In attacking these growths the vascular and bloody area may be met just about their margins, the bloodvessels expanding as they arrive at the tumor, and sometimes bleeding extensively. Under most circumstances, however, this hemorrhage can be controlled by packing or by operating at a greater distance from the circumference of the growth.
Metastasis in sarcoma is common, dissemination occurring mainly along the veins, as these growths connect with the venous channels and permit of easy detachment of fragments, which are then carried along as emboli. These emboli pass naturally to the right side of the heart, and thence to the lungs, where it is most common to find secondary growths, except in areas emptying into the portal veins, in which case the liver will be the most common site. Sarcomas are destitute of lymphatics, and dissemination does not occur through these channels.
Infiltration is also a common phenomenon with these growths. This is generally seen in muscular tissue, particularly with growths proceeding from the periosteum and projecting into it.
Sarcomas, like other tumors, tend to grow along the lines of least resistance. Hence processes of these tumors will insinuate themselves into fissures and interspaces, and penetrate perhaps even into the cavities, from which it is hazardous or impossible to remove them. Thus, sarcomas springing from the head of a rib have been known to extend through an intervertebral foramen and give rise to an intraspinal tumor, causing fatal pressure.
Secondary changes are usually seen in sarcomas, the most frequent being hemorrhage. Myxomatous degeneration is also frequent, and gives rise to cystic conditions. Calcification is common, particularly in the slowly growing tumors which arise from bone. Upon the other hand, necrosis (i. e., ulceration) is common in growths which project upon the surface or into any of the open cavities of the body. Ulceration here is growth at a rate faster than nutrition will justify, and gangrene is to be regarded as a failure to supply sufficient blood. It may also mean infection, of which it is a usual expression.
Tumors of this character, which luxuriate upon reaching the surface, and bleed easily upon the slightest touch, were formerly known as fungus hematodes. The name may be preserved for the sake of convenience, but should be held to mean, in almost every instance, a rapidly growing round-cell sarcoma.
Sarcoma is common in the lower animals, particularly so in horses—most common in those of gray color. It is met with also in cows and various other domestic and undomesticated animals.
Myxoma.
—The myxomas are composed of mucous tissue, whose best-known normal representative is the Whartonian jelly of the umbilical cord. True myxoma should be distinguished from myxomatous degeneration, which occurs frequently in cartilage, fibrous tissue, and sarcoma, and which brings about a similar condition of affairs, though of essentially different origin. Myxomas appear under the following forms:
1. Polypi.