Stomach is a J-shaped hollow organ located on the left side in the abdomen. It also produces acid and enzymes to aid in the digestion of food.Present between the esophagus and small intestine, It is a vital part of the digestive system.The digestive system aids in digestion by breaking down complex food into fine particles so it can be absorbed by the body.

Parts of the Stomach 

Cardia: The cardia is the first part of the stomach and serves as the point of connection between the esophagus and the stomach. It features a specialized sphincter that regulates the flow of food into the stomach.

Fundus: Following the cardia, the fundus is positioned in the upper part of the stomach. Characterized by its round shape, it is responsible for temporarily storing ingested food.

Body: The body constitutes the largest section of the stomach and comes after the fundus. Here, the process of mixing food with gastric juices occurs, facilitating digestion.

Antrum: After the body of the stomach, the antrum takes over. This area is designated for the temporary storage of food until it's prepared for further movement.

Pylorus: Serving as the connection point between the stomach and the small intestine, known as the duodenum, the pylorus acts as a valve. It controls the regulated passage of food from the stomach to the small intestine, playing a crucial role in digestion and the transfer of nutrients.

The stomach wall 

1. Mucosa : The innermost stomach layer producing protective mucus against stomach acid and enzymes.
2. Submucosa: Houses blood vessels, nerves, and lymph vessels to support stomach functions.
3. Muscle Layer: Smooth muscles that mechanically churn and propel food through the stomach.
4. Subserosa: Connective tissue layer providing structural support within the stomach wall.
5. Serosa: Outermost layer offering protection and smooth surface, anchoring the stomach in the abdominal cavity.

Function of the Stomach

Upon food entry, the stomach releases gastric juices and undergoes contractions that aid in digestion. These contractions convert the food bolus into semi-fluid form called chyme, which then passes into the small intestine through the pylorus.

Stomach Cancer

Most stomach cancers are adenocarcinomas, arising from mucus-producing cells. They typically begin in the inner mucosa and can spread to deeper layers, invading submucosa and serosa. Metastasis occurs through nearby blood vessels, veins, and lymph nodes. Precancerous changes in the mucosa may remain asymptomatic initially.

Stages of Spread

1. Early Stage: Cancer is confined to the mucosa without invading deeper layers or lymph nodes.
2. Locally Advanced: Cancer penetrates the stomach wall, affects nearby lymph nodes, and impacts adjacent organs.
3. Metastasized: Cancer spreads to distant regions such as the liver, peritoneum (abdominal lining), lungs, and bones.

Diagnosis of stomach cancer

• Medical History: A comprehensive medical history is vital for effective treatment planning. Disclose past infections, injuries (like H. pylori), and medication details to inform decisions.
• Complete Blood Count (CBC): This test assesses Red Blood Cells (RBCs), White Blood Cells (WBCs), and platelets, aiding in conditions like Anemia detection.
• CA-19 and CEA: Cancer Antigen 19-9 (CA-19-9) and Carcinoembryonic Antigen (CEA) are antigens in blood used to detect tumors. These tests provide valuable insights for cancer diagnosis and monitoring.
• CT Scan (Computed Tomography): CT scans utilize X-rays to create detailed cross-sectional images of internal body parts. These images aid in cancer treatment planning. Contrast material can be administered to enhance image quality.
• PET Scan (Positron Emission Tomography): PET scans involve a radioactive sugar molecule that highlights cancerous cells as they metabolize the sugar. The resulting bright areas on the scan provide insight into cancer activity. PET can be combined with CT for better accuracy.
• FDG PET/CT (F-18 Fluorodeoxyglucose PET/CT): Similar to PET scans, FDG PET/CT uses a radioactive sugar (FDG) to visualize cancerous cells, particularly useful for detecting cancer spread and lymph nodes involvement.
• Ultrasound: Ultrasound employs sound waves to generate images of internal body parts without using X-rays. It is safe and commonly used for visualizing organs.
• Endoscopy: Endoscopy involves inserting a thin, flexible tube through natural orifices (mouth, anus, nose) or through an incision to view organs. The tube has a camera for detailed visual inspection.
• Endoscopic Ultrasound: Combining endoscopy and ultrasound, this technique provides precise images of how much cancer has spread, especially for assessing metastasis.
• Laparoscopy: Laparoscopy is an endoscopic procedure to view the abdomen. A laparoscope is inserted through an abdominal incision. 
• H. pylori Test: This test detects H. pylori infection, a risk factor for stomach cancer. Treating this infection can reduce cancer risk.
• Biopsy: Biopsies involve removing tissue samples, often guided by endoscopy. Fine needle aspiration (FNA) is one method, and biomarker testing can be performed on biopsy samples.
• Biomarker Testing: Biomarkers in biopsy samples, like HER2 and PDL-1, offer insights into cancer behavior and help with treatment planning.
• HER2 (Human Epidermal Growth Factor 2): Elevated HER2 levels can lead to excessive cell growth. HER2-positive stomach cancer can be targeted with specific therapies.
• PDL-1 Testing: PDL-1 expression by cancer cells indicates potential efficacy of chemotherapy and immune checkpoint inhibitor therapies. Absence suggests resistance to immune cell attack.

These diagnostic methods provide crucial information for accurately diagnosing stomach cancer, determining its stage, and tailoring appropriate treatment strategies for patients.