Fine structure of senile angiomas of human skin

Hemangioma rubi no couro cabeludo

O hemangioma rubi (HR) é dermatose de origem vascular extremamente freqüente, acometendo mais de 75% da população acima de 70 anos de idade. Em geral compõe-se de lesões múltiplas,localizadas predominantemente no alto do tronco e braços. Clinicamente é caracterizado por lesões que variam desde máculas puntiformes até lesões papulosas com cinco milímetros de diâmetro. As mais novas são vermelhas, em tons vivos, e as mais antigas podem ser azuladas. O HR é de etiologia desconhecida. Histologicamente chama atenção uma neoformação de vasos capilares, que se tornam dilatados e com fenestrações em suas paredes. A membrana basal está muito espessada e existe abundante estroma de colágeno entre os vasos. O presente trabalho demonstra a alta incidência do HR no couro cabeludo Em amostra de 171 pacientes, sendo 85 homens e 86 mulheres, o autor observou que 123 deles (72%) tinham HR no couro cabeludo, localização em que o HR nunca foi descrito na literatura.

Increase in types IV and VI collagen in cherry haemangiomas

The capillaries in cherry haemangiomas show perivascular hyalinized sheaths. In order to clarify the nature of this sheath material, the extracellular matrix of cherry haemangiomas from 20 normal volunteers (age range 30-64 years) was investigated using immunohistochemical and electronmicroscopical methods. Antibodies against collagen types III, IV and VI and laminin were used. Hyaluronic acid was visualized using the hyaluronic acid binding region of the cartilage proteoglycan as ligand. Electronmicroscopically, the sheaths contained multilaminated basement membrane-like material, collagen fibres 20-25 nm thick with a periodicity of 67 nm and broad-banded aggregates with a periodicity of 100 nm (zebra bodies or fibrous long-spacing fibres). Immunohistochemically, type IV collagen was stained throughout the whole sheath material. Staining for laminin was more confined to the endothelial side of the sheath. Intense staining for type III collagen and hyaluronic acid was found in the connective tissue of the subpapillary layer and between the cherry haemangioma capillaries. Much weaker staining for type III collagen and no staining for hyaluronic acid were found invariably in an area 4-10 microns thick directly around the capillaries. Both sheath material and intercapillary connective tissue of the haemangiomas showed pronounced staining for collagen type VI. Immunogold staining revealed that type VI collagen was localized to microfibrils 5-6 nm thick and to the broad-banded aggregates with 100 nm periodicity. These findings further underline the assumption that the broad-banded aggregates consist of type VI collagen.

The laminate capillary and its wall of multiple basement membranes

Cutaneous telangiectatic vessels from two cases of unilateral dermatomal superficial telangiectasia were shown under electron microscopy to be venular capillaries with thick walls composed of multiple basement membranes. We suggest that this special capillary structure, seen in a variety of telangiectatic and disease states, should be called the 'laminate capillary'.

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.

Active proliferation of telangiectases in skin of patients with progressive systemic sclerosis (PSS)

The labeling index of endothelial cells as measured by in vitro autoradiography with 3H-thymidine and the electron microscopic structure of microvessels were studied in telangiectases. The telangiectases of eight patients with progressive systemic sclerosis (PSS) were compared with the cherry angiomas of six healthy controls subjects. The ultrastructural features of telangiectases were similar in the two groups and were characteristic of capillaries and postcapillary venules of the dermis, with multilayering of the vascular basement membrane. However, a significant difference existed between these two groups in an autoradiographic study: in PSS telangiectases, the average labeling index was 5.9%, whereas in cherry angiomas it was around 0.8%. Thus, the telangiectases in PSS are structures with accelerated endothelial proliferation, as are the other endothelial cells of microvessels anywhere in dermis in this disease. However, the great heterogeneity of the labeling index (varying from 0.5% to 27%) must be emphasized in telangiectases.

Ultrastructural study of hemangiomas. 4. Cavernous hemangioma of the liver

Seven cases of cavernous hemangioma of the liver found accidentally at autopsy were studied by electron microscope. The structures of the hemangioma consisted of capillaries and the intervening stromal cells. The endothelial cells contained pinocytotic vesicles, scattered ribosomes, rough endoplasmic reticulum, and Golgi apparatus. A distinct basement membrane was present beneath the endothelial cells, and multilaminated arrangement of the basement membrane was sometimes observed beneath the endothelial cells. The endothelial cells also contained numerous cytoplasmic filaments, but contained sparse specific endothelial granules. The internal elastic lamina was hardly seen at all in the hemangioma. The stromal cells showed typical smooth muscle cells, modified smooth muscle cells, and fibroblast-like cells. Elastic tissue as well as collagen fibers was present within the intervening stroma. Neither adventitia nor nerve fibers were found in the cavernous hemangioma. It is thought that cavernous hemangioma of the liver may be of a hamartomatous nature.

Localized vascular regression during limb morphogenesis in the chicken embryo: II. Morphological changes in the vasculature

The regression of blood vessels in the distal wing bud of chicken embryos from stages 19 to 31 was examined by light and electron microscopy. The vessels were double-labelled by an injection of Monastral blue B (MB) to label the regressing endothelial cells, followed 6-48 hours later with an injection of India ink which marked the lumens of patent vessels. Prior to stage 26 the vessels contained only India ink since the endothelial cells were not phagocytic at this stage. Vessels at stage 26 or later were often double-labelled, with MB sequestered in the endothelial cell cytoplasm and India ink in the vessel lumens. After stage 27 cells not associated with lumens, but labelled with MB, were observed in areas undergoing vascular regression. Ultrastructural changes in the endothelial cells as the vessels regressed included formation of luminal and abluminal processes, long complex junctions, and vacuoles containing MB. In many involuting vessels the endothelial cells appeared normal even though the lumens were collapsed. Occasionally, isolated pyknotic cells were observed in regions that had been previously vascularized. At stage 31 cells in the developing cartilage had vacuoles containing MB. Our study suggests that blood vessels may disappear from the prechondrogenic zone of the distal wing bud by several mechanisms. These could include a type of cell death that does not elicit a cellular infiltrate, migration of the endothelial cells away from vascularized regions, and/or transdifferentiation into cells that resembled chondrocytes.

Ultrastructure and three-dimensional reconstruction of several macular and papular telangiectases

Eight types of telangiectases were studied by light and electron microscopy and by 3-dimensional reconstruction from photomicrographs. Five were macular: mat telangiectasia of scleroderma, generalized essential telangiectasia, nevus flammeus, and 2 macular types not previously described. Three were papular: cherry angioma, angiokeratoma (Fabry), and angiokeratoma (Fordyce). The macular telangiectases were produced by dilatation of postcapillary venules of the upper horizontal plexus. There was no evidence of neovascularization or vascular malformation. The walls of the dilated venules were thickened by the peripheral deposition of basement membrane-like material admixed with reticulin fibers. The ultrastructure and configuration of the papular telangiectases were different. The cherry angioma was produced by spherical and tubular dilatations of capillary loops in dermal papillae. Each abnormally dilated loop was connected to the neighboring loop or loops by tortuous vascular channels. The vessels in the upper horizontal plexus were not involved. Ultrastructurally, the cherry angiomas were composed of both venous capillaries and postcapillary venules whose walls were thickened in a manner identical to that observed in the macular telangiectases. The angiokeratomas of Fabry and Fordyce were also produced by vascular abnormalities predominantly involving the dermal papillae. Ultrastructurally these vessels were similar to the small collecting veins which are normally found at the dermal-subcutaneous interface. Thus, the papular telangiectases also arose by alterations of the existing microvasculature rather than by proliferation of new vessels with random anastomoses. Reconstruction of the upper horizontal plexus from normal skin showed an undulating network of arterioles and their accompanying postcapillary venules. A 3-layered plexus arranged as venules, arterioles, and venules was not found.

Patterns of regeneration in vessels of human diseased muscle and skin. An ultrastructural study

Regenerating vessels from 36 muscle biopsies and 12 skin biopsies pertaining to patients with the clinical and histological diagnosis of dermatomyositis-polymyositis and other inflammatory myopathies were described ultrastructurally. The following characteristics of vascular regeneration were encountered: a) alternation of thin and thick endothelial cells, b) superimposed segments of endothelial cytoplasm with formation of twisted intercellular junctions, c) long and complex intraluminal endothelial projections, d) discontinuous and porous perivascular basement lamina or multilaminated basement lamina. Some vessels featured only two or three of the mentioned characteristics. Endothelial fenestrations were occasionally encountered in the skin capillaries and were an exception in the muscle capillaries. In the skin there were aspects suggesting that intercalation of perivascular cells in the regenerating endothelial wall may occur. Most capillaries were in the final stage of regeneration.

Ultrastructural aspects of normolipidemic xanthomatosis

Electron microscopic aspects in ten cases of normolipidemic cutaneous xanthomatosis have been investigated. Two additional types IV and V hyperlipoproteinaemic xanthomatosis have also been included. Ultrastructural findings in all cases were similar. Abundant histiocytic cells with numerous intracytoplasmic lipid vacuoles, lysosomes, and myelin-figures, were the striking features. Moreover, in older lesions microfilaments and lipid vacuoles were found in some fibroblastic cells, as well as long space collagen around them. In some specimens we observed: giant multinucleated histiocytic cells, crystalline cleft-like spaces in histiocytes and some mastocytes with lipidic crystals in the extracellular space, as well as lipid vacuoles in Schwann cells, endothelial cells and pericytes. Rod-shaped tubulated bodies were found in some endothelial cells, with multiple basal vascular laminae. In xantelasma palpebrarum and in disseminate plane xanthoma the histiocytary foamy cells adopted a perivascular arrangement, as in hyperlipoproteinemic xanthomatosis. We concluded that ultrastructural aspects of different xanthomatosis are fairly similar as a consequence of the large amount of intracytoplasmic lipids accumulated in xanthomatosus cells. In xanthelasma palpebrarum and in disseminated plane xanthoma this cell phase is reached by similar pathways to those for hyperlipoproteinemic xanthomatosis, whilst in xanthoma disseminatum and juvenile xanthogranuloma the pathways seem to be different. A classification of normolipidemic xanthomatosis is also provided.

Ultrastructural observations on the capillaries of human thyroid tumours

Ultrastructure of the capillaries of malignant and benign thyroid tumours has been examined. The material consisted of biopsies from six cases of thyroid papillary carcinoma, one case of follicular (foetal type) adenoma and six cases of nodular adenomatous goitre. In the group of nodular adenomatous goitre and in the follicular adenoma, the capillary wall was made up of fenestrated endothelium similar to that of capillaries of normal human thyroid. The fenestrae occupied a large area of the endothelial wall. Micro- and macropinocytotic vesicles were frequent in the endothelial cytoplasm. In the thyroid carcinomas the papillary structures always contained numerous capillaries with fenestrated endothelium. The microfollicular area and the solid tumoral areas of the papillary carcinoma showed occasional capillaries with fenestrated endothelium, but many capillaries were lined with continuous endothelium. The capillaries in all the specimens were surrounded externally by a continuous basement membrane which was frequently bilaminate or multilaminate. This study indicates that capillaries with fenestrated endothelium are characteristic of thyroid tumours which arise from follicular cells.

Fine structure of multiple neonatal haemangioendothelioma of the liver

This paper discusses the fine structure of multiple haemangioendothelioma of the liver. There have been no previous reports of electron microscopic studies of this tumour, which was found to be composed of young capillaries continuous in type and varying in calibre. The capillaries were lined by actively proliferating, immature endothelial cells with pericytes forming an integral part of the tumour. Their morphological characteristics indicated intensive protein production. The authors suggest that the active pericytes play a role in the production of reticular fibres of the tumour. Following corticosteroid therapy, regression of tumour nodules occurred in this case in the interval between surgery and autopsy. This was confirmed by histological studies. The results seem to support the hypothesis that actively proliferating, young endothelial cells show an increased sensitivity to corticosteroids.

Ultrastructure of human dermal blood vessels with special reference to the endothelial filaments

The ultrastructure of endothelial cytoplasmic filaments of small blood vessels from the human dermis has been described. The material consisted of biopsies from normal abdominal and thoracic skin and also from the skin of patients with urticaria pigmentosa. Most vessels were surrounded by multiple layers of basal lamina and corresponded to the small venules of the subpapillary dermis. The wall of many vessels was composed by endothelial cells with clear cytoplasm which was rich in filaments and by endothelial cells with a dense cytoplasm which was poor in filaments. Some vessels had walls composed of clear endothelial cells only. The filaments varied in diameter between 80-120 A. Curling, recoiling and whorling of cytoplasmic filaments were obvious in endothelial cells of contracted vessels. Bulging of endothelial nuclei and nuclear indentations were seen in the skin lesion of urticaria pigmentosa. The possibility that the clear endothelial cells which are rich in filaments may be more actively involved in contraction than the dense cells, is discussed.

Ultrastructure of the human dermal microcirculation: the horizontal plexus of the papillary dermis

Electron microscopy was used to define the ultrastructure of the various segments of the human cutaneous microcirculation in normal forearem skin. The organization of the vessels in the horizontal plexus of the papillary dermis was reconstructed from 1-mum plasticembedded sections. Ultrathin sections were taken at 10- to 20-mum intervals over a distance of 450 mum. Arterioles were followed through the capillary bed to their venous connections. Terminal arterioles, arterial and venous capillaries, and postcapillary venules were identified on the basis of size, cellular composition of their walls, and their relationship to the other segments of the microvascular bed. The arterial segments were characterized by a homogeneous basement membrane and the venous segments by a multilaminated basement membrane. The elastic lamina in the arterioles was a discontinuous layer which gradually disappeared from the arteriolar wall to form an external sheath just before the arteriole connected with the arterial capillary segment. The vascular walls varied from 1 to 5 mum in all of the segments of the microvascular bed. Criteria are proposed for identifying the various segments of the microcirculation so that their roles in dermatoses and vascular malformations can be evaluated.

Angiosarcoma of the skin. A clinicopathologic and fine structural study

A study of ten cutaneous angiosarcomas is presented. These tumors characteristically involve the scalp or face of elderly individuals, where they present as bluish or violaceous plaques and nodules. They have a marked tendency for local spread in surface and depth, and a third of them eventually give rise to distant metastases, particularly to cervical lymph nodes and lung. Microscopically, angiomatous areas of freely anastomosing channels lined by atypical endothelial cells are seen alternating with Kaposi-like spindle cell areas and undifferentiated foci. By electron microscopy, the tumor cells are seen to have all the features of endothelial cells, including pinocytotic vesicles, tubulated bodies, and in one case closed fenestrations. They also exhibit a cytoplasmic specialization here interpreted as the intracellular formation of a vascular lumen. Pericytes and cells resembling smooth muscle cells are also present. In the differential diagnosis this entity has to be distinguished from other clinical types of angiosarcoma of the skin and from a number of benign and malignant conditions. It is suggested that surgery be used for solitary, well circumscribed tumors and radiation therapy for tumors that either are multicentric or have ill defined margins.