Differential Trends in the Intestinal and Diffuse Types of Gastric Carcinoma in the United States, 1973-2000: Increase in the Signet Ring Cell Type

Archives of Pathology & Laboratory Medicine,  Jul 2004  by Henson, Donald Earl,  Dittus, Christopher,  Younes, Mamoun,  Nguyen, Hong,  Albores-Saavedra, Jorge

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Context.-During the last 50 years, the incidence and mortality of gastric cancer has declined in many countries. This decline has primarily included the intestinal type (Lauren classification). However, there is an impression among pathologists that the diffuse type, especially the signet ring cell subtype, has become more prevalent.

Objectives.-Using data from the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute, we analyzed the trends of the 2 primary types (intestinal and diffuse) of gastric carcinomas from 1973 through 2000.

Design.-Trends in age-adjusted rates were determined for gastric carcinomas through the SEER statistical program (SEER*Stat), which is available on the Internet to the public.

Results.-During the period studied, the intestinal type continued to decline in males, females, African Americans, and whites. The intestinal type was more common in males than in females and more common in African Americans than in whites. In contrast, a consistent increase in the rate of the diffuse type of gastric carcinoma was seen during this period. The rate increased from 0.3 cases per 100 000 persons in 1973 to 1.8 cases per 100 000 persons in 2000. This increase was seen in males, females, African Americans, and whites. The predominant increase occurred in the signet ring type.

Conclusions.-The results indicate a progressive decrease in the incidence of the intestinal type of gastric cancer and an increase in the diffuse type of gastric carcinoma, especially the signet ring cell type. The clinical implications of the increase are considered.

(Arch Pathol Lab Med. 2004;128:765-770)

Gastric carcinoma is one of the leading causes of cancer death worldwide. Although recent focus has been on the rising incidence of carcinoma of the gastric cardia and adenocarcinoma of the esophagus,1-3 the incidence and mortality of gastric carcinoma in the United States has been declining for many years.4 However, there is an impression among pathologists that the signet ring cell type of diffuse carcinoma has been increasing. Recent studies have suggested that signet ring cell tumors are distinct at the molecular level5-9 and are less related to cigarette smoking10 or fruit and vegetable consumption11 than the conventional type, indicating different pathogenetic mechanisms.

For this article, we reviewed the trends of the 2 main types of gastric carcinoma, intestinal and diffuse,12 from 1973 through 2000 as recorded in the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute. Histologic trends were also compared in males and females and in African Americans and whites.

MATERIALS AND METHODS

Data were obtained from the SEER Program for the years 1973 through 2000. The SEER Program covers 11 geographic areas: Atlanta, Ga; Connecticut; Detroit, Mich; Hawaii; Iowa; Los Angeles, Calif; New Mexico; San Francisco-Oakland, Calif; San Jose-Monterey, Calif; Seattle-Puget Sound; and Utah. These areas include approximately 12% of the US population and represent national demographic patterns. Population-based from inception, SEER has accrued data through regional and statewide tumor registries.13 It contains a comprehensive recording of histopathologic diagnoses on patients with cancer.

Incidence rates are expressed as per 100 000 persons and are age-adjusted to the 2000 US census as standard for the population. Rates were based on the histologic types of stomach cancer as reported to SEER. In situ carcinomas were excluded. All racial/ethnic groups were omitted except for whites and African Americans.

Histology Codes

The histologic types were recorded from the pathology reports according to the International Classification of Disease for Oncology (ICD-O). Although a number of classifications for gastric carcinoma have been published,14 we focused on the Lauren classification.12 In SEER, there are 3 diagnostic codes for the diffuse type of gastric carcinoma that correspond to the Lauren classification. They include signet ring cell carcinoma (M8490), diffuse carcinoma (M8145), and linitis plastica (M8142). Linitis plastica is a gross descriptive term, which can refer to a signet ring cell and/or diffuse carcinoma within the wall of the stomach. However, it is occasionally used as the primary diagnostic term and is coded as such in ICD-O. Diffuse carcinoma can refer to several types, including small cell or poorly differentiated types that diffusely infiltrate the wall of the stomach. In this article, the term diffuse type refers to the combination of all 3 codes. According to the coding rules used in SEER, it is not possible to assign more than 1 code number to the same tumor. The intestinal type included all cases recorded as "carcinoma, not otherwise specified [NOS]"; "adenocarcinoma, NOS"; "tubular"; and "intestinal type" (M8010, M8140, M8211, and M8144, respectively). These combined codes for the intestinal type included 76% of all gastric carcinomas reported to SEER. Other tumor types, such as carcinoid and small cell carcinoma, were excluded because they are either very rare or else it was uncertain whether they behaved according to the diffuse or intestinal type.