Cancer

This is the only form of tumour which is of much practical importance, and it is of exceedingly frequent occurrence. From the statistics of a considerable number of observers it appears that cancer occurs more frequently in the stomach than in any other situation in the bod}7, the uterus being the next most frequent site.

The great frequency of cancer in the stomach is probably related to the fact that the epithelial structures of this organ are more exposed to various irritations than those of any other part of the body. Not only are there varieties of irritating foods, but the foods are liable, as we have seen, to decomposition, the products of which produce irritation. In cases of cancer there is very commonly a history of prolonged dyspepsia, perhaps from youth.

In this relation the simple ulcer may be again referred to. There have been cases observed in which cancer seemed to originate in the simple ulcer; but the simple ulcer is a disease mostly of youth, whereas cancer is a disease of middle life, the average age being fifty years. It is almost as if similar causes produced the simple ulcer in youth, and cancer in middle life.

In its Structure and Mode of growth, cancer of the stomach conforms to cancer elsewhere. It consists of epithelial masses contained in a stroma.

The epithelium originates from the epithelium of the mucous membrane or its glands, and sometimes it retains to a large extent the glandular characters (epithelial cancer). In growing, the cancerous tissue first infiltrates the mucous membrane and submucous tissue, producing thickenings of them. It also insinuates itself amongst the muscular bundles, frequently separating these and replacing them. It is not uncommon to find in the muscular coat almost isolated outposts, the cancerous tissue having only a narrow connection with the primary tumour. The cancer penetrates through the muscular coat to the subserous tissue, but does not commonly involve the surface of the peritoneum except in the case of colloid cancer (see under).

In their growth the cancerous processes irritate the tissues, and there is usually a considerable infiltration of round cells. In the more chronic infiltrating forms, there is a great new-formation of connective tissue, constituting scirrhous cancer.

As the cancer in its growth causes atrophy of the proper tissue, the affected part of the stomach comes to be composed more or less of cancer tissue. This is less calculated to resist the disintegrating action of the food and gastric juice than the normal mucous membrane, and hence Ulceration is a very frequent result. This will occur readily in the softer and more superficial cancers, and as these are the commoner, it is usually a prominent feature.

The Cancerous ulcer (Fig. 392) is usually considerably excavated, and there may be pieces of slough in its floor. Its edges are prominent, sometimes over-hanging, and they shade-off into the normal mucous membrane. In its central parts the ulcer may penetrate deeply sometimes through the coats of the stomach into neighbouring viscera, as the liver or transverse colon. On the other hand, the floor of the ulcer may be partially cicatrized. In slow-growing epithelial cancers the ulcer may be very large and, with its overhanging edges, may occupy a large part of the stomach.

Cancer of the stomach usually begins in the Pyloric region, although by no means always. In extending it not infrequently takes the form of a Ring around the pyloric region, and by its prominence and sometimes by the contraction of the ulcer may lead to obstruction.

Hypertrophy of the muscular coat of the stomach is present in most cases of cancer and is a striking feature in many. This arises from the fact that the cancer, by causing rigidity of the wall or by obstructing the pylorus, interferes with the peristaltic movement and so induces a compensatory hypertrophy of the muscle. Hence it is sometimes extreme in scirrhus and in pyloric cancers generally. The thickened muscular coat forms a somewhat stiff mantle, which on section has a pale glistening appearance, the trabeculae of the muscle being separated by partitions which run perpendicular to the surface.

The cancer affects surrounding parts both by Irritation and by Extension of the cancerous growth. The peritoneal surface is usually the seat of chronic inflammation, so that adhesions are present, sometimes producing great matting and entanglements around the stomach. The cancerous growth also sometimes extends by contiguity into organs with which adhesions have been contracted, chiefly the liver and transverse colon.

Fig. 392. - Ulcerated cancer of stomach. The central depression of the ulcer and the prominent infiltrated border are shown.

The Lymphatic glands are usually affected, in the first place those immediately in connection with the stomach at the lesser and greater curvatures, but also the prevertebral glands. A very frequent extension is to the Liver (which see) and a less frequent one to the Peritoneum.

As the secondary extension of cancers of the stomach and intestine presents many points in common, a special section is devoted to the subject further on.

The general characteristics of cancers of the stomach have been given above, and several forms have been referred to. It is possible to distinguish four different forms, which, however, are not absolutely separable.