i. Neoplasms. Normally, the body grows by multiplication of its cells. At first,
in the embryo, these cells are all alike or undifferentiated. However, as they multiply,
they come under the influence of certain factors and take on different forms and
different functions to make up the different tissues, organs, and systems of the body
(that is, they become differentiated). This growth and differentiation is a slow,
methodical, controlled process. However, some cells may not differentiate entirely, but
for some unknown reasons, retain varying degrees of undifferentiation, break free of
their growth control, and form a new growth (neoplasm) or tumor. Tumors cause
disease by interfering with the function of normal cells, tissues, and organs. They may
cause pressure on an organ so that its normal cells are destroyed or its blood supply is
shut off. A tumor may fill the cavity of an organ so that the organ wall cannot contract
properly. The tumor may also use up the nutritive materials taken into the body so that
there is not enough for the normal tissues. Tumors are of two types: benign and
malignant.
(1) Benign. These are more slowly growing, the cells are more
differentiated, the tumor is well separated from the surrounding tissues by its capsule,
and can usually be completely removed surgically.
(2) Malignant. These are more rapidly growing with very little growth
control, and the cells are more primitive or undifferentiated. The cells of the tumor
infiltrate or grow between the normal tissue cells, and are much more difficult to remove
surgically. Because of this, the malignant tumor tends to recur and tends to
metastasize or spread via the blood and the lymph vessels. The common term for
malignant tumors is cancer. The medical profession speaks of carcinoma when the
malignant tumor arises from tissue that covers the surface of the body, lines a hollow
structure, or forms glands, and sarcoma when the malignant tumor arises from any
other tissue in the body such as fatty, muscular, bony, or fibrous tissue.
j. Idiopathic (Unknown) Causes. There are many diseases of known etiology.
The affected organ and effective treatment are often known, however, the cause and
the mechanism through which the disease disrupts the body's functions remain
unknown.
Section VI. TREATMENT OF DISEASE AND INJURY
2-18. INTRODUCTION
Patients who have disease or injury must be properly diagnosed and treated. The
physician is responsible for these functions; however, the physician may delegate the
accomplishment of some of the treatments to other members of the Army Medical
Department (that is, physicians' assistants and physical therapists). In general, all types
of treatment may be classified as either preventive or corrective.
MD0804
2-22