09 tumors of stomach 2016

TUMORS OF STOMACH • Tumors arising from the mucosa predominate over mesenchymal tumors.

• Mucosal tumors are classified into: – polyps and – carcinoma

Gastric Polyps • Polyp: a nodule or mass that projects above the level of the surrounding mucosa, lined by indigenous epithelium.

– Occasionally, a lipoma or leiomyoma may protrude to produce polypoid lesion.

• Gastric polyps are uncommon as compared with colonic polyps • Types of polyps in stomach: • (1) hyperplastic, (2) fundic gland & (3) adenomatous polyps • All three arise in the setting of chronic gastritis – Hyperplastic and fundic gland polyps are essentially innocuous.

– Adenomatous polyp may harbor adenocarcinoma

Morphology • Hyperplastic polyps due to reparative chronic mucosal damage; – composed of a hyperplastic mucosal epithelium and an inflamed edematous stroma.

– not true neoplasms.

• Fundic gland polyps: are small hamartomas • Adenomas contain dysplastic epithelium.

– true neoplasms

Gastric Carcinoma • Among the malignant tumors of stomach, – carcinoma is most important and the most common (90% to 95%).

• Next are: – lymphomas (4%), – carcinoids (3%), and – stromal tumors (2%).

Epidemiology and Classification • Gastric carcinoma is the second leading cause of cancer-related deaths in the world • Japan and South Korea have the highest incidence • China, Chile and Costa Rica; also high.

Risk factors for Gastric Carcinoma • Intestinal type: – In intestinal metaplasia due to chronic gastritis.

– Better differentiated and more in high-risk populations.

– after age 50 years with a 2 : 1 male predominance

• Diffuse variant: – thought to arise de novo – not associated with chronic gastritis, – poorly differentiated and occurs at an earlier age with female predominance

Risk factors • Intestinal-Type Adenocarcinoma – Chronic gastritis with intestinal metaplasia – Helicobacter pylori Infection – Nitrites derived from nitrates (drinking water, preservatives in prepared meats) – Diets generating nitrites (smoked foods, pickled vegetables and excessive salt intake) – Decreased intake of fresh vegetables and fruits – Pernicious anemia

• Diffuse Carcinoma • Risk factors undefined, except for a rare inherited mutation of Ecadherin

Intestinal-Type Adenocarcinoma • Predisposing influences are many, but their relative importance is changing e.g.: – increased use of refrigeration decreasing the need for food preservation by nitrates, smoking, and salt – chronic gastritis associated with H. pylori infection- major risk factor for gastric carcinoma – H. pylori may release reactive oxygen species-cause DNA damage

• Amplification of HER-2/NEU and increased expression of β-catenin are present in 20% to 30% of cases

Diffuse Adenocarcinoma • Risk factors: undefined and no precursor lesions • Mutations in E-cadherin in 50% ( but not detectable in intestinal-type) • Some patients may have a hereditary diffuse gastric cancer, caused by germ-line mutation in E-cadherin.

• Mutations in FGFR2, a member of the fibroblast growth factor receptor family, and • increased expression of metalloproteinases are present in about one-third of cases

Morphology • Location: – pylorus and antrum, 50% to 60%; – cardia, 25%; and – remainder in the body and fundus.

– lesser curvature is involved in about 40% and the greater curvature in 12%.

• Thus, a favored location is the lesser curvature of the antropyloric region.

Morphologic types • Classified on the basis of: – depth of invasion, – macroscopic growth pattern, and – histologic subtype.

Morphologic types • Morphologic feature having the greatest impact on clinical outcome is the depth of invasion.

• Early gastric carcinoma: – lesion confined to mucosa and submucosa, regardless of presence or absence of perigastric lymph node metastases.

• Advanced gastric carcinoma: – neoplasm that has extended below the submucosa into the muscular wall and has perhaps spread more widely.

Growth pattern • (1) exophytic: protrusion into the lumen; • (2) flat or depressed, in which there is no obvious tumor mass within the mucosa; and • (3) excavated, whereby a shallow or deeply erosive crater is present in the wall of the stomach (may mimic chronic peptic ulcers) • If broad region of the gastric wall is extensively infiltrated by malignancy

– thickened stomach; c/a leather bottle stomach, or linitis plastica;

Morphology: Microscopic • Intestinal variant: – composed of malignant cells forming neoplastic intestinal glands resembling colonic adenocarcinoma.

• Diffuse variant: – composed of gastric-type mucous cells – generally do not form glands – permeate the mucosa and wall as scattered "signet-ring" cells – or small clusters in an "infiltrative" growth pattern.

Advance stage of Gastric Carcinoma • Whatever the histologic variant

– eventually penetrate the wall to involve the serosa, – spread to regional and more distant lymph nodes, – and metastasize widely.

• Earliest lymph node metastasis: supraclavicular lymph node (Virchow node).

• Intraperitoneal spread in females is to both the ovaries: Krukenberg tumor

Ulcerative gastric carcinoma Ulcer is large with irregular, heaped-up margins.

Extensive excavation of the gastric mucosa with a necrotic gray area in the deepest portion

Gastric cancer.

A, Intestinal type with gland formation by malignant cells that are invading the muscular wall B, Diffuse type with signet-ring cells.

Clinical Features • Both types of carcinoma are generally:

– asymptomatic; discovered by repeated endoscopic examinations

• Advanced carcinoma often first comes to light because of abdominal discomfort or weight loss.

• Uncommonly dysphagia if located in the cardia or obstructive symptoms when they arise in the pyloric canal.