Pathological anatomy and classification of stomach cancer

Stomach cancer begins to develop in a small area of ​​the mucous membrane, then the thickness of the organ wall grows. In addition, the tumor grows along its wall, but mainly towards the cardia , which is due to the peculiarities of lymphatic drainage . The macro- and microscopic boundaries of the tumor almost never coincide. With an exophytic growing tumor, malignant cells are determined at a distance of 2-3 cm from the macroscopically determined border of the tumor, with infiltrative and mixed – 5-6 cm or more. The main histological form of gastric cancer is adenocarcinoma , which accounts for about 90-95% of all malignant tumors of the stomach. The second most common malignant lesion of the stomach is lymphoma . Somewhat less common are leiomyosarcoma (2%), carcinoid (1%), adenoacanthoma (1%) and squamous cell carcinoma (1%). Gastric adenocarcinomas are classified according to microscopic criteria reflecting the degree of tumor malignancy. In order of increasing degree of malignant potential, variants of adenocarcinoma can be arranged as follows: tubular, papillary, mucinous and cricoid-cell adenocarcinoma . According to the alternative histological classification of gastric cancer proposed by Lauren in 1953, they distinguish: 1. Intestinal (epidemic) type of gastric cancer, characterized by expansive growth and preservation of the glandular structure, less invasive growth and the presence of clear tumor outlines, often associated with atrophic gastritis . The intestinal Lauren gastric cancer type corresponds to Borrmann type 1 or II gastric cancer ; its development is associated with the influence of environmental factors, it has a more favorable prognosis, heredity does not affect the occurrence of this type of tumor. 2. Diffuse, or infiltrative, type (endemic), consisting of clusters of low-differentiated cells and characterized by the absence of clear contours of the tumor. The diffuse type of stomach cancer is less associated with environmental factors or diet and is more common at a young age. The emergence of a diffuse type of stomach cancer correlates with genetic factors, blood type, and heredity. To describe the macroscopic parameters of a tumor, researchers use various classification schemes for gastric cancer. In accordance with the most successful, in our opinion, classification proposed by Borrmann in 1926, all tumors of the stomach can be divided into 5 categories: type I – polypoid, or mushroom-shaped, characterized by exophytic growth in the direction of the lumen of the stomach; type II – saucer-type, characterized by exophytic growth with ulceration in the center of the tumor; type III – ulcerative-infiltrative type, characterized by ulceration of an invasively growing tumor; type IV – diffuse-infiltrative type ( linitis plastica ), characterized by diffuse damage to the walls of the stomach, with minimal damage to the mucous membrane and diffuse damage to the remaining layers of the wall of the stomach. The tumor for a long time is asymptomatic , which leads to the fact that the vast majority of patients enter the clinic in a neglected state; type V – unclassified cancer, characterized by a combination of signs of other types of tumors listed above. The increased interest in identifying early cancer in endoscopic research has led to the development of a classification based on an endoscopic macroscopic picture of the disease. The term “early cancer” is used in relation to cancer of the stomach, limited to the mucous and submucous membranes, regardless of the state of the regional lymph nodes. Early stomach cancer is divided into three groups: type I – protrusive ; type II – surface; Type III – saucer-shaped. Type II is divided into three subgroups: 1) elevated; 2) flat; 3) lowered. In Japan, over the past 20 years, the rate of detection of early stomach cancer has increased from 5 to 40%. In Western countries, early stomach cancer is detected in about 9% of cases. The location of the tumor has its own laws and prognostic significance. Cancer of the proximal stomach, sometimes with spread to the lower third of the esophagus, occurs in about 15% of cases. As noted earlier, the incidence of proximal cancer has a tendency to increase, which is especially evident in developed countries. Cancer of the body of the stomach is observed in approximately 30-35% of cases. The most common cancer of the distal stomach is 45-50% of cases. Gastric cancer is characterized by lymphogenous , hematogenous, implantation, and mixed metastasis pathways. Lesion pei of ionic lymph nodes is an example of lymphogenous metastasis and is observed in most patients. The frequency of lesions of regional lymph nodes depends on the depth of invasion by the tumor of the stomach wall. The manifestation of distant lymphogenous metastasis is metastasis to the supraclavicular lymph node, located between the legs of the left sternocleidomastoid muscle (Virchow’s node), and metastases to the ovaries ( Kruckenberg metastases ), which indicate damage to the paraortic lymphatic collector. Examples of the implantation spread of gastric cancer are peritoneal carcinomatosis , malignant ascites, peritoneal lesions of the rectum-uterine cavity ( Schnitzler metastasis ) and navel (metastasis of sister Mary Joseph). The histopathological stage of the tumor remains the most significant prognostic factor for gastric cancer. Numerous clinical trials have confirmed the decisive role of the depth of invasion by a tumor of the stomach wall and the absence or presence of metastatic lesions of regional lymph nodes or distant organs in the duration of disease-free and overall survival of patients with gastric cancer. The main goal of the international classification is the development of a uniform presentation of clinical data and the possibility of comparing treatment results. Pathological staging of gastric malignancies is performed according to the TNM system, based on three components: T – the spread of the primary tumor; N – the presence or absence of metastases in regional lymph nodes; M – the presence or absence of distant metastases. In 1997, the American Joint Committee for the Study of Cancer (AJCC) developed a classification based on the above criteria: Criterion T (primary tumor): Tx – primary tumor cannot be assessed TO – primary tumor is not determined Tis – cancer in situ , intraepithelial cancer without invasion propria mucosa ( lamina propria ) TI – tumor infiltrates own shell mucosa or submucosa T2 – tumor infiltrating the tunica muscularis or subserous layer * TK – tumor invades serosa of the stomach, but without invasion in adjacent organs T4 Tumor invades adjacent structures ** Note. * The tumor can grow the muscle layer, involving the gastrointestinal and gastrohepatic ligaments, or the greater or lesser omentum without perforation of the visceral peritoneum covering these structures. In this case, the tumor is classified as T2. If there is perforation of the visceral peritoneum covering the ligaments of the stomach or omentum, then the tumor is classified as TK. ** Neighboring structures of the stomach are the spleen, transverse colon, diaphragm, liver, pancreas, abdominal wall, adrenal glands, kidneys, small intestine, retroperitoneal space. Intrapartum spread to the duodenum or esophagus is classified by the greatest depth of invasion at all locations, including the stomach. Criterion N (state of regional lymph nodes) The perigastric lymph nodes located along the lesser and greater curvatures, as well as along the left gastric, common hepatic, hepatoduodenal , splenic and celiac arteries , are regional for gastric cancer . Paracardial lymph nodes, as well as lymph nodes along the left gastric, celiac arteries, diaphragmatic, lower mediastinal and peresophageal lymph nodes, are regional for cancer of the cardioesophageal transition . Lesions of other intraperitoneal lymph nodes are regarded as distant metastases. Nx – insufficient data to assess regional lymph nodes N0 – no signs of metastatic lesions of regional lymph nodes N1 – metastases in 1-6 regional lymph nodes N2 – metastases in 7-15 regional lymph nodes N3 – metastases in more than 15 regional lymph nodes nodes criterion M (distant metastasis) Mx – insufficient data to determine distant metastases MO – there are no signs of distant metastases M1 – distant metastases Waters it perfect in terms of the integrals ii morphological studies performed at all stages of treatment of the patient and determining the stage of the disease, a classification proposed by the Japanese Association for the Study of gastric cancer (JCGC) in 1998 g. staging does not change after the first determination and is divided into the following types: 1) clinical – s; 2) surgical – s; 3) morphological – p; 4) final – f. In addition to the characteristics of the primary tumor depending on the depth of invasion (criterion T), gastric cancer is also described depending on the location. The stomach is divided into sodium parts: the upper (U), middle (M) and lower (L) third of the stomach. If the tumor involves more than 1/3 of the stomach, then the third is indicated first, in which the bulk of the tumor is located. In accordance with the cross section of the stomach, the tumor of the stomach can be located on the front ( ant ) or back ( post ) wall, small ( less ) or large ( gre ) curvature. According to the classification proposed by JCGC, the gradation of regional lymph nodes is built depending on the localization of the pathological focus. Such a system of lymph node groups based on research to explore ways of lymph in gastric cancer of different locations, as well as data survives – gi according to defeat each group of lymph nodes. According to the JCGC classification, metastatic damage to the lymph nodes takes place in three stages. At the first stage, perigastric lymph nodes located in the ligaments of the stomach are affected . These include: 1) right paracardial lymph nodes; 2) left paracardial lymph nodes; 3) lymph nodes of the lesser curvature of the stomach; 4) lymph nodes of the greater curvature of the stomach; 5) suprapiloric lymph nodes; 6) subpiloric lymph nodes. The lymph nodes of the second stage of metastasis include lymph nodes located along the celiac trunk and its branches, the common hepatic, left gastric, splenic arteries, as well as in the gates of the spleen. The second stage groups include: 1) lymph nodes along the left gastric artery; 2) lymph nodes along the common hepatic artery; 3) lymph nodes around the celiac trunk; 4) lymph nodes in the gate of the spleen; 5) lymph nodes along the splenic artery; 6) lymph nodes of the hepatoduodenal ligament. Different groups of lymph nodes, even groups belonging to the first stage of lymphogenous metastasis, can be considered as the next stage of metastasis or as a manifestation of distant metastasis depending on the location of the tumor in the stomach. Thus, metastatic lesion of the left paracardial lymph nodes (group No. 2) in cancer of the lower third of the stomach is regarded as distant metastasis.

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