The aim of this study is to compare and analyze the histological differences between vascular and mucosal hemorrhoids, two structurally different types of hemorrhoids. Methods: Internal hemorrhoidal tissue samples were fixed in 10% Formalin solution, and coronal sections included 10-mm proximal and 5-mm distal of the dentate line. Routine Masson-Trichrome and H&E were performed to evaluate the thickness of the mucosa and changes in the structure and the densities of submucosal vessels,

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... e tissue, and muscle. Results: Compared with the corresponding tissues of mucosal hemorrhoids, the submucosal connective tissue and perivascular connective tissue of vascular hemorrhoids showed a loosened density, severe fragmentation, and an irregular arrangement. The submucosal vascular dilatation was more frequent and more severe in vascular hemorrhoids, but the number of vessels between both types of hemorrhoids did not show much difference. Hypertrophy and regular arrangement of the submucosal muscles were observed more frequently in the mucosal than in the vascular hemorrhoids. Conclusion: Compared to mucosal hemorrhoids, vascular hemorrhoids showed augmented damage in submucosal connective tissue and intense dilatation of vessels with a thinner mucosa. On the other hand, compared to vascular hemorrhoids, mucosal hemorrhoids showed hypertrophy of submucosal muscle and relatively minor alterations in vessels with a thicker mucosa. These histological differences may provide the basis for different etiologies between vascular and mucosal hemorrhoids.