Cellular haemangioma. Light and electron microscopic studies of two cases

Durable response of intracranial cellular hemangioma to bevacizumab and temozolomide

Cellular hemangioma is a subtype of hemangioma that is associated with cellular immaturity and the potential for recurrence. Intracranial location of these lesions is extremely rare, and definitive treatment often requires radical neurosurgical resection. The authors report a case of a 12-year-old boy with a subtemporal cellular hemangioma. He underwent gross-total resection of the tumor, but within 1.5 months the tumor recurred, necessitating a second resection. Because of its proximity to vascular structures, only subtotal resection was possible. Repeat MRI 1 month after the second surgery showed significant tumor recurrence. Given the tumor's demonstrated capacity for recurrence and its proximity to the vein of Labbé and sigmoid sinus, further resection was not indicated. In an effort to limit radiation therapy for this young patient, treatment with bevacizumab and temozolomide was chosen and achieved a complete response that has proven durable for 36 months after cessation of therapy. This is the first report of the successful use of chemotherapy to treat an intracranial hemangioma, a rare condition with limited therapeutic options.

Pericytes from infantile hemangioma display proangiogenic properties and dysregulated angiopoietin-1

OBJECTIVE

Infantile hemangioma (IH) is a rapidly growing vascular tumor affecting newborns. It is composed of immature endothelial cells and pericytes that proliferate into a disorganized mass of blood vessels. We isolated pericytes from IH (Hem-pericytes) to test our hypothesis that Hem-pericytes are unable to stabilize blood vessels.

METHODS AND RESULTS

We injected pericytes in vivo, in combination with endothelial cells, and found that Hem-pericytes formed more microvessels compared with control retinal pericytes. We, thereby, analyzed proangiogenic properties of the Hem-pericytes. They grew fast in vitro, and were unable to stabilize endothelial cell growth and migration, and expressed high levels of vascular endothelial growth factor-A compared with retinal pericytes. Hem-pericytes from proliferating phase IH showed lower contractility in vitro, compared with Hem-pericytes from the involuting phase and retinal pericytes. Consistent with a diminished ability to stabilize endothelium, angiopoietin 1 was reduced in Hem-pericytes compared with retinal pericytes. Normal retinal pericytes in which angiopoietin 1 was silenced produced conditioned medium that stimulated endothelial cell proliferation and migration.

CONCLUSIONS

We report the first successful isolation of patient-derived pericytes from IH tissue. Hem-pericytes exhibited proangiogenic properties and low levels of angiopoietin 1, consistent with a diminished ability to stabilize blood vessels in IH.

Infantile hemangiomas: A review

Infantile hemangiomas (IH) are the most common eyelid and orbital tumors of childhood. Although they are considered benign lesions that have a generally self-limited course, in the periocular region, they have the potential to cause amblyopia, strabismus, and severe disfigurement. The decision for treatment can be a source of anxiety for patients, parents, and physicians alike. There are numerous treatment modalities, including emerging therapies that may make treatment safer and more effective than ever before. This review discusses our current understanding of this disease, its management, and future therapies.

Hemostatic and hematological abnormalities in gain-of-function fps/fes transgenic mice are associated with the angiogenic phenotype

The Fps/Fes tyrosine kinase has been implicated in the regulation of hematopoiesis and inflammation. Mice expressing an activated variant of Fps/Fes (MFps) encoded by a gain-of-function mutant transgenic fps/fes allele (fps(MF)) exhibited hematological phenotypes, which suggested that Fps/Fes can direct hematopoietic lineage output. These mice also displayed marked hypervascularity and multifocal-hemangiomas which implicated this kinase in the regulation of angiogenesis. Here we explored the potential involvement of Fps/Fes in the regulation of hemostasis through effects on blood cells and the vascular endothelium. Hematological parameters of fps(MF) mice were characterized by peripheral blood analysis, histology, and transmission electron microscopy. Hemostasis parameters and platelet functions were assessed by flow cytometry and measurements of activated partial thromboplastin time, prothrombin time, thrombin clot time, platelet aggregation, bleeding times and in vitro fibrinolytic assays. Hematological and morphological analyses showed that fps(MF) mice displayed mild thrombocytopenia, anemia, red cell abnormalities and numerous hemostatic defects, including hypofibrinogenemia, hyper-fibrinolysis, impaired whole blood aggregation and a mild bleeding diathesis. fps(MF) mice displayed a complex array of hemostatic perturbations which are reminiscent of hemostatic disorders such as disseminated intravascular coagulation (DIC) and of hemangioma-associated pathologies such as Kasabach-Merritt phenomenon (KMS). These studies suggest that Fps/Fes influences both angiogenic and hemostatic function through regulatory effects on the endothelium.

Lobular capillary hemangioma of the oral mucosa: clinicopathological study of 43 cases with a special reference to immunohistochemical characterization of the vascular elements

Clinical and histopathological features were investigated in 43 cases of oral lobular capillary hemangiomas (LCH) with a special reference to characteristics of the vascular elements. The lesions affected females more than males by a ratio of 1:1.5. Average age of the patients was 52.7 years. The lesions involved the gingiva (n = 15), the tongue (n = 13), the labial mucosa (n = 10) and other sites. The lesions appeared usually as a pedunculated mass with ulceration; size of the lesions was up to 15 mm. Histologically, a lobular area and an ulcerative area were distinguished. The density of vessels was about 1045/mm2 and 160/mm2 in the lobular and ulcerative areas, respectively. The average diameter of the vascular lumen was 9.1 5.6 mm (range: 2.8-42.0 mm) and 18.8 20.9 mm (range: 5.6-139.7 mm) in the lobular and ulcerative areas, respectively. In the lobular area, most of the vessels had an inner layer of endothelial cells showing positive reaction for von Willebrand factor (vWF) and CD34, as well as an outer layer of mesenchymal cells showing positive reaction for alpha-smooth muscle actin (ASMA). However, in the ulcerative area, there was a variety of types of vessels consisting of various proportions of both endothelial and ASMA-positive perivascular mesenchymal cells. These results indicate that most of the vascular elements in the lobular area resemble more pericapillary microvascular segments than they do capillaries. Thus, the authors propose the term 'lobular pericapillary hemangioma' to represent this type of lesion.

GLUT1: a newly discovered immunohistochemical marker for juvenile hemangiomas

Juvenile hemangiomas are common, benign vascular tumors of infancy. These lesions enlarge rapidly through cellular hyperplasia during the first year of life and then involute over several years. Distinctive histopathologic features of hemangiomas diminish during this evolution, and differentiation from vascular malformations becomes increasingly difficult. This distinction has important therapeutic implications, as juvenile hemangiomas differ from malformations in natural history and in potential for recurrence. We report here that high endothelial immunoreactivity for the erythrocyte-type glucose transporter protein GLUT1 is a specific feature of juvenile hemangiomas during all phases of these lesions. In a retrospective study, we found intense endothelial GLUT1 immunoreactivity, involving more than 50% of lesional microvessels, in 97% (139 of 143) of juvenile hemangiomas from patients aged 1 month to 11 years. No endothelial GLUT1 immunoreactivity was found in any of 66 vascular malformations (17 arteriovenous, 33 venous, 11 lymphatic, and 5 port-wine) from patients aged 5 days to 75 years, or in any of 20 pyogenic granulomas or 7 granulation tissue specimens. Abundant Ki-67 positivity in these latter lesions established that GLUT1 expression does not simply reflect mitotically active endothelium. Focal GLUT1 immunoreactivity was found in 3 of 12 angiosarcomas, but not in any of 5 hemangioendotheliomas (epithelioid or infantile kaposiform). These findings establish GLUT1 immunoreactivity as a highly selective and diagnostically useful marker for juvenile hemangiomas. Because high levels of endothelial GLUT1 expression in normal tissue are restricted to microvessels with blood-tissue barrier function, these findings also have implications for the molecular and developmental pathogenic mechanisms of juvenile hemangiomas.

Angiogenic histogenesis of stromal cells in hemangioblastoma: ultrastructural and immunohistochemical study

Controversy regarding the origin of characteristic stromal cells (SC) is responsible for the placement of hemangioblastoma as a single entity in the category of "tumors of uncertain histogenesis" in the current WHO classification of brain tumors. This subclassification of hemangioblastoma is, to a large extent, a consequence of a remarkable antigenic heterogeneity of SC demonstrated in many, often contradictory immunohistochemical studies. In contrast, most of the electron microscopic studies demonstrated a number of features indicating angiogenic nature of SC and, therefore, hemangioblastoma. This study reevaluated the histogenesis of SC, applying immunohistochemistry as well as electron microscopy and immunoelectron microscopy. Immunohistochemical studies confirmed most of the previous results indicating a very frequent expression of vimentin, S-100 protein, neuron-specific enolase, and cytokeratins. SC were less commonly immunoreactive for desmin, factor XIIIa, and Ricinus communis lectin receptors, and only occasionally for factor VIII and Ulex europeus lectin. They were negative for other markers of endothelial, neuronal, glial, neuroendocrine, and smooth muscle differentiation. Approximately 1% of SC showed Ki67 immunoreactivity, indicating their slight proliferative activity, consistent with the benign nature of the tumor. In contrast to the inconclusive results of the immunohistochemistry, electron microscopy demonstrated a clear relationship of SC to endothelial cells, smooth muscle cells, and pericytes. Occasional SC were found within the vascular lumina. SC often showed intracellular caveolae consistent with the formation of early capillary lumina. Moreover, occasional SC contained small Weibel-Palade bodies positive for factor VIII in immunoelectron microscopy. SC represent a heterogeneous population of abnormally differentiating mesenchymal cells of angiogenic lineage, with some morphological features of endothelium, pericytes, and smooth muscle cells. Occurrence of SC in hemangioblastoma could be related to a limited ability of angioformative stromal cells to develop an architecture of capillary lumina integrated with the vascular network of the tumor. Hemangioblastoma should be reclassified and included together with other vascular tumors of the central nervous system.

Cellular markers that distinguish the phases of hemangioma during infancy and childhood

Hemangiomas, localized tumors of blood vessels, appear in approximately 10-12% of Caucasian infants. These lesions are characterized by a rapid proliferation of capillaries for the first year (proliferating phase), followed by slow, inevitable, regression of the tumor over the ensuing 1-5 yr (involuting phase), and continual improvement until 6-12 yr of age (involuted phase). To delineate the clinically observed growth phases of hemangiomas at a cellular level, we undertook an immunohistochemical analysis using nine independent markers. The proliferating phase was defined by high expression of proliferating cell nuclear antigen, type IV collagenase, and vascular endothelial growth factor. Elevated expression of the tissue inhibitor of metalloproteinase, TIMP 1, an inhibitor of new blood vessel formation, was observed exclusively in the involuting phase. High expression of basic fibroblast growth factor (bFGF) and urokinase was present in the proliferating and involuting phases. There was coexpression of bFGF and endothelial phenotypic markers CD31 and von Willebrand factor in the proliferating phase. These results provide an objective basis for staging hemangiomas and may be used to evaluate pharmacological agents, such as corticosteroids and interferon alfa-2a, which accelerate regression of hemangiomas. By contrast, vascular malformations do not express proliferating cell nuclear antigen, vascular endothelial growth factor, bFGF, type IV collagenase, and urokinase. These data demonstrate immunohistochemical differences between proliferating hemangiomas and vascular malformations which reflect the biological distinctions between these vascular lesions.

Infantile (juvenile) capillary hemangioma: a tumor of heterogeneous cellular elements

Infantile (juvenile) capillary hemangiomas are vascular neoplasms which can appear quite infiltrative histologically and are characterized by cords of cells with areas of marked cellularity. While vessels can be distinguished in most cases, there are many cells which do not appear to be endothelial in origin. We labeled 5 such cases with antibodies directed against factor VIII-related antigen, CD34, alpha actin, factor XIIIa and PC-10. Anti-factor VIII-related antigen labeled all endothelial cells and did not label cells away from vessels. Anti-CD34 recognized similar cells and also stained a subset of interstitial cells. Anti-alpha muscle defined pericytes and stained few interstitial cells and none of the endothelial cells. Many of the interstitial spindled and cuboidal cells stained strongly with anti-factor XIIIa. The majority of the mitotic activity was concentrated in the interstitial cells. These observations lend support to the concept that infantile (juvenile) capillary hemangioma is a tumor of primitive cells with capabilities for differentiating toward endothelial cells and pericytes. It is not clear whether a similar stem cell population gives rise to dermal dendrocytes, or whether these represent an immune response to the neoplasm.

Ultrastructural study of pseudo-Kaposi's sarcoma (Bluefarb-Stewart type)

An ultrastructural study of the skin lesion of a young patient affected by pseudo-Kaposi's sarcoma of the Bluefarb-Stewart type (BSS) is reported. The neoplasm consisted of a proliferation of vascular structures mostly consisting of a solid bud of endothelial cells surrounded by a thinned and polystratified basement membrane and several pericytes. Both endothelial cells and pericytes were of normal ultrastructural appearance. Intervascular "stromal" cells were few and morphologically identified as macrophages and/or phagocytic fibroblasts. Masses of hemosiderin were detected outside the cells and in the macrophages, endothelial cells, and pericytes. Intracytoplasmatic crystalloid inclusions similar to those found in fetal endothelium and hemangiomas were observed in a few endothelial cells. These findings are different from those of previously reported cases of pseudo-Kaposi's sarcoma and may be helpful in distinguishing Kaposi's sarcoma from BSS. The role of immunodeficiency in the onset of BSS is discussed.

Endothelial cell crystalloids in newborn human foreskin

This study describes the presence of crystalline inclusions in the endothelial cells of foreskins. They were found in 9 normal full-term newborn infants, without maternal medication or complication during pregnancy and delivery. These cytoplasmic crystalloids occurred in 10% of endothelial cells of small blood vessels. The diameter of the inclusions ranged from 0.3 to 1.5 micron and they appeared as round, oval, hexagonal or irregular polygonal in shape. These inclusions were surrounded by a triple membrane and their contents demonstrated granular, homogeneous and crystalloid-like material with a regular periodicity of dense and less dense layers measuring about 20-25 nm. Similar crystalloids in the endothelial cells were observed in the normal upper lip skin of a 6-week-old girl, although they were present in much smaller numbers than in foreskin. No endothelial inclusions were found in normal skin taken from 11 body areas in 29 patients aged 2.5 to 56 years. The nature and function of these cytoplasmic crystalloids are unknown.

Adult cutaneous hemangiomas are composed of nonreplicating endothelial cells

Thirty-four human "cherry" dermal hemangiomas were studied by electron microscopy, immunohistochemistry, and cell culture to assess the neoplastic nature of these lesions. Electron microscopy of nine hemangiomas revealed a pronounced thickening of the basement membrane (0.6 to 14 micron) in 93% of the total 158 vascular structures examined within the lesions. This increase was caused mainly by multiple layers of basal lamina, which were irregular in outline and frequently associated with pericytes. Basement membrane changes were present both in the periphery of the hemangiomas, as well as in the center of the lesions. Immature vessels could not be identified and mitoses were absent in all endothelial cells. Using an immunohistochemical marker (Ki67) specific for proliferating cells in G2 and S phases, positive staining was not found in the endothelial cells lining the hemangiomatous vessels, whereas basal epidermal keratinocytes in the same preparations and cultured microvascular endothelial cells expressed the antigen. Endothelial cells of nine hemangiomas did not stain with an activation-related antibody (E12) specific for endothelial cells. When endothelial cells from 14 hemangiomas were isolated and cultured under conditions that support the growth of normal human skin microvascular endothelial cells, the cells of hemangiomatous origin failed to grow. We conclude that the adult hemangiomas may not be true neoplasms, but a tissue overgrowth composed of mature vessels resembling dermal venules, lined by endothelial cells with virtually no turnover.

An ultrastructural study of mast cell interactions in hemangiomas

Hemangiomas, the most common tumors of infancy, are characterized by a postnatal period of rapid growth, followed by a phase of gradual involution. The proliferative phase is characterized by increased numbers of endothelial and mast cells and thickened basement membrane. Ultrastructural analysis of hemangiomas in the late proliferative phase showed that mast cells had numerous fingerlike processes aligned parallel to the outer lamina of the thickened basement membranes surrounding the vessels and to the surfaces of opposing cell membranes. We found evidence of different types of interactions between mast cells and adjacent connective tissue cells (fibroblasts, macrophages, multinucleated giant cells, and plasma cells) in the perivascular regions of the lesions. Intercellular contacts were observed in areas where these mast cell processes were in close association to the opposing cell membrane. Areas of membrane fusions were seen between cell types. Coated vesicles and pinocytotic vesicles were present along the periphery of cells adjacent to mast cells. Occasionally, cytoplasmic bridges were found between mast cells and fibroblasts. These ultrastructural findings suggest the proliferation and involution of hemangiomas are determined by interactions between the various types of cells found in the lesions.

Two- and three-dimensional ultrastructural observations of angiogenesis in juvenile hemangioma

Two- and three-dimensional electron microscopic observations by a serial sectioning method revealed endothelial sprouts with intracytoplasmic vacuolization in rapidly growing human juvenile hemangioma. A large vacuole bounded by a single unit membrane was enclosed in the cytoplasm and on the inner aspect of the vacuolar membrane several short microvilli were demonstrated. These appearances have not been reported before. The presence of microvilli in the vacuole indicates that the endothelium has reached the point of differentiation when a vascular lumen forms. In the cytoplasm adjacent to the vacuolar membrane, a significant number of 7 to 10 nm microfilaments were identified. These intracytoplasmic microfilaments are assumed to play a mechanical role in the development of the cytoplasmic vacuole and/or the sprout. The formation of a vacuole observed in the endothelial sprout is similar to the findings of Sabin (1920) by light microscopy in endothelial sprouts in the blood island of the chick embryo. The active endothelial sprout in juvenile hemangiomas is considered to be at least partially responsible for the capillary proliferation and enlargement of the tumor.

Ultrastructure of mast cells in growing and involuting stages of hemangiomas

Mast cells from 11 patients with growing strawberry (capillary) hemangiomas and cellular hemangiomas and from ten patients with involuting stages of strawberry hemangiomas were investigated electron microscopically. Two types of mast cells were evident: numerous elongated, fibroblastic cells and a few round, classic cells. The mast cells in growing hemangiomas contained many small, simple-type granules in various stages of development. It is possible that, owing to the immaturity of these granules, mast cells have different, probably weaker, functional activities. Mast cells in involuting stages of hemangiomas were filled primarily with compound-type granules, showing typical parallel, concentric lamellae or crystalloid structures, which were similar to the mature mast cells in normal skin.