An animal model of stomach carcinogenesis was established using Mongolian gerbils with Nmethyl-N-nitrosourea (MNU) and N-methyl-N′ ′ ′ ′-nitro-N-nitrosoguanidine (MNNG) as the carcinogens. In addition, the sensitivity of these gerbils to Helicobacter pylori (H. pylori) was confirmed. One hundred and sixty specific pathogen-free male MGS/Sea animals, 7 weeks old, were treated with MNU in the drinking water (30 ppm for alternate weeks to give 10 weeks exposure, or 10 ppm or 3 ppm for 20 weeks continuous exposure), or given MNNG in the drinking water at 400 ppm or 200 ppm for 20 weeks, or orally inoculated with ATCC43504 H. pylori (1.7× × × ×10 8 CFUs/animal). Adenocarcinomas in the glandular stomach were found in 2 out of 12 effective animals (2/ 12) treated with 30 ppm MNU at week 20, although all were dead or moribund by week 30 due to MNU toxicity. At week 50, the incidences of gastric adenocarcinomas in groups treated with 10 ppm MNU, 3 ppm MNU, 400 ppm MNNG, and 200 ppm MNNG were 2/21 (9.5%), 1/23 (4.3%), 7/ 11 (63.6%), and 1/10 (10.0%). The lesions were generally well differentiated, although poorly differentiated adenocarcinoma was also found in a single gerbil in each of the 10 ppm MNU and 400 ppm MNNG groups. In control animals no tumors were found. In the infection study, the animals were killed at week 20, and H. pylori was detected in all cases, causing multiple erosions with marked inflammatory cell infiltration in the lamina propria and submucosa, and frequent formation of lymphoid follicles. Thus, MNU and MNNG in the drinking water induced neoplastic lesions in the glandular stomach epithelium of H. pylori-sensitive gerbils.

From January 1976 to December 1987, 37 early colorectal cancers of the flat type were treated. Thirty-four of them (91.9%) were not accompanied by adenoma, and were thought to have arisen de novo. There is indeed a de novo route of cancer development in the human large intestine, and cancers de novo merely show polypoid growth. Flat type cancers arising de novo tend to reach deeper layers at an earlier stage than polypoid-type carcinomas in adenoma. Of those with a diameter of less than 10 mm, only 40% stayed in the mucosa. Consequently, advanced cancers cannot be prevented by snare polypectomy alone. More attention should be directed to the discovery of small, flat, nonpolypoid cancers.

Background : Various types of classification of gastritis have been proposed, but no plausible classification has been available until now. The Research Society for Gastritis performed a pilot study to establish an endoscopic classification, taking into consideration the following: (i) ease of use; (ii) permitting everyone the common image; and (iii) presence of histopathological evidence. Methods : One hundred and fifty-five patients were enrolled and underwent gastroscopy. Eight basic endoscopic and histological types of gastritis (superficial, hemorrhagic, erosive, verrucous, atrophic, metaplastic, hyperplastic and special types) were defined. Gastritis was endoscopically diagnosed according to the definition of the endoscopic types of gastritis. Four or more biopsy specimens were obtained from the lesser and the greater curvatures of the antrum and the corpus of each patient, and the histological findings of gastritis and Helicobacter pylori infection were assessed. The histological diagnosis of gastritis was made according to the definition of histology types of gastritis. The endoscopic and the histological diagnoses were then compared in a blinded fashion. Results : Endoscopic diagnosis was 62% as sensitive as histological diagnosis for erosive gastritis, 67% for verrucous gastritis and 84% for atrophic gastritis in the antrum. In superficial gastritis, sensitivity was approximately 25% in the corpus, but only 8% in the antrum. Metaplastic and hyperplastic gastritis were correctly diagnosed only in severe cases. Conclusion : Five basic types of gastritis (superficial, erosive, verrucous, atrophic and special types) should be employed for the new endoscopic gastritis classification. Metaplastic and hyperplastic gastritis are considered to be subtypes of atrophic gastritis and they should be excluded from the basic endoscopic classification. A new definition of gastritis in the antrum accompanied by redness still remains to be investigated.

In order to search for the histogenesis and progression of colorectal cancer, the background mucosas of 18 patients with a single colorectal cancer, apart from familial adenomatosis coli, were studied by a step sectioning method. Three early minute cancers (3-5 mm in diameter) were detected in the apparently normal mucosa, and two cancers in the adenoma (focal cancer in adenomatous polyp). The three early cancers had no evidence of preexisting adenoma, so they were considered to be de novo cancers. In form they were depressed, flat, and slightly elevated. In humans, de novo cancer has an important significance in histogenesis and treatment of colorectal cancer. Clinically, it is also important to recognize the early phase of colorectal cancer in flat type as well as polypoid type.

No abstract