TUMORS OF DOMESTIC ANIMALS 9 
brane, is dense, hard, white, and well defined from the muscle of 
the tongue. Fibroma in the tongue should be differentiated from 
actinomycosis, which often has collections of pus, sulphur-colored 
granules of colonies of actinomyces, and calcified areas. Among the 
rare locations for fibroma are the esophagus, stomach, intestine, 
mammary gland, lung, liver, kidney, and spleen. 
Structure. — According to the dense or loose arrangement of the 
fibrous-tissue bundles, fibromas are designated as soft or hard. They 
may be found in any part of the body where connective tissue is 
naturally present. A fibroma grows comparatively slowly and is 
encapsulated and usually poorly supplied with lymph and blood 
vessels. Exceptionally a fibroma may be very vascular, as the bleed- 
ing fibroids, which occur in man, but they are rare in animals. 
Fibromas are usually single, but they may be multiple, especially in 
animals. 
Macroscopic appearance of hard fibroma. — Hard fibroma is a nodu- 
lar or lobular firm growth, variable in consistence, circumscribed, 
and well defined from the surrounding tissues. It is generally 
encapsulated, light in color, slow growing, and usually small in size, 
but it may reach enormous size in the body cavities. It is somewhat 
dry, cutting with tough resistance like a tendon, and is glistening in 
appearance on the cut surface. 
Microscopic appearance of hard fibroma. — On microscopic exami- 
nation the bundles of fibers are found to be coarse in texture, wavy 
in their course, frequently interwoven, crossed, and interlaced in a 
most complex manner, and form whorls around the scanty blood 
vessels. Between the bundles a fair number of spindle-shaped cells 
are present. These cells are rather inconspicuous owing to the small 
amount of cytoplasm. The presence of elastic fibers in fibromas, 
although doubted by some observers, can be found in the denser 
forms of fibroma in animals. 
Structure of soft fibroma. — Soft fibroma, or fibroma molle, is soft 
in consistence, rich in cells, poor in fibrillar tissue, and is abundantly 
supplied with blood and lymph vessels. 
Macroscopic appearance of soft fibroma. — The color of fibroma 
molle is gray or grayish red, in contrast to the glistening white color 
of the hard fibroma. The shape may be nodular, often lobulated, 
and not infrequently polypoid or pedunculated when growing from 
a mucous membrane. 
Microscopic appearance of soft fibroma. — On microscopic appear- 
ance the connective-tissue bundles are seen to be more delicate and 
smaller in size and more loosely arranged than in hard fibromas. 
The cells are more numerous, possessing a considerable quantity of 
cytoplasm around the oval nuclei. They vary in shape and may be 
round, oval, spindle shaped, and irregular. Wandering cells, plasma 
cells, and leucocytes are often present. 
Combinations. — Fibromas may frequentty combine with other 
tumors, forming combinations in which the fibroma predominates, 
and the neoplasm is named by combining the two names, but naming 
the predominating tissue first, as in fibromyoma or in myofibroma. 
The more common combinations of fibroma with other tumors are 
fibromyoma, fibrolipoma, fibrochondroma, fibroosteoma, fibroangi- 
oma, fibroadenoma, fibropapilloma, etc. 
3262°— 26 2 
