Spleen - Angiectasis

Angiectasis consists of variable-size blood-filled spaces within the splenic parenchyma, lined by delicate to inapparent endothelium (Figure 1, arrow). Angiectasis in the spleen is usually a focal lesion that may be associated with an area of fibrosis or scarring (Figure 2, arrow) and is more common in mice. Congestion is often seen with angiectasis. It should be distinguished from hemorrhage, hemangioma, and hemangiosarcoma. Angiectasis can be distinguished from hemorrhage by the presence of endothelial cells lining discrete blood-filled spaces in angiectasis. The distinction between angiectasis and hemangioma is not always obvious. Hemangiomas tend to be well-circumscribed, unencapsulated masses composed of tightly packed, dilated vascular spaces. Each vascular space is enclosed and lined by a single layer of normal-appearing endothelial cells aligned on collagenous septa, which are usually thin, although some have broad collagenous stroma. Angiectasis does not usually present as a well-circumscribed mass; the dilated vascular channels often course irregularly through the hematopoietic tissue. Furthermore, the dilated vascular channels of angiectasis are not invasive and do not demonstrate endothelial cell atypia, which differentiates this lesion from hemangiosarcoma. Previous terms for angiectasis include "hemangiectasis," "hemangiectasia," "vasodilation," and "vasodilatation."