10 BULLETIN 1449, U. S. DEPARTMENT OF AGRICULTURE 
At times it is difficult to draw a sharp line between the hyper- 
plasias of connective tissue resulting from chronic inflammation as 
in chronic mastitis, and true fibromata. Diffuse hyperplasias of the 
viscera, which at times are inflammatory, are generally considered 
by most authorities as cases of diffuse fibrosis. 
Degeneration. — Serious infiltration and mucoid degeneration are 
often present in polypoid fibroids originating in the submucosa of 
the respiratory tract. Calcification and ossification have been re- 
ported but are rather rare. 
Nature. — Clinically, fibromas are benign neoplasms which do not 
give metastasis to internal organs unless they are combined with 
malignant growths. 
LIPOMA 
Definition. — Lipoma or fatty neoplasm is made up of adipose tis- 
sue, which it closely resembles in appearance and structure. It may 
be found in all domestic animals and is rather common. 
Seats. — Lipomas may grow wherever adipose tissue is normally 
present. The more common locations are the subcutaneous tissue in 
the region of the back, shoulders, breast, knees, inner surface of the 
thigh, the submucous tissue, and the subserous tissue of the 
mesentery, omentum, and peritoneal cavity. 
The less frequent places to find lipomas are the liver, kidney, 
lung, mammary gland, ovary, and uterus. 
Very rarely lipomas are found in the membrana nictitans in 
the horse and dog, also in the brain, arising from the blood vessels 
of either the pia mater or the dura mater. 
Macroscopic appearance. — Lipomas are usually single but fre- 
quently may be multiple. They are slow growing, at times rather 
small, but have been known to reach enormous size. They are 
usually smooth, encapsulated, and can be readily shelled out of the 
capsule, being well circumscribed from the surrounding tissue. 
Their shape may be round or oval while they are small, when de- 
veloped in the subcutaneous tissue, before they are subjected to 
pressure; but they become hemispherical or dome shaped when 
the pressure is from one side. When they become large the tension 
on the skin is sufficient to cause ulceration and even gangrene of the 
skin. Peritoneal lipomas in the omentum and intestines are often 
lobulated, especially in cattle, sheep, and hogs. The subserous in- 
testinal lipomas in cattle may also be pedunculated. When the 
pedicle is stout and elastic a loop of the intestine may wind around 
it and cause strangulation in the intestine. A more unusual shape 
of lipoma is the diffuse form. Under this heading may be men- 
tioned lipomatous elephantiasis. Lipomas may be firm or soft. If 
soft they are flabby. They are white or yellowish white in color, de- 
pending on the amount of connective tissue present and the- com- 
position of the fat. The fat of cattle, sheep, and hogs contains a 
higher percentage of stearin than of olein. In these animals the 
fat is whiter than in the horse. The fat of the horse contains more 
olein than stearin and is yellower and softer. The resistance varies 
according to the amount of connective tissue in the lipoma. 
Microscopic appearance. — The individual fat cells and the lobules 
in lipomas are larger than those in normal adipose tissues. The 
