Gastric cancer is one of the most common malignant tumors in digestive tract. In the statistics of malignant tumor deaths in many areas of China, gastric cancer ranks first or second. The onset age of gastric cancer is 40 ~ 60 years old. There are more men than women, and the ratio of men to women is about 3∶ 1 or 2∶ 1. The most common site is the gastric antrum, especially the small curved side (about 75%), but it is rare in the body of the stomach.
Gastric cancer can be divided into early gastric cancer and advanced gastric cancer according to its lesion and progression.
(1) Early gastric cancer
Early gastric cancer is confined to mucosa and submucosa. Therefore, the criterion for judging early gastric cancer is not its area, but its depth. So early gastric cancer is also called mucosal cancer or superficial diffuse cancer (figure 10- 10). The prognosis of early gastric cancer after surgical resection is quite good, and the 5-year survival rate after operation is 54.8% ~ 72.8%. In recent years, due to the widespread application of fiberoptic gastroscopy biopsy and exfoliative cytology, the detection rate of early gastric cancer has been significantly improved (figure10-1).
Figure 10- 10 Early gastric cancer
Canceration is confined to the gastric mucosa and does not exceed the muscularis mucosa.
Fig. 10- 1 1 exfoliated cells of early gastric cancer.
(The same picture 10- 10) Cancer cells are large, with different shapes, large nuclei and deep coloration of ×900.
The macroscopic morphology of early gastric cancer can be divided into three types (Figure 10- 12):
1. Protrusive (type I) tumor obviously protrudes from the surface of gastric mucosa, and sometimes it is polypoid.
2. Superficial type (type II) tumor has a flat surface with no obvious protuberance. This type can be subdivided into: ① superficial uplift type (Ⅱ A type) (Figure 10- 13), ② superficial flatness type (Ⅱ B type) and ③ superficial depression type (Ⅱ C type), also known as cancer erosion.
Fig. 10- 12 patterns of early gastric cancer.
M mucosa; Mm mucosal muscle; Sm submucosa; Pm muscularis; Streptococcus sera
Figure 10- 13 Early gastric cancer (superficial uplift Ⅱ A type)
There is a gastric cancer protruding from the surface with a diameter of about 1cm on the mucosa near the pylorus on the side of the small bend (arrow point).
3. Digging type (type ⅲ) has ulcer formation, and the ulcer can reach the muscularis. This type is the most common.
Histological classification: tubular adenocarcinoma is the most common, followed by papillary adenocarcinoma, and undifferentiated carcinoma is the least.
(ii) Advanced gastric cancer
If the cancer tissue infiltrates below the submucosa, it belongs to advanced gastric cancer, or middle and advanced gastric cancer. The deeper the infiltration of cancer tissue, the worse the prognosis, and the 5-year survival rate of infiltrating serosa layer is significantly lower than that of infiltrating muscular layer.
The naked eye morphology can be divided into three types:
1. Polypoid or mushroom-like cancer tissue grows to the mucosal surface, showing polypoid or mushroom-like shape and protruding into the gastric cavity (Figure 10- 14).
Fig. 10- 14 polypoid gastric cancer
The mass is polypoid and protrudes from the stomach cavity.
2. Ulcerative type, some cancer tissues are necrotic and fall off, forming ulcers. Ulcers are generally dish-shaped with some protruding edges, such as craters (Figure 10- 15).
Figure 10- 15 Ulcerative gastric cancer
The center of the mass festers, forming an ulcer with protruding edges and irregular shapes.
The difference between gastric ulcer and benign peptic ulcer is shown in table 10- 1.
Table 10- 1 Morphological Differentiation of Benign and Malignant Ulcer
Benign ulcer (ulcer disease)
Malignant ulcer (ulcerative gastric cancer)
The shape is round or oval, not plastic, dish or crater.
The diameter of large and small ulcers is generally less than 2 cm, and the diameter of ulcers is often greater than 2 cm.
There are deep and shallow.
The edges are neat, not bulging, irregular and not bulging.
The bottom is flat, with necrosis and bleeding.
The folds of the surrounding mucosa are interrupted into concentrated folds of ulcers, showing nodular hypertrophy *
* Because there is cancer tissue growing in the submucosa.
3. Invasive cancer tissue infiltrated into the stomach wall locally or diffusely, and there was no obvious boundary with the surrounding normal tissues. During diffuse infiltration, the gastric wall thickens and hardens, the gastric cavity shrinks, and most mucosal folds disappear. Typical diffuse invasive gastric cancer is called linitis plastica because its stomach looks like a small bag made of leather (Figure 10- 16).
Figure 10- 16 Diffuse and invasive gastric cancer
Due to the diffuse infiltration of cancer tissue, the gastric wall is obviously thickened.
Borrmann(B) typing is also commonly used in the general classification of advanced gastric cancer. Among them, B 1 type is uplift type, B2 type is localized ulcer type, B3 type is infiltrating ulcer type and B4 type is diffuse infiltration type.
Microscopically, according to the histological structure of cancer, advanced gastric cancer is generally divided into four histological types:
1. Adenocarcinoma is the most common. Most of the cancer cells are columnar and arranged in adenoids (figure 10- 17), and many papillae (papillary adenocarcinoma) appear in the adenoids. Some cancer cells are cubic or round, and several cancer cells form small acini. This type of cancer has high differentiation, low malignancy and late metastasis.
Figure 10- 17 Gastric adenocarcinoma
The cancer tissue showed glandular structure and spread to the stomach wall ×47.
2. Myeloid cancer cells are arranged without glands, with large cells, pleomorphism, obvious heteromorphism and high malignancy, and often infiltrate deep layers earlier.
3. The cancer cells of hard cancer are small, round or short spindle-shaped, arranged in rope shape, mostly without glandular tube-like structure, and the stroma is a lot of fibrous tissue (Figure 10- 18). This type is highly malignant.
Fig. 10- 18 gastric hard cancer
There are cancer cells infiltrating in the fibrous tissue with obvious submucosal hyperplasia, and the cancer cells are arranged in narrow strips.
Medullary cancer and hard cancer are also called solid cancer or simple cancer, because most cancer tissues have no glandular cavities and are solid structures.
4. Myxoid carcinoma is glandular or simple, and there are a lot of acidic mucus in the cytoplasm of cancer cells, which often squeezes the nucleus on one side of the cytoplasm of cancer cells in a ring shape, so it is called a signet ring cell (figure 10- 19). Mucinous cancer has a high degree of malignancy. This type of cancer is also called glial cancer, because it contains a lot of mucus and looks like translucent jelly to the naked eye.
Fig. 10- 19 mucinous carcinoma
Cancer cells are clustered, the cytoplasm is filled with a lot of mucus, and the nucleus is squeezed to one side, showing a signet ring shape.
In addition to the above classification, gastric cancer can also be divided into intestinal type and diffuse type according to the cell morphology and mucus properties in gastric cancer tissues. Sialic acid mucus and sulfuric acid mucus are more common in intestinal gastric cancer, while neutral mucus is more common in diffuse gastric cancer. Gastrointestinal cancer is more common in elderly patients, and the degree of malignancy is low. Histologically, most of them are papillary adenocarcinoma or adenoductal adenocarcinoma. Diffuse gastric cancer is more common in young people and has a high degree of malignancy. Histologically, most of them are mucinous carcinoma and undifferentiated carcinoma.
It should be pointed out that the histological structure of many gastric cancers is not a single type, and there are often two histological types in the same gastric cancer specimen. Gastric cancer occurring in cardia can be adenoacanthoma and squamous cell carcinoma, with both glandular epithelium and squamous epithelium.
Diffusion route
1. Cancer tissues that directly spread to the serosa layer of stomach can directly spread to adjacent organs and tissues, such as liver, pancreas and omentum.
2. Lymphatic metastasis is the main route of gastric cancer metastasis, which first metastasizes to local lymph nodes, among which paracoronary lymph nodes and pyloric lymph nodes on the side of gastric minor curvature are the most common. The former can further spread to lymph nodes near abdominal aorta and hilar lymph nodes and reach the liver; The latter can reach lymph nodes above the pancreatic head and at the root of mesentery. Cancer that has metastasized to lymph nodes in greater curvature of stomach can further spread to greater omentum lymph nodes. Advanced cancer cells can metastasize to supraclavicular lymph nodes through thoracic duct, and left supraclavicular lymph nodes are more common.
3. Blood metastasis is mostly in the late stage, usually through portal vein to liver, followed by lung, bone and brain.
4. Implantable metastatic gastric cancer, especially gastric mucinous cancer cells, can fall off to the abdominal cavity after infiltrating into the gastric serosa and be planted in the abdominal wall and peritoneal cavity of pelvic organs. Metastatic mucinous carcinoma sometimes forms in the ovary, called Krukenberg tumor.
Histogenesis of gastric cancer
1. The cellular origin of gastric cancer Inferred from the morphological study of early micro-gastric cancer, gastric cancer mainly occurred in stem cells of gastric gland and neck. The regeneration and repair of glandular epithelium is particularly active here, which can differentiate into gastric epithelium and intestinal epithelium, and canceration often begins from this part.
2. Intestinal metaplasia and canceration In early gastric cancer samples, the phenomenon of intestinal metaplasia (large intestine type) changing to gastrointestinal cancer can be observed. The detection rate of metaplasia in large intestine of mucosa adjacent to gastric cancer can often reach 88.2%. Some people speculate that the carcinogenesis mechanism may be due to the enhanced absorption of carcinogens by these intestinal metaplastic cells, and the existence of highly active aminopeptidase in the cytoplasm of intestinal metaplastic cells and cancer cells, but not in normal gastric mucosa. This variation is likely to form the basis of canceration.
3. Atypical hyperplasia and malignant gastric cancer, severe atypical hyperplasia often occurs near cancer, and some of them have a transitional relationship with canceration. At present, it is considered that severe atypical hyperplasia is a precancerous lesion with canceration potential.
The cause of disease
It is still unknown. The occurrence of human gastric cancer has certain geographical distribution characteristics. For example, the incidence rates in Japan, China, Iceland, Chile and Finland are much higher than those in the United States and western European countries. This may be related to the eating habits of various countries and nationalities and the soil geological factors in various regions. According to the survey, the occurrence of gastric cancer is related to eating a large number of smoked foods such as fish and meat. Feeding animals food contaminated with aflatoxin or containing nitrite can also induce gastric cancer. Some people in Japan have suggested that the high incidence of gastric cancer is related to the treatment of meals eaten by residents with talcum powder. Because talcum powder contains asbestos fiber with carcinogenic effect. In recent years, due to the change of Japanese eating habits, the incidence of gastric cancer has a downward trend.
Other tumors
Gastrointestinal leiomyoma is another site that is prone to leiomyoma besides uterus. Among them, stomach is the most, followed by small intestine. This kind of tumor can often protrude into the gastrointestinal cavity, or a huge lump can protrude into the serosa, which will not cause gastrointestinal symptoms. The tumor tissue is composed of interwoven fascicular smooth muscle cells with long protrusions at both ends, blunt nuclei and occasional round or polygonal cells. If the tumor cells are atypical or odd smooth muscle cells, they are called leiomyoblastoma. Histologically, it is difficult to distinguish leiomyoma from smooth myoblastoma. Although the latter has atypical hyperplasia of tumor cells, it cannot be regarded as malignant. Malignant leiomyosarcoma is characterized by polymorphous nuclei of most tumors, which may have giant cells with strange shapes. More mitotic images are often indications of malignancy. Leiomyosarcoma is often transferred from blood, or it can directly infiltrate and spread to the peritoneal surface.
Malignant lymphoma The most common malignant lymphoma outside lymph nodes occurs in the stomach, followed by the intestine. Primary gastric malignant lymphoma is difficult to differentiate from gastric cancer in clinic. The 5-year survival rate of this tumor is higher than that of gastric cancer. In appearance, it is often flat and disc-shaped with clear edges. Sometimes it is difficult for the naked eye to distinguish it from cancer.