Gastric cancer is when malignant or cancerous cells arise in the stomach.
This cancer can appear in any part of the stomach and it’s classified into adenocarcinoma, lymphoma, carcinoid tumor, and leiomyosarcoma; depending on the type of cells it originates from.
Adeno- means gland; so, adenocarcinoma arises from columnar glandular epithelium.
Lymphoma arises from lymphocytes.
Carcinoid tumor is originated in the G-cells of the stomach.
And leiomyosarcoma arises from smooth muscle cells from the gastric wall.
Gastric cancer is generally considered a poor prognosis cancer, because it doesn't cause specific symptoms until later stages.
The stomach has four regions: the cardia, the fundus, the body, and the pyloric antrum.
There’s also a pyloric sphincter or valve at the end of the stomach, which closes while eating, keeping food inside for the stomach to digest.
Now, the gastric wall is made up of four layers: from the outside in, there’s the adventitia, or serosa; the muscular layer; the submucosa; and the mucosa.
The mucosa comes into direct contact with food, and it also has three layers of its own.
The innermost layer is the epithelial layer and it absorbs and secretes mucus and digestive enzymes.
The middle layer is the lamina propria and it has blood, lymph vessels, and mucosa associated lymphoid tissue, or MALT for short, which are nodules of immune cells called lymphocytes, in charge of eliminating pathogens that could pass through the epithelial layer.
The outermost layer of the mucosa is the muscularis mucosa, and it’s a layer of smooth muscle that contracts and helps with the break down food.
The epithelial layer dips down below the surface of the stomach lining to form gastric pits.
And these pits are contiguous with gastric glands below which contain various epithelial cell types, each secreting a variety of substances.
So for example, foveolar cells, or surface mucus cells, secrete mucus, which is a mix of water and glycoproteins that coats the stomach epithelial cells.
With all of these digestive enzymes and hydrochloric acid floating around, the stomach and duodenal mucosa would get digested if not for this mucus which coats and protects the epithelial cells.