A distinction between angiectasis and hemangioma should be attempted, although the distinction 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.
Angiectasis has been observed in rodents with severe loss of hematopoietic tissue. It is also observed as a nonspecific finding or in association with inflammation, neoplasia, or vascular/cardiovascular disorders (e.g., thrombi, congestive heart failure).
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