Tumour

TUMOUR, a term applied, from the earliest period of medical literature, to any swelling of which the nature and origin were un known. Consequently a heterogeneous collection of swellings was described as tumours, including such diverse conditions as an abscess, a tuberculous gland, the enlarged spleen of malaria or a cancer. With the progress of bacteriology and the improved tech nique of histology it became necessary to separate these various "swellings" into groups : Inflammatory or Infective Swellings; (2) Swellings due to Hypertrophy; (3) Cysts; (4) Spontaneous Tumours, or New-growths. By general consent the term "tumour" is now restricted to the last group. However, for the sake of com pleteness and because clinically it is not always easy to diagnose the true nature of a swelling, it is necessary to touch briefly on the distinguishing features of the first three groups.

I. Inflammatory or Infective Swellings.—These have cer tain characteristics which separate them sharply from other classes of swelling. In the first place they are due to the irritative action of some micro-organism. Inflammation due to microbial action always follows a typical course. First, numbers of wander ing cells derived from the blood, the lymph or the connective tissues collect at the site of irritation, and these, with the coag ulable serum poured out from the blood vessels produce the hard painful swelling with which every one is familiar. The mass may gradually subside or it may soften in the centre so that an abscess results. Thus an inflammatory swelling may be solid or fluid according to circumstances. The common inflammatory bacteria— staphylococcus and streptococcus—cause suppuration in the ma jority of cases, but a few organisms such as the different varieties of streptothrix, Treponema pallida, and the tubercle bacillus, set up an inflammation so chronic that it does not usually end in the formation of pus, but rather in the development of a hard, solid mass of very slow growth, that may persist for months or even years.

To the naked eye and to touch these solid inflammatory swellings may closely simulate the spontaneous tumours and, often, the two have been confused, but a microscopical examination will correct the mistake in nearly every case. For the minute structure of in

fective swellings, whatever their situation, is almost identical; they consist merely of an irregular collection of inflammatory cells; and this of itself is sufficient to mark them off from the group of tumours proper. To this statement there is one excep tion, for a form of malignant tumour, known as a sarcoma, may bear a very deceptive likeness to an inflammatory swelling.

2. Swellings due to Hypertrophy.

A tissue or organ is said to be hypertrophied when it is increased in size but remains approximately normal in structure. The most familiar example is the hypertrophy of the skeletal muscles that follows increased use, or the hypertrophy of the heart muscle which helps to com pensate for faulty action of the valves. But neither of these constitutes a hypertrophic swelling. For an instance of this we must turn to the enlargement of the spleen that occurs in malaria and certain forms of anaemia, of the thyroid gland in some varieties of goitre, and of the lymphatic glands in Hodgkin's disease. In each of these conditions there is an increase of ap parently normal tissue, and from a microscopical examination of the hypertrophied organ it is difficult to say that it is unhealthy.

3. Cysts.

A cyst may be defined as a collection of fluid sur rounded by a wall or capsule. The nature of the fluid varies ac cording to the site and origin of the cyst ; the cyst-wall is usually composed of a tough layer of fibrous tissue. Cysts arise by the dilatation of a pre-existing space with fluid, the central degenera tion and liquefaction of a solid mass, as in some varieties of cancer, the disintegration of blood clot as in some cysts of the brain, the natural growth of some parasites, e.g., hydatid cysts. When the cyst-wall is tensely stretched by the pressure of the fluid within it, a cyst may easily be mistaken for a solid tumour.