Introduction

Large differences in incidence exist worldwide. Although stomach cancer rates have been steadily decreasing in most populations over the last 4–5 decades, none the less, it still remains the most frequent cancer in the world (Parkin et al., 1988). Many hypotheses have been proposed to explain this general decline, but the causes remain essentially unknown.

Histology, classification and diagnosis

Two main histological types of stomach cancer, which differ not only in morphology but also in their epidemiological characteristics, have been described (Lauren, 1965). The intestinal or expanding adenocarcinoma is characterized by the tendency to form glandular structures resembling the colonic mucosa and has often, grossly, apolypoid appearance. It is more prevalent in males and older age groups. The diffuse or infiltrative type of adenocarcinoma is characterized by lack of cellular cohesiveness and diffuse infiltration of the gastric wall. It is equally frequent in males and females. It is relatively more frequent in younger age-groups, and has a worse prognosis than the intestinal type.

In populations with high or intermediate rates, the intestinal type of cancer predominates, but the diffuse type is more common in populations with low rates (Muñoz, 1988).

The following precursor lesions have been postulated for the intestinal type but none is recognized for the diffuse type.