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[Frequency of gastric lymphoma at 6 hospitals in Mexico City].

BACKGROUND
Gastric lymphoma has been traditionally considered a rare neoplasm that constitutes 1-5% of malignant gastric tumors. Two studies performed in Mexico in 1960 and 1966 found that only 1.9% and 1% of gastric neoplasms were lymphomas. Nevertheless, some studies made in the U.S. and in some European countries in recept decades have revealed an increase in the frequency of this neoplasm. A recent study made at two National Health Institutes in Mexico City (Instituto Nacional de Cancerología and Instituto Nacional de la Nutrición) revealed a remarkable increase in the frequency of gastric lymphoma (9.3% and 10.3%, respectively) in recent years.


AIM
To define whether there is an actual increase of lymphoma in our population and whether it includes other hospitals in Mexico City that provides attention to populations different from those who attend referral centers.


MATERIALS AND METHODS
Six hospitals in Mexico City were selected, including two National Health Institutes (Instituto Nacional de la Nutrición and Instituto Nacional de Cancerología), two private general hospitals used by patient with a high socioeconomic level (Hospital Español and Hospital Inglés), and two public general hospitals frequented by low-income patients (hospital Juárez and Hospital General de México). In each case, the gastric lymphomas diagnosed in each participant hospitals in the last 5 years were registered. For comparative purpose, diagnosed cases of gastric adenocarcinoma during the same period were also registered. Other types of gastric neoplasms were excluded from the study because they formed a very heterogeneous group and represented a minimal proportion of malignant gastric tumors. Age and sex of each patient were included for all lymphomas.


RESULTS
A total of 879 malignant gastric neoplasms were included in our study. The relative percentage for gastric lymphoma by institution in descendent order was Hospital Español 25.4%; Instituto Nacional de la Nutrición 13.7%, Hospital Inglés 11.5%, Hospital General de México 8.5%, Instituto Nacional de Cancerología 6%, and Hospital Juárez 6%. Mean general frequency taking into account the six hospitals was 9.1%.


CONCLUSIONS
Frequency of gastric lymphomas in all analyzed institutions was higher than that reported in most series in the medical literature (1-5%) and that reported for the Mexican population in 1960 and 1966. The increase was most remarkable in hospitals attended by patients with high incomes (Hospital Español, Hospital Inglés), although the total number of neoplasms reported by these institutions was smaller than that reported by hospitals were by patients with lower incomes (Hospital Juárez, Instituto Nacional de Cancerología). The reason for this increase is unknown, but one might speculate that some strains of Helicobacter pylori, nutritional factors, and ethnic differences could be involved. Both gastroenterologists and pathologists must recognize the increase of this neoplasm because unlike gastric adenocarcinoma, gastric lymphoma is a curable disease in a high percentage of cases.