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Involvement of regional lymph nodes (N) is estimated according to the scheme which follows below. Regional lymph nodes include pericardial, left ventricular, common liver, splenic, and those of the celiac artery. Involvement of the other intra-abdom-inal lymph nodes (hepatoduodenal, retropancreat-ic, mesenteric, and para-aortic) are regarded as distal metastases.

™ Nx - regional lymph nodes cannot be evaluated ™ No - no metastases to the regional lymph nodes ™ Ni - metastases to the regional lymph nodes within a distance of 3 cm from the margin of the primary tumor ™ N2 - metastases to the regional lymph nodes located farther than 3 cm from the margin of the primary tumor, or metastases to the lymph nodes along the entire left border of the stomach, common hepatic, splenic, and iliac artery ™ Remote metastases:

- Mx - presence of remote metastases cannot be estimated

- Mo - no remote metastases

- Mi - remote metastases

The proposed scheme is recommended only for carcinomas and should not be used to evaluate sarcomas, carcinoids, or lymphomas.

Gastric cancer is characterized by high variability, multiple forms, and combinations of various macroscopic forms. A great number of factors influence tumor growth: its histological structure, location, stage of the process, degree of hyperplastic (background) changes in the stomach wall, involvement of the stromal component, immune response of the body, age of the patient. However, it is possible to identify the major variants. The macroscopic concepts of gastric cancer are based on the first classification proposed by R. Borrmann in 1926 [96]. However, classifications which were proposed later proved more popular. They were produced by P. Laurent [78, 179], S. Ming [197], the WHO (1990) [272], and the American Joint Committee on Cancer (1992) [248]. The classification proposed by the Japanese Gastric Cancer Association [153] is now widely used. It identifies the following macroscopic types of gastric cancer:

™ Type o - superficially spreading carcinoma, subdivided into five subtypes, presented in the section dedicated to early cancer ™ Type 1 - polypiform

™ Type 2 - ulcerating cancer with distinct borders and elevated edges ™ Type 3 - ulcerating cancer infiltrating the surrounding tissues ™ Type 4 - unclassifiable tumor; as a rule, this is diffusely propagating cancer without ulceration

Superficially Spreading Gastric Cancer

Superficially spreading gastric cancer (D Fig. 6) is the earliest macroscopically visible form of gastric cancer [249]. The tumor growing in the surface of the mucous and submucous membrane is characterized by an elevated or sinking surface, sometimes affected with small ulcers; the area of carcinoma does not exceed 25 mm2. The tumor tends to stretch mucosal folds, making them rigid, and to fix them to the muscular coat. In about 80% of cases the stomach wall is thickened to 0.8-1.0 m (versus normal 0.60.7 m in the pyloric part and 0.4-0.7 m in the body) due to sclerosis and edema of the submucous membrane of varying degrees. The depth of invasion corresponds mostly to Tins-T1, less frequently T2. All forms of gastric cancer which will be described below develop later. Histologically, superficially spreading gastric cancer has, in most cases, the structure of poorly differentiated adenocarcinoma or signetring cell carcinoma.

D Fig. 6. a Fragment of a macrospecimen of a resected stomach. A 6x4-cm specimen of the mucous membrane with an elevated surface in the region of the greater curvature affected with 0.2- to 0.6-cm ulcers.
□ Fig. 6. b Fragment of a microspecimen of gastric mucosa with growing complexes of poorly differentiated adenocarcinoma on the proper mucous membrane surface. Hematoxylin and eosin, x100

Polypiform Cancer of the Stomach

Polypiform cancer of the stomach (□ Fig. 7) occurs in 17% of cases. The tumor grows into the stomach cavity and varies in shape and size. As a rule, this is the late stage of endophytic carcinoma. Histologi-cally, it has the structure of tubular or papillary well-differentiated adenocarcinoma, possibly with formation of mucus, and sometimes developing against the background of preceding adenoma.

Ulcerated Cancer of the Stomach

Ulcerated cancer of the stomach (Figs. 1, 2, 4) occurs in 25% of cases. This is an endophytic tumor of variable size, with rigid elevated or eroded edges, surrounded by a ridge of infiltrated tissue and converging flattened folds of the mucous membrane. The floor of the ulcer formed by cell detritus is rough. In section, the wall is usually 0.8-1.5 cm thick. These changes are due to sclerosis of the submucous membrane and specific cancer infiltration spreading between muscular strands and attended by desmoplas-tic response of varying degree. Firm, whitish cancer

□ Fig. 7. a Fragment of a macrospecimen of a resected stomach. A 1.5x1.5x0.7-cm polypiform tumor (arrow) is seen in the immediate vicinity of the gastroesophageal junction. Histologically, an adenocarcinoma invading the submucous membrane. b The same preparation (section). Exophytic growth appears as a whitish firm tissue (arrows)

□ Fig. 7. a Fragment of a macrospecimen of a resected stomach. A 1.5x1.5x0.7-cm polypiform tumor (arrow) is seen in the immediate vicinity of the gastroesophageal junction. Histologically, an adenocarcinoma invading the submucous membrane. b The same preparation (section). Exophytic growth appears as a whitish firm tissue (arrows)

tissue underlies the ulcer over a length of 2-3 cm on each side. This tissue normally grows into the serous membrane (□ Fig. 8); the depth of invasion corresponds to T1-T3. Ulcerated carcinomas have the structure of both intestinal and diffuse cancer.

Diffusely Spreading Cancer of the Stomach

Diffusely spreading cancer of the stomach (linitis plastica) (□ Fig. 9) occurs in 16% of cases. Massive cancer infiltration combines with a pronounced des-moplasia. Invasion depth corresponds to T2-T3.

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