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Left paraspinal tumour.
Kaposiform hemagioendothelioma is a rare locally aggressive vascular tumour often found in skin, deep soft tissue, and bone in a pediatric population. Sections show fibrovascular and myxoid tissue containing a vascular lesion with a nodular and lobular architecture. The nodules comprise a mixture of spindle cells, capillary-like spaces and occasional dilated thin-walled vessels. Capillaries form focal glomeruloid-like structures, and slitlike capillaries are also seen, particularly in association with spindle cells. The cells are bland with evenly dispersed chromatin and inconspicuous nucleoli, and mitoses are inconspicuous. Occasional fibrin thrombi are identified within vessels and hemosiderosis is also seen.
Immunohistochemical staining for CD31, CD34, D2-40, Glut-1 and SMA have been performed. These reveal positivity in the lesional cells for CD31 and CD34, and focal positivity for D2-40 in the slit-like capillaries (but negative in the glomeruyloid structures). SMA highlights pericytes. Glut-1 is negative in lesional endothelium.