Distribution of lymphatic vessel network in normal urinary bladder

OBJECTIVES The lymphatic vessel endothelial hyaluronan receptor (LYVE-1) is a novel lymphatic vessel marker that is expressed on lymph vessel endothelial cells. The objective of this study was to determine the LYVE-1 expression patterns in normal urothelium and to compose the geometric topography of the lymphatic network. METHODS Immunohistochemical staining for LYVE-1 and von Willebrand factor was performed to assess the differences in the distribution of lymphatic vessels between the components in the urinary bladder. The sizes of the individual lymphatic vessels were categorized as small, medium, and large. To compare the lymphatic density (counts per square millimeter), the number of lymphatic vessels of the five random areas was counted in each specimen. RESULTS LYVE-1 expression and the lymphatic density of the muscularis propria were significantly greater than those of other layers, including the epithelium, lamina propria, perivesical fat, and serosa (P < 0.0001). The size of the lymphatic vessels in the muscularis propria was significantly smaller than that in the other layers (P < 0.0001). The greatest distribution of the lymphatic vessels was identified in the border areas consisting of the lamina propria and muscular propria or the muscular propria and adventitia, including the perivesical fat and serosa. CONCLUSIONS We have developed a new type of color geometric topography to accurately exhibit the distribution of that complex network. Lymphatic vessels, although small, are predominately distributed in the muscularis propria in the normal urothelium compared with that in the other layers. The LYVE-1 antibody was a useful specific marker for the illustration of the lymphatic vessel in conventional paraffin-embedded specimens of the urinary bladder.