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stomach II

الكلية كلية طب الاسنان     القسم  العلوم الاساسية     المرحلة 3
أستاذ المادة علي زكي ناجي الاسدي       25/06/2019 10:04:34
General pathology

Tumors of the stomach: lect – 11 – Dr. Ali Zeki
1- Benign tumors:
In the GIT, the polyp is applied to any nodule or mass that projects above the level of the surrounding mucosa. Gastric polyps are uncommon, found in about 0.4% of adult autopsies and 3 to 5% of Japanese adults. Although gastric polyps are usually found incidentally, dyspepsia or anemia resulting from blood loss may associated with gastric polyps.
MORPHOLOGY.
They divided into the following types:
1- hyperplastic polyps:
they represents (>90%) of gastric polyps, these polyps are composed of a variable admixture of hyperplastic surface epithelium and cystic dilated glandular tissue, with a lamina propria containing increased inflammatory cells. Most hyperplastic polyps are small and sessile; some may approach several centimeters in diameter and have an apparent stalk. Hyperplastic polyps are seen most frequently in the setting of chronic gastritis. They are regarded as having no malignant potential
2- The adenoma of the stomach is a true neoplasm, representing 5 to 10% of the polypoid lesions in the stomach. By definition, an adenoma contains proliferative dysplastic epithelium and thereby has malignant potential. Adenomatous polyps are much more common in the colon .Gastric adenomas may be sessile (without a stalk) or pedunculated (stalked). The most common location is the antrum. These lesions are usually single and may grow up to 3 to 4 cm in size before detection . the incidence of gastric adenomas increases with age, particularly into and beyond the sixties. The male-to-female ratio is 2:1. Up to 40% of gastric adenomas contain a focus of carcinoma at the time of diagnosis.

2-Malignant tumors:
• carcinoma (90 to 95%), they develop from epithelial mucosal glands.
• lymphomas (4%), they develop from the lymphoid tissue.
• carcinoids (3%), they develop from neuro-endocrine cells.
• malignant stromal cell tumors (2%), they develop from mesenchymal cells of the stomach wall.
GASTRIC CARCINOMA
Among the malignant tumors that occur in the stomach, carcinoma is the most important and the most common (90 to 95%).
Epidemiology.
Gastric carcinoma is a worldwide disease. Its incidence, however, varies widely, being particularly high in countries such as Japan, Chile, China, and Russia. It is more common in lower socioeconomic groups and exhibits a male-to-female ratio of about 2:1.
It remains among the leading killer cancers. Although 5-year survival rates have improved since the advent of endoscopy in the 1960, they remain poor at less than 20% overall.
Gastric carcinoma can be divided into two general histologic subtypes:
(1) (INTESTINAL TYPE):
Those exhibiting an intestinal morphology with the formation of bulky tumors composed of glandular structures, The intestinal type exhibits a mean age of incidence of 55 years and a male-to-female ratio of 2:1, The intestinal variant is composed of neoplastic intestinal glands resembling those of colonic Adenocarcinoma. The neoplastic cells often contain apical mucin vacuoles, and abundant mucin may be present in gland lumens.
(2) (DIFFUSE TYPE, Signet Ring type):
Those that are diffuse in the infiltrative growth of poorly differentiated discohesive malignant cells.. The diffuse type occurs in slightly younger patients (mean age, 48), with an approximately equal male-to-female ratio. The diffuse variant is composed of gastric-type mucous cells, which generally do not form glands but rather permeate the mucosa and wall as scattered individual cells or small clusters in an infiltrative growth pattern. These cells appear to arise from the middle layer of the mucosa, and the presence of intestinal metaplasia is not a prerequisite. In this variant, mucin formation expands the malignant cells and pushes the nucleus to periphery, creating a signet ring conformation .
Causes and risk factors.
1-Environmental
Diet
Nitrites derived from nitrates (water, preserved food)
Smoked and salted foods, pickled vegetables
Lack of fresh fruit and vegetables
Low socioeconomic status
Cigarette smoking
2-Host Factors
Chronic gastritis
Hypochlorhydria: favors colonization with Helicobacter pylori
Intestinal metaplasia is a precursor lesion
Infection by H. pylori that resent in most cases of intestinal-type carcinoma
Partial gastrectomy that favors reflux of bilious, alkaline intestinal fluid
Gastric adenomas
40% harbor cancer at time of diagnosis
30% have adjacent cancer at time of diagnosis
Barrett esophagus
Increased risk of gastroesophageal junction tumors
Genetic
Slightly increased risk with blood group A
Family history of gastric cancer
Hereditary nonpolyposis colon cancer syndrome

MORPHOLOGY.
The location of gastric carcinomas within the stomach is as follows: pylorus and antrum, 50 to 60%; cardia, 25%; and the remainder in the body and fundus.
The three macroscopic growth patterns of gastric carcinoma, which may be evident at both the early and the advanced stages, are (1) exophytic, with protrusion of a tumor mass 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.
Clinical Features.
Gastric carcinoma is an insidious disease that is generally asymptomatic until late in its course. The symptoms include weight loss; abdominal pain; anorexia; vomiting; altered bowel habits; and, less frequently, dysphagia, anemic symptoms, and hemorrhage. Because these symptoms are essentially nonspecific, early detection of gastric cancer is difficult.
The prognosis for gastric carcinoma depends primarily on the depth of invasion and the extent of nodal and distant metastasis at the time of diagnosis; histologic type has minimal independent prognostic significance. The 5-year survival rate of surgically treated early gastric cancer is 90 to 95%, with only a small negative increment if lymph node metastases are present. In contrast, the 5- year survival rate for advanced gastric cancer remains below 15%.


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