Histologic and immunohistochemical characterization of hemangiomas in the skin of seven young horses.

The research paper examines the histological and immunochemical properties of benign vascular tumors removed from the skin of seven young horses. These properties were found to be similar to those evident during vascular development in a horse.

Research details

• The subjects of the study were seven young male horses of mixed breeds, all of them 16 months old or younger when the tumors were detected.
• Of the tumors studied, six were found on the extremities of the horses, and one was on the lip.
• Under a microscope, most of the tumors were seen to consist of cellular nodules of varying density, with a variable number of blood-filled spaces.
• The growth of these nodules caused the separation of existing skin structures and subcutaneous collagen, the protein that gives skin its structure and strength.
• Some tumors were found to contain, or primarily consist of, loosely arranged collections of veins and capillaries, separated by collagen within the dermis and subcutaneous tissues of the skin.

Findings on the cellular level

• Within the areas of nodule growth, the vascular walls were found to be composed of multiple layers. These layers were surrounded by strands of reticulin, a type of protein fiber, that align with the endothelium (the innermost lining of blood vessels) and adjacent pericytes (cells that surround endothelial cells), and also separate non-perivascular cells in the mass.
• Through immunohistochemical staining, factor-VIII-related antigen (a protein specific to blood cells) and Ulex europeus-1 lectin (a plant protein that can bind to specific carbohydrate molecules) were found to be restricted to the innermost layer of cells that surround vascular spaces, confirming their origination from blood vessels.
• The cells arranged around the endothelium and the cells not associated with vascular lumina were stained by the antibody to alpha-smooth muscle actin, confirming the presence of muscular cells in the structure of these nodules, as were the muscular compensations of larger vessels inside and outside of tumor nodules.
• The dermal structures and arrangement of cells within the tumors showed an established order, resembling the pattern seen during normal vascular development.

This research provides important insights into the histological and immunochemical properties of benign vascular tumors in young horses, opening the potential for improved diagnostic and therapeutic strategies.