TUMORS OF DOMESTIC ANIMALS 19 
Degeneration. — Degenerative changes are frequently found in the 
gliomas and lead to fatty degeneration, followed by softening, and 
often result in the formation of cysts. 
ANGIOMA 
Definition. — Angiomas are neoplasms composed of vascular tissue. 
If formed of blood vessels they are called " hemangiomas," when 
formed of lymph vessels they are called " lymphangiomas." They 
have a relatively small amount of supporting tissue. In either case 
there must be new formation or proliferation of the vessels. The dis- 
tention alone of preexisting vessels, without proliferation, does not 
constitute angioma, any more than the alteration in the blood pres- 
sure of a local venous obstruction. Neither do capillary telan- 
giectases, which can take place in local areas of the liver by a partial 
obstruction of a branch of the hepatic vein; nor do hemorrhoids, 
which are instances of compensatory dilatation of vessels, constitute 
angiomas. 
Hemangiomas or angiomas proper are usually composed of pro- 
liferating and dilated vessels, arteries, veins, or capillaries and are 
classified as capillary angioma or angioma telangiectaticum. If the 
blood spaces are large, irregular, and intercommunicating they are 
designated as the cavernous type. Usually there may be gradations 
of these two types where the vascular channels are larger than capil- 
laries but not large enough to be called venous spaces. 
Seats. — In man there is found a superficial form of skin angioma 
that is rarely seen in domestic animals. This is probably due to the 
larger amount of pigment and the thickness of the skin in animals. 
However, the finding of this type of angioma at the root of the tail 
in dogs and horses has been reported. A comparatively common 
form of angioma, which is congenital, is the angioma simplex or the 
capillary form of angioma found in the skin of man about the face 
and known as birthmarks. 
Structure. — Angiomas consist of capillaries with preformed, im- 
perfect, thin-walled vessels resembling veins. The presence of these 
vessels conveys a bright-red color to the skin, but its surface is not 
raised. Rarely the walls of the vessels are thickened and tortuous 
in their course, superficially situated, forming palpitating groups of 
vessels in the scalp, which suggest in appearance a bunch of creeping 
earthworms. This form is described by some writers as angioma 
plexiform, angioma racemosum, or circoid aneurism. 
Cavernous angioma. — Cavernous angioma consists of vascular 
channels which are dilated to the extent of large, communicating 
spaces lined with endothelial cells. The spaces are supported by 
interstitial connective tissue. These spaces are venous channels and 
suggest the structure of the corpus cavernosum. When situated in 
the skin they appear as dark red to almost bluish, extensive blotches 
that are commonly known as " port- wine stains," vascular nevi. or 
blue warts. Cavernous angiomas, like the angioma simplex or telan- 
giectaticum, occur in the skin and also in internal organs, of which 
the liver is the most frequent seat in man. It is also very common in 
the liver of cattle and hogs, but may also be found in other domestic 
animals. Less frequently angioma is found in the kidney, spleen, in- 
testine, bladder, muscles, bone marrow, brain, dura mater, and very 
rarely in the spinal cord. 
