Immunohistochemical expression of vascular endothelial growth factor A (VEGF), and its receptors (VEGFR1, 2) in normal and pathologic conditions of the human thymus.

Vascular endothelial growth factor A (VEGF-A) is an angiogenic growth factor that is a primary stimulant of the vascularization of solid tumors. In the tumor microenvironment, an upregulation of both VEGF and its receptors occurs, leading to a high concentration of occupied receptors on tumor vascular endothelium. Also, VEGF is involved in the development of the normal vascular network of the thymus. Little is known about VEGF expression in normal and malignant thymic tissue. Our purpose was to study the pattern and localization of VEGF expression in benign conditions of the thymus and thymoma to determine a possible correlation with VEGF receptors VEGFR1, VEGFR2 and microvascular density. All cases were positive for VEGF and VEGFR1, 2 in the epithelial cells, in a cytoplasmic, granular pattern. In the normal thymus, there were positive epithelial cells with subcapsular distribution and Hassall's corpuscle epithelial cells. In acute thymic involution, the positive fields were correlated with dilation and stasis of blood vessels and lymphocyte depletion. Rare positive cells were found in other types of involution; the myasthenic thymus showed an intense and diffuse reaction in lymphoid follicles of the medulla. A strong reaction for VEGF was observed in type B3 thymomas in neoplastic epithelial cells, normal endothelial cells, plasma within the blood vessels and focally in the stroma adjacent to the tumor. Receptors for VEGF were positive in neoplastic epithelial cells and endothelium. We hypothesized that VEGF acts as an immunoregulatory factor in the normal thymus and as proangiogenic and autocrine factor in thymomas.

Morphologic and histochemical changes in the skin of patients with scleroderma.

BACKGROUND: Systemic sclerosis or scleroderma is a rare collagen disease, characterized by insufficient angiogenesis. Few data are available about the morphologic and histochemical peculiarities of the skin in these patients with this condition. The purpose of the present work was to evaluate the histochemical aspects of sclerodermic skin, obtained through biopsy of the typical lesions from the forearm skin. PATIENTS AND METHODS: The study was conducted on 31 patients, from which skin biopsies were obtained, after informed consent. The specimens were fixed in buffer formalin, embedded in paraffin and processed for staining with HE, Masson, orcein, Gordon-Sweet silver staining, and alcian blue-safranin, in order to identify elastic fibers, reticular fibers, glycosaminoglycans and mast cells. Results are partially similar to other studies: the constant depletion of elastic fibers in the papillary dermis and disorders of the network in the reticular dermis, such as their absence in the skin blood vessels walls. The reticular fibers were absent in the papillary dermis, the reaction in the reticular dermis structure was variable from a case to another. The staining with Alcian blue-Safranin proved that there is a gathering of glycosaminoglycans in the superficial papillary dermis, the heterogeneity of collagen fibers and the decrease of mast cells in the dermis.

Simultaneous demonstration of mast cells and blood vessels by the combined method CD34--alcian blue-safranin in lip tumors.

The aim of the study was to evaluate the mast cell-blood vessel relationship using double staining CD34/AAS. Sections from 14 cases with lip tumors have been stained with Hematoxylin-Eosin. On additional sections from each case, we highlighted blood vessels by immunohistochemistry for CD34 antigen using the method LSAB2-HRP/DAB, followed by alcian blue-safranin stain for mast cells. We quantified the density, distribution and the mast cell types as well as the correlation with the number of blood vessels. All cases have been positive for both staining. We observed a significant correlation between the number of vessels and the mast cells (p = 0.003). In one case, we observed the mast cells stained with safranin (red), the vascular density being less than the mast cells density. Our results confirmed the data from the literature with respect to the large number of mast cells observed in the malignant tumors. The increased vascular density together with the mast cell density suggests a correlation between these two elements in the tumor angiogenesis, possibly though the VEGF secretion. The CD34/AAS stain is a quick and simple method and it allows an optimal correlation between the number of mast cells and blood vessels on the same section. The type of mast cells correlated with microvessel density is a powerful argument towards the involvement of the mast cells in the tumor angiogenesis of the malignances of the lips.