Infantile hemangioma is a proliferation of LYVE-1-negative blood endothelial cells without lymphatic competence

Benign and low-grade superficial endothelial cell neoplasms in the molecular era

Vascular tumors are the most common mesenchymal neoplasms of the skin and subcutis, and they encompass a heterogeneous group with diverse clinical, histological, and molecular features, as well as biological behavior. Over the past two decades, molecular studies have enabled the identification of pathogenic recurrent genetic alterations that can be used as additional data points to support the correct classification of these lesions. The purpose of this review is to summarize the available data related to superficially located benign and low-grade vascular neoplasms and to highlight recent molecular advances with the role of surrogate immunohistochemistry to target pathogenic proteins as diagnostic biomarkers.

Integrin β4 Is an Effective and Efficient Marker in Synchronously Highlighting Lymphatic and Blood Vascular Invasion, and Perineural Aggression in Malignancy

Lymphovascular invasion (LVI) and perineural invasion (PNI) are 2 important pathologic parameters and need to be accurately assessed in multiple malignancies. Integrin β4, a member of the integrin family, has been reported to be positively expressed in vascular endothelia, peripheral nerves, and a collection of epithelia. However, little is known about the effectiveness of β4 immunostaining on the recognition of LVI and PNI. Herein, we explored the applicability of β4 immunostaining in stomach, thyroid, and breast cancers. Parallel immunostaining of D2-40, CD34, and S-100 was performed as controls for lymphatic endothelia, vascular endothelia, and neural fibers, respectively. The results demonstrated that β4 concurrently stained the lymphatic and vascular endothelia, and the peripheral nerves. Both LVI and PNI were clearly and accurately outlined by β4 immunostaining. β4 was also expressed in the majority of tumor cells, enabling recognition of LVI and PNI encroached by small tumor clusters. In contrast to D2-40 and CD34, β4 staining was not observed in stromal cells, and therefore it facilitated differentiation between the shrinkage cleft and LVI. According to our results, β4 staining strikingly increased the diagnostic accuracy and interobserver concordance for LVI and PNI compared with hematoxylin and eosin staining alone. Finally, the applicability of β4 was confirmed in 9 other types of malignancies, including cancers of the colon, prostate, esophagus, lung, kidney, uterus, tongue, bladder, and liver. Collectively, β4 is a reliable marker for synchronous detection and diagnosis of LVI and PNI.

Restricted Range of Motion and a Cold Upper Extremity in a Two-Year-Old Boy: Kaposiform Hemangioendothelioma of the Bone and the Brachial Plexus: A Case Report

CASE

We report a case of kaposiform hemangioendothelioma (KHE) of the scapula in a 2-year-old boy with motor and sensory abnormalities of the left upper extremity, suggesting brachial plexus involvement. The locally invasive nature prevented resection; sirolimus therapy resulted in improvement of the motor and sensory impairment, as well as decreased tumor size on imaging.

CONCLUSION

Osseous infiltration of KHE is known to occur, but its primary presentation in bone without skin involvement is rare and diagnostically challenging. Awareness of rare presentations of KHE, along with accurate histopathologic interpretation, is important to achieve a diagnosis and to differentiate KHE from more common vascular lesions (e.g., infantile hemangioma). Sirolimus therapy is emerging as a promising treatment for unresectable KHE.

A hydrogel-endothelial cell implant mimics infantile hemangioma: modulation by survivin and the Hippo pathway

Microvascular endothelial cells cultured in three-dimensional hydrogel scaffolds form a network of microvessel structures when implanted subcutaneously in mice, inosculate with host vessels, and over time remodel into large ectatic vascular structures resembling hemangiomas. When compared with infantile hemangiomas, similarities were noted, including a temporal progression from a morphological appearance of a proliferative phase to the appearance of an involuted phase, mimicking the proliferative and involutional phases of infantile hemangioma. Consistent with the progression of a proliferative phase to an involuted phase, both the murine implants and human biopsy tissue exhibit reduced expression of Ajuba, YAP, and Survivin labeling as they progressed over time. Significant numbers of CD45+, CD11b+, Mac3+ mononuclear cells were found at the 2-week time point in our implant model that correlated with the presence of CD45+, CD68+ mononuclear cells observed in biopsies of human proliferative-phase hemangiomas. At the 4-week time point in our implant model, only small numbers of CD45+ cells were detected, which again correlated with our findings of significantly diminished CD45+, CD68+ mononuclear cells in human involutional-phase hemangiomas. The demonstration of mononuclear cell infiltration transiently in the proliferative phase of these lesions suggests that the vascular proliferation and/or regression may be driven in part by an immune response. Gross and microscopic morphological appearances of human proliferative and involutional hemangiomas and our implant model correlate well with each other as do the expression levels of Hippo pathway components (Ajuba and YAP) and Survivin and correlate with proliferation in these entities. Inhibitors of Survivin and Ajuba (which we have demonstrated to inhibit proliferation and increase apoptosis in murine hemangioendothelioma cell tissue culture) may have potential as other beneficial treatments for proliferating infantile hemangiomas. This implant model may have potential as a modest through-put screen for testing and development of therapeutics targeted at the proliferative phase of infantile hemangiomas, reducing the subsequent postinvolutional scarring or deformities sometimes associated with these lesions.

Immunohistochemical endothelial markers: a review

A relatively large number of new endothelial markers that can assist in the diagnosis and classification of endothelial and vascular neoplasms have become available over the past few years. The expression of these markers, however, differs considerably among the various tumors. A selection of markers that have potential diagnostic utility or are of current interest among pathologists are reviewed and compared with some of the more traditional markers that have been employed in diagnostic pathology.

Prox1 transcription factor as a marker for vascular tumors-evaluation of 314 vascular endothelial and 1086 nonvascular tumors

Prox1, a transcription factor important in the regulation and maintenance of the lymphatic endothelial phenotype, is consistently expressed in lymphangiomas and Kaposi sarcoma and has also been reported in Kaposiform hemangioendothelioma. However, information on its distribution in vascular tumors, such as angiosarcoma, is limited. In this study, we examined selected normal tissues and 314 vascular endothelial and 1086 nonvascular tumors to get an insight into the biology of these tumors and on potential diagnostic use of Prox1 as an immunohistochemical marker. In adult tissues, Prox1 was essentially restricted to lymphatic endothelia, with expression in subsets of pancreatic and gastrointestinal epithelia. However, it was also detected in embryonic liver and heart. Prox1 was consistently expressed in lymphangiomas, venous hemangiomas, Kaposi sarcoma, in endothelia of spindle cell hemangioma, Kaposiform hemangioendothelioma, and retiform hemangioendothelioma, and in half of epithelioid hemangioendotheliomas. It was present in most cutaneous angiosarcomas from different sites but was less commonly expressed in deep soft tissue and visceral angiosarcomas. In contrast, Prox1 was generally absent in capillary and cavernous hemangiomas. In positive hemangiomas and angiosarcomas it was coexpressed with podoplanin, another marker of the lymphatic endothelial phenotype. There was an inverse correlation with CD34 expression. The expression in mesenchymal nonendothelial neoplasm was limited. Prox1 was detected in 5 of 27 synovial sarcomas, specifically in the epithelia of biphasic tumors. Four of 16 Ewing sarcomas and 5 of 15 paragangliomas were also positive. All melanomas and undifferentiated sarcomas were negative. Among epithelial neoplasms, Prox1 was detected in 18 of 38 colonic carcinomas and 10 of 15 cholangiocarcinomas and in a minority of pulmonary, prostatic, and endometrial adenocarcinomas. The common Prox1 expression in angiosarcoma and its rare presence in nonvascular mesenchymal tumors make this marker suitable for the diagnosis of angiosarcoma and Kaposi sarcoma. However, the presence of Prox1 in some malignant epithelial tumors necessitates caution in applying Prox1 as a marker for vascular tumors. Common Prox1 expression in angiosarcoma may reflect the lymphatic endothelial phenotype in these tumors. Its patterns of expression in hemangiomas and angiosarcoma may be diagnostically useful and offer a new parameter in the biological classification of vascular tumors.

Solitary hepatic lymphangioma: report of a case

A 52-year-old woman presented with upper abdominal pain. Abdominal ultrasonography showed a 4-cm well-defined mass containing solid and cystic components in segment IV of the liver, and contrast-enhanced T1-weighted magnetic resonance imaging revealed heterogeneous enhancement within the tumor, indicating a solid or fibrous component. There were no cystic lesions in any other organs. A partial hepatectomy was performed, based on a preoperative diagnosis of sclerosing hemangioma and biliary cystadenoma or cystadenocarcinoma. Pathologically, the tumor appeared to be a multilocular and cystic lesion lined by attenuated endothelial- like cells with no atypia. Immunohistochemistry demonstrated the endothelial-like cells to be positive for the lymphatic-specific markers D2-40, LYVE-1, and Prox-1, which proved helpful for confirming the diagnosis as solitary hepatic lymphangioma. This case is presented with details of the pathologic and radiologic findings, because solitary hepatic lymphangioma is an extremely rare tumor and no previous reports have provided details of the immunohistochemical characteristics.

Solitary hepatic lymphangioma: report of a case

A 52-year-old woman presented with upper abdominal pain. Abdominal ultrasonography showed a 4-cm well-defined mass containing solid and cystic components in segment IV of the liver, and contrast-enhanced T1-weighted magnetic resonance imaging revealed heterogeneous enhancement within the tumor, indicating a solid or fibrous component. There were no cystic lesions in any other organs. A partial hepatectomy was performed, based on a preoperative diagnosis of sclerosing hemangioma and biliary cystadenoma or cystadenocarcinoma. Pathologically, the tumor appeared to be a multilocular and cystic lesion lined by attenuated endothelial- like cells with no atypia. Immunohistochemistry demonstrated the endothelial-like cells to be positive for the lymphatic-specific markers D2-40, LYVE-1, and Prox-1, which proved helpful for confirming the diagnosis as solitary hepatic lymphangioma. This case is presented with details of the pathologic and radiologic findings, because solitary hepatic lymphangioma is an extremely rare tumor and no previous reports have provided details of the immunohistochemical characteristics.

Characterization of anti-podoplanin monoclonal antibodies: critical epitopes for neutralizing the interaction between podoplanin and CLEC-2

Podoplanin (Aggrus) is a mucin-type sialoglycoprotein that is known as a useful marker for lymphatic endothelium and tumor-initiating cells (TICs). Interaction between podoplanin and C-type lectin-like receptor-2 (CLEC-2) is reported to be critical for podoplanin-induced platelet aggregation and cancer metastasis. Recently, several anti-human podoplanin antibodies have been created; however, these anti-podoplanin antibodies have not been well characterized. Five anti-podoplanin antibodies (NZ-1, D2-40, AB3, 18H5, and a rabbit polyclonal antibody) were investigated using ELISA, Western blot, and flow cytometry with synthesized podoplanin peptides and deletion mutants of recombinant podoplanin. The epitope of NZ-1 is platelet aggregation-stimulating (PLAG) domain-2/3; the epitope of D2-40, AB3, and 18H5 is PLAG1/2. The epitopes of D2-40 and AB3 are quite similar, although 18H5 is different from D2-40 and AB3. Using flow cytometric analysis, NZ-1 partially inhibited the interaction between podoplanin and CLEC-2, although other antibodies did not. In conclusion, the two most frequently used anti-podoplanin antibodies, D2-40 and AB3, have similar properties, although several studies have reported differences. NZ-1 neutralizes the interaction between podoplanin and CLEC-2, which may lead to the development of therapeutic antibodies against podoplanin-dependent cancer metastasis.

Pathogenesis of infantile haemangioma: new molecular and cellular insights

Infantile haemangioma is the most common tumour of infancy, yet the origin of these lesions remains controversial and the predictable life cycle is poorly understood. Much new information on infantile haemangiomas has emerged over the past decade, but experts continue to debate fundamental features, including cell of origin, nonrandom distribution, and mechanisms regulating the sometimes explosive growth and slow involution. The development of useful laboratory models has been difficult, in turn restricting the development of treatment options available to the clinician. Despite this, new research and creative thinking has spawned several hypotheses on the origin of these tumours and their interesting clinical behaviour, including suggestions of an intrinsic defect in local endothelial cells, a contribution of circulating endothelial progenitors or haemangioblasts, embolisation of shed placental cells and developmental field defects. While no single hypothesis seems to describe all features of infantile haemangioma, continued research seeks to integrate these ideas, create a better understanding of these important tumours and bring new treatments to the clinic.