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Fig. 3.06 Endoscopic views of gastric cancer (A, C) and corresponding images with dye enhancement (B, D). Fig. 3.08 Gastric adenocarcinoma of (A) polypoid A, B Depressed early gastric cancer. C, D Deep ulcer scar surrounded by superficial early gastric cancer infil- and (B) diffusely infiltrative type. trating the mucosa and submucosa.

Fig. 3.06 Endoscopic views of gastric cancer (A, C) and corresponding images with dye enhancement (B, D). Fig. 3.08 Gastric adenocarcinoma of (A) polypoid A, B Depressed early gastric cancer. C, D Deep ulcer scar surrounded by superficial early gastric cancer infil- and (B) diffusely infiltrative type. trating the mucosa and submucosa.

trie cancers, radiology usually is not necessary, but may complement endoscopic findings in some cases. Tumour staging prior to treatment decision involves percutaneous ultrasound or computerized tomography to detect liver metastases and distant lymph node metastases. Laparoscopic staging may be the only way to exclude peritoneal seeding in the absence of ascites.

Polypoid Fungating

Polypoid Fungating

Ulcerated Infiltrative

Fig. 3.07 Borrmann classification of advanced gastric carcinoma.

Ulcerated Infiltrative

Fig. 3.07 Borrmann classification of advanced gastric carcinoma.

Macroscopy

Dysplasia may present as a flat lesion (difficult to detect on conventional endo-scopy, but apparent on dye-staining endoscopy) or polypoid growth. Appearances intermediate between them include a depressed or reddish or discolored mucosa. The macroscopic type of early gastric carcinoma is classified using critera similar to those in endoscopy (Fig. 3.03) {1298, 63}. The gross appearance of advanced carcinoma forms the basis of the Borrmann classification (Fig. 3.06) {63, 175}.

Ulcerating types II or III are common. Diffuse (infiltrative) tumours (type IV) spread superficially in the mucosa and submucosa, producing flat, plaque-like lesions, with or without shallow ulcerations. With extensive infiltration, a linitis plastica or 'leather bottle' stomach results. Mucinous adenocarcinomas appear gelatinous with a glistening cut surface.

Tumour spread and staging

Gastric carcinomas spread by direct extension, metastasis or peritoneal dissemination. Direct tumour extension involves adjacent organs. Tumours invading the duodenum are most often of the diffuse type and the frequency of seros-al, lymphatic, and vascular invasion and lymph node metastases in these lesions is high. Duodenal invasion may occur through the submucosa or subserosa or via the submucosal lymphatics. Duodenal invasion occurs more frequently than expected based on gross examination. Therefore, resection margins should be monitored by intraoperative consultation.

Intestinal carcinomas preferentially meta-stasize haematogenously to the liver, whereas diffuse carcinomas preferentially metastasize to peritoneal surfaces {1273, 245}. An equal incidence of lymph node metastases occurs in both types of tumours with T2 or higher lesions. Mixed tumours exhibit the metastatic patterns of both intestinal and diffuse types. When carcinoma penetrates the serosa, peritoneal implants flourish. Bilateral massive ovarian involvement (Krukenberg tumour) can result from transperitoneal or haema-togenous spread.

The principal value of nodal dissection is the detection and removal of metastatic disease and appropriate tumour staging. The accuracy of pathological staging is proportional to the number of regional lymph nodes examined and their location. When only nodes close to the tumour are assessed, many cancers are classified incorrectly.

Histopathology

Gastric adenocarcinomas are either gland-forming malignancies composed

Fig. 3.09 A Depressed adenocarcinoma. B Depressed signet ring cell carcinoma. C Gastric cancer, dye sprayed (pale area). D, E, F Advanced gastric carcinoma with varying degrees of infiltration.

Fig. 3.09 A Depressed adenocarcinoma. B Depressed signet ring cell carcinoma. C Gastric cancer, dye sprayed (pale area). D, E, F Advanced gastric carcinoma with varying degrees of infiltration.

of tubular, acinar or papillary structures, or they consist of a complex mixture of discohesive, isolated cells with variable morphologies, sometimes in combination with glandular, trabecular or alveolar solid structures {243}. Several classification systems have been proposed, including Ming, Carniero, and Goseki {1623}, but the most commonly used are those of WHO and Lauren {419, 87}.

WHO classification

Despite their histological variability, usually one of four patterns predominates. The diagnosis is based on the predominant histological pattern.

Tubular adenocarcinomas

These contain prominent dilated or slitlike and branching tubules varying in their diameter; acinar structures may be

. IT \fc 'i present. Individual tumour cells are columnar, cuboidal, or flattened by intraluminal mucin. Clear cells may also be present. The degree of cytological atypia varies from low to high-grade {466, 1362}. A poorly differentiated variant is sometimes called solid carcinoma. Tumours with a prominent lymphoid stro-ma are sometimes called medullary carcinomas or carcinomas with lymphoid stroma {2063}. The degree of desmopla-sia varies and may be conspicuous.

Papillary adenocarcinomas

These are well-differentiated exophytic carcinomas with elongated finger-like processes lined by cylindrical or cuboidal cells supported by fibrovascu-lar connective tissue cores. The cells tend to maintain their polarity. Some tumours show tubular differentiation

(papillotubular). Rarely, a micropapillary architecture is present. The degree of cellular atypia and mitotic index vary; there may be severe nuclear atypia. The invading tumour edge is usually sharply demarcated from surrounding structures; the tumour may be infiltrated by acute and chronic inflammatory cells.

Mucinous adenocarcinomas

By definition, > 50% of the tumour contains extracellular mucinous pools. The two major growth patterns are (1) glands lined by a columnar mucous-secreting epithelium together with interstitial mucin and (2) chains or irregular cell clusters floating freely in mucinous lakes. There may also be mucin in the interglandular stroma. Scattered signet-ring cells, when present, do not dominate the histological picture. Grading mucinous adenocarci-

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