Cancer of the stomach is a relatively common lesion with a discouragingly low curability rate at the present time. Not only is it difficult to detect or diagnose in the localized or asymptomatic stage, but when it assumes the form of an ulcerating lesion, it is difficult or impossible to distinguish clinically from benign gastric ulcer. Nevertheless, its frequency requires a knowledge of its characteristics. Furthermore, there is good reason to believe that, with more widespread application of presently available screening and diagnostic methods, the over-all picture could be improved.

Epidemiology. Incidence

Mortality

Rates And Ratios

Age

Trend Past Ten Years

Geographic Distribution

There is a wide variation in the mortality of stomach cancer in different countries of the world (Table 9). The highest recorded rates are those for Japan, where the mortality for both men and women is five times that for white men and women in the United States. Similarly high rates have been reported for Chile (male, 69.7 per 100,000 and female 47.6 per 100,000 for 1954-1955) and for Iceland (men and women combined 65 for 1940-1949). In Japan and Iceland approximately 50% of all male cancer deaths and 35% of all female cancer deaths are due to gastric carcinoma as contrasted with the United States figures of 8.5% and 6%, respectively. Environmental factors of possible etiologic significance include differences in diet, methods of preserving and cooking food, soil constituents, etc.

Table 9. Stomach (Annual Mortality Rates Per 100,000, 1956-1957)

•Age-adjusted on combined population of forty-six countries in 1950. *From Segi, M.: Cancer Mortality for Selected Sites in Twenty-Four Countries (1950-1957), Sendai, Japan, 1960, Tohoku University School of Medicine.

Etiology

Although the incidence of stomach cancer can often be clearly related to certain measurable changes in gastric physiology and the presence of specific benign conditions such as pernicious anemia (see below), little is known about the basic etiology of this lesion.

Attempts to relate the occurrence of the disease to smoking, drinking, and dietary factors, occupational industrial exposures, etc. have been unrewarding thus far.

Heredity may play a role, but its nature and magnitude are yet to be defined. Studies have been reported which estimate a four times greater than average frequency among relatives of patients with gastric cancer. Most observers would probably regard this estimate as too high, but an increased risk of some degree may very likely be present, possibly on the basis of inherited characteristics of gastric physiology. The latter, plus an increased susceptibility to as yet undefined environmental influences, probably accounts for the apparent concentration of the disease in certain families.

Blood group A has been found by some to be characteristic of a disproportionate number of persons with stomach cancer, again stressing the potential role of hereditary influences. This relationship has not been confirmed by all workers, however.

The possible role of environmental factors in gastric cancer is emphasized by certain obvious epidemiologic clues:

1. Its extraordinary variation in incidence in certain countries

2. Its recent and continuing decrease in this country by almost one third in ten years.

3. Its concentration in males by a ratio of 2:1

Such clues suggest that at least a portion of the incidence of stomach cancer may be related to environmental factors at play in certain groups, particularly among males. Whatever they may be, their effect in the United States appears to be diminishing with every passing decade.

Pathology

Approximately 90 to 95% of all cancer that occurs in the stomach can be classified as adenocarcinoma, although the degree of differentiation may vary widely. Our principal concern is with this variety.

Classification

Numerous classifications of stomach cancer have been advanced, many of them leaning heavily on microscopic and other details seldom available to the clinician except in retrospect.

From the practitioner's standpoint, the best classification is one which refects certain features of gross pathology, x-ray appearance, and clinical findings.

FUNGATING-22.7%

Growth predominantly toward the lumen Seldom ulcer picture

Prognosis dependent on degree of Invasion at tho base but often fairly good

PENETRATING-27.5%

Growth predominantly away from tho lumen May show ulcer picture Intermediate prognosis

SPREADING-SUPERFICIAL-8.3%

Growth predominantly lateral rather than toward tho lumen or serosa

May bo confined to tho mucosa or submucosa May bo called in situ May show ulcor picture Prognosis variable; may bo good

SPREADING-LINITIS PLASTICA-4.5%

Growth predominantly lateral rather than toward lumen or serosa

Mucosa may look relatively normal; ovon biopsy may bo negative

Originates deep in tho mucosa, muscularis, or submucosa

Infiltrates and thickens tho entire stomach wall Prognosis poor

No special type accounts for 37% of stomach lesions.

Fig. 59. Classification of stomach cancer according to Stout.

The classification by A. P. Stout will be used here (Fig. 59).

It must be remembered that the relative concentration of the various types will depend on the material studied. If the cases reported are from a surgical (i.e., operable or at least operated upon) series, the percentages will vary significantly from those derived from autopsies. Surgical practice at the institution reporting also plays a role.

The fact that over one third of cases of stomach cancer cannot be specifically classified in any of the three major categories reflects the fact that the lesions are often quite far advanced at the time of diagnosis.