Page 571 - Textbook of Pathology, 6th Edition

true phenotypic features of smooth muscle cells, neural cells 555
or Schwann cells. They are uncommon but as compared to
other sites in the GIT, are most common in the stomach. Their
behaviour is generally benign but may be recurrent,
aggressive or even metastasis may occur.

C. MALIGNANT TUMOURS
Gastric Carcinoma

INCIDENCE. Carcinoma of the stomach comprises more
than 90% of all gastric malignancies and is the leading cause
of cancer-related deaths in countries where its incidence is
high. The highest incidence is between 4th to 6th decades of
life and is twice more common in men than in women.
ETIOLOGY. A number of etiologic factors have been
implicated in causation of gastric cancer. These are as under:
1. H. pylori infection. H. pylori infection of the stomach is Figure 20.15 Distribution of gastric carcinoma in the anatomical
an important risk factor for the development of gastric cancer. subdivisions of the stomach. The serial numbers in the figure indicate
the order of frequency of occurrence of gastric cancer.
Epidemiologic studies throughout world have shown that a
seropositivity with H. pylori is associated with 3 to 6 times
higher risk of development of gastric cancer. It may be common in individuals with blood group O). A germ line
mentioned here that similar association of H. pylori infection mutation in E-cadherin gene inherited as a autosomal
exists with gastric lymphomas (MALT type) as well. dominant pattern has been linked to higher incidence of
occult gastric cancer in younger individuals.
2. Dietary factors. Epidemiological studies suggest that die-
tary factors are most significant in the etiology of gastric 6. Pre-malignant changes in the gastric mucosa. There are CHAPTER 20
cancer. The evidences in support of this are multifold: some conditions of gastric mucosa which have increased risk
i) Occurrence of gastric cancer in the region of gastric canal to development of gastric cancer:
(i.e. along the lesser curvature and the pyloric antrum) where i) Hypo- or achlorhydria in atrophic gastritis of gastric
irritating foods exert their maximum effect. mucosa with intestinal metaplasia.
ii) Populations consuming certain foodstuffs have high risk ii) Adenomatous (neoplastic) polyps of the stomach.
of developing gastric cancer e.g. ingestion of smoked foods, iii) Chronic gastric ulcer (ulcer-cancer), and its association
high intake of salt, pickled raw vegetables, high intake of with achlorhydria.
carcinogens as nitrates in foods and drinking water, nitrites iv) Stump carcinoma in patients who have undergone partial
as preservatives for certain meats etc. However, intake of gastrectomy.
green leafy vegetables, citrus fruits and animal fats has been MORPHOLOGIC FEATURES. Gastric carcinoma is most
reported to have protective role in gastric cancer. commonly located in the region of gastric canal (prepyloric The Gastrointestinal Tract
iii) Tobacco smoke, tobacco juice and consumption of alcohol region) formed by lesser curvature, pylorus and antrum.
have all been shown to have carcinogenic effect on gastric Other less common locations are the body, cardia and
mucosa.
fundus (Fig. 20.15).
3. Geographical factors. There are geographic variations Pathogenetically, a sequential evolution of all gastric
in the incidence of gastric cancer. Japan, Chile and Italy have carcinomas from an initial stage of in situ carcinoma
the highest recorded death rate from gastric cancer, while confined to mucosal layers called early gastric carcinoma
the incidence is considerably low in the US, UK and Canada. (EGC) has been found. EGC eventually penetrates the
The higher incidence in certain geographic regions is the muscularis or beyond, resulting in advanced gastric
result of environmental influences as observed from the carcinoma. Accordingly, gastric carcinomas are broadly
finding of incidence of gastric cancer in the next generation classified into 2 main groups:
of Japanese immigrants to the US which is comparable to I. Early gastric carcinoma (EGC).
that of native Americans. II. Advanced gastric carcinoma, which has 5 further major
4. Racial factors. Within the country, different ethnic groups gross subtypes:
may have variations in incidence of gastric cancer e.g. i) Ulcerative carcinoma
incidence is higher in Blacks, American Indians, Chinese in ii) Fungating (Polypoid) carcinoma
Indonesia, North Wales than other parts of Wales. iii) Scirrhous carcinoma (Linitis plastica)
iv) Colloid (Mucoid) carcinoma
5. Genetic factors. Genetic influences have some role in the v) Ulcer-cancer
etiology of gastric cancer. Not more than 4% of patients of In addition to the above classification, gastric
gastric cancer have a family history of this disease.
Individuals with blood group A have higher tendency to carcinomas have been classified, on the basis of extent of
invasion, into 2 groups:
develop gastric cancer (Recall that the peptic ulcer is more