiomyomas were identified in 5 patients. Immunohistochemical staining showed that all IVL and leiomyoma samples were positive for estrogen receptor and progesterone receptor, but negative for CD34. IVL displayed similar immunostaining patterns with their uterine counterparts with focal p16 immunostaining. FH, PTEN, ATRX, and RB1 were variably positive, and p53 and Ki-67 positive rates were less than 5% in all cases. Two novel genetic variations at MED12 exon 2, a synonymous mutation c.141C>T (p.Asn47=), and an in-frame deletion mutation c.133_147del15 (p.Phe45_Pro49del) were identified in two IVL cases. One missense mutation c.131G>A (p.Gly44Asp) was identified in one uterine leiomyoma. The remaining 11 tumor samples (7 IVL cases and 4 uterine leiomyomas) showed no mutations at MED12 exon 2. Our results showed two novel MED12 mutations in IVL. The MED12 mutations are different between IVL and uterine leiomyoma. These findings indicate that IVL is a unique entity and different from uterine leiomyoma.

Intravenous leiomyomatosis: molecular analysis of 17 cases.

Intravenous leiomyomatosis (IVL) is a rare smooth muscle tumour with a benign histology but with a quasi-malignant intravascular growth. In this study, we investigated the molecular alterations in 17 IVL cases composed of concurrent uterine leiomyoma (n=12), uterine IVL (n=17) and extra-uterine IVL (n=12). We found that eight tumours had a somatic MED12 mutation (c.130G>A, p.G44S, n=7; c.131G>C, p.G44A, n=1). The frequency of MED12 mutations was significantly higher in concurrent uterine leiomyoma (6/12, 50%) than in uterine (0/17, 0%) and extra-uterine IVL (2/12, 16.7%). The frequency of HMGA2 over-expression or MED12 low-expression was not significantly different among uterine leiomyoma, IVL and extra-uterine IVL (p>0.05). Short tandem repeat (STR) analysis indicated that one uterine and two extra-uterine IVL tumours from three patients were microsatellite instability positive (MSI+) whereas loss of heterozygosity (LOH) was found in one uterine leiomyoma, three uterine and three extra-uterine IVL tumours from five patients. LOH was more frequently seen in uterine/extra-uterine IVL tumours (6/20, 30%) than in the concurrent leiomyomas (1/7, 14.3%) (p<0.05). MED12 mutation, MSI and LOH were discordant between uterine and extra-uterine IVL in all patients. These findings suggest that IVL harbours distinct molecular pathogenesis from common uterine leiomyomas. Uterine IVL and extra-uterine tumours may represent an independent origin rather than uniclonal dissemination from a single tumour. Further investigations are warranted to explore the underlying key molecular events in the pathogenesis of IVL.

What is new in endothelial neoplasia?

The classification of vascular neoplasms continues to evolve as we accumulate more genetic and clinical data, particularly for rare tumor types. Because of tumor rarity, changes to classification schema, overlapping histologic features, and in some cases, lack of morphologic evidence of vasoformation, vascular neoplasms present a diagnostic challenge. Here, we discuss recent developments in our understanding of vascular tumors, with a detailed discussion of epithelioid hemangioma, tufted angioma, kaposiform hemangioendothelioma, composite hemangioendothelioma, pseudomyogenic hemangioendothelioma, epithelioid hemangioendothelioma, and angiosarcoma.