• The most common benign tumor in the stomach is the polyp. (hyperplastic polyp - most often, fundic gland polyp, adenomatous polyp).
Fundic gland polyp is particularly associated with long-term use of PPIs.
• The majority of stomach cancers are adenocancers (85%) and lymphomas (12%).
• The stomach is the most common site of extranodal lymphoma and gastrointestinal stromal tumor (GIST).
Adenocancer
Etiology and Risk Factors
• Nutritional factors (most important)
High nitrate/nitrite content found in smoked, salted or dried foods
Diet poor in nitrosamines, vegetables and fruits
Vitamin A and C deficiency
• H. Pylori infection
• Low socioeconomic status
• Adenomatous polyp and hereditary polyposis/non-polyposis syndromes
• Intestinal metaplasia (incomplete type)
• Cigarette
• Alcohol (for heavy drinkers)
• Plastic and coal mine worker
• Akan group (genetic disposition)
• Genetics: E-cadherin (CDH1), p53 , APC
• Pernicious anemia, atrophic gastritis, achlorhydria
• Postgastrectomy
Classification
• Stomach cancers are evaluated as early and advanced:
Early gastric cancer are tumors confined to the mucosa and submucosa, with or without lymph node involvement.
• Gastric cancers are examined as intestinal type and diffuse type according to Lauren classification:
Clinic
• The most common symptom is abdominal pain, weight loss and loss of appetite are common in advanced cases.
• Dysphagia in cardia tumors, nausea and vomiting may occur as a result of narrowing of the pyloric canal or lumen in antrum tumors.
• Paraneoplastic syndromes such as acanthosis nigricans, seborrheic keratosis (Leser Trelat sign) may develop.
• DiK and migratory thrombophlebitis (Trousseau's syndrome) may be seen, especially in mucinous adenocarcinomas.
Metastasis pattern of gastric cancers
• It most commonly metastasizes to the liver by hematogenous route.
• It can spread to the left supraclavicular lymph node via the lymphatic system (Wirchow node)
• Peritoneal carcinomatosis and malignant ascites may develop as a result of peritoneal involvement.
• Metastases to the periumbilical region (Sister Mary Joseph node), ovary (Krukenberg's tumor) and rectal wall (Blummer Shelf) may occur.
Diagnosis and Staging
• First of all, endoscopy should be performed in every patient with suspected gastric cancer. Definitive diagnosis is made by endoscopy + biopsy.
• CEA, CA-19-9, and CA 72-4 may be elevated, but their diagnostic value is limited. They are mostly used to monitor response to treatment.
• Endoscopic USG is used for staging and detecting local spread. CT is used to identify distant metastases.
Treatment
• Endoscopic resection can be performed for tumors confined to the mucosa-submucosa.
• Surgical resection is performed in limited cases to the stomach and regional lymph nodes.
• If there is distant metastasis, palliative treatments are applied.
Gastric Lymphoma
• The most common origin of extranodal lymphomas is the stomach.
• MALT (mucosa associated lymphoid tissue) lymphoma or MAL Toma constitute the majority of gastric lymphomas. In addition, the stomach is an area where nodal lymphomas spread frequently.
• MALToma is a low-grade, B-cell non-Hogdkin lymphoma.
• Diagnosis is made by endoscopy+biopsy. In the biopsy, there is CD20+ lymphoepithelial cell infiltration.
Treatment
In early cases, the tumor may regress with eradication of H. Pylori. Cases with t(11;18) do not respond to H. Pylori eradication.
" In advanced cases, surgery can be applied if the tumor is localized, and chemotherapy can be applied if it has spread.
Gastrointestinal Stromal Tumor
They are the most common mesenchymal tumors of the gastrointestinal tract.
• They most often settle in the stomach.
• It is characterized by the C-kit gene mutation (CD-117).
• This tumor originates from Cajal cells.
• EUS is very valuable in diagnosis (demonstration of submucosal lesions).
• Prognostic factors; number of mitoses, tumor size, tumor location (good prognosis in stomach, poor prognosis in small intestine)
• Surgery is the treatment in limited cases, imatinib (alternative sunitinib), a tyrosine kinase inhibitor, can be used in metastatic cases. Cases with an Exon 11 mutation respond better to imatinib.
