Spread of Malignant Tumors
Tumors spread by one or more methods depending on the characteristics of the specific tumor cells. They produce secondary tumors that consist of cells identical to the primary (parent) tumor. Many cancers have already spread prior to diagnosis, and it is important to identify this activity before treatment begins. There are three basic mechanisms for spread of cancer:
- Invasion refers to local spread where the tumor cells grow into adjacent tissue, destroying normal cell (Fig.5-4). Tumor cells are loosely attached to other cells and also secrete Lytic enzymes that break down tissue. The origin of the word cancer is the Latin word meaning "crablike," a good image of an invasive tumor.
- Metastasis means spread to distant sites by blood or lymphatics. In this case, the tumor cells erode into a vein or lymphatic, travel through the body, and eventually lodge in a hospitable environment toreproduce and create one or more secondary tumors(Fig.5-5). Only a few tumor cells survive this transfer, but it only takes a few to start a new tumor. Frequently, the firstvmetastasis appears in the regional lymph nodes, which localize the tumor cells for a time. These lymph nodes are checked at the time of surgery, and often several are removed. Often, the lymph nodes are removed or treated to eradicate any micrometastases that may be missed, particularly in cancers that are known to spread at an early stage(e.g., breast cancer). Many cancers spread by normal venous and lymphatic flow, and therefore the lungs and liver are common secondary sites for many tumors(Fig.5-6). Note the large number of secondary tumors in the liver shown in this figure. However, some cancers are more selective and spread to unusual sites.
- Seeding refers to the spread of cancer cells in body fluids or along membranes, usually in body cavities. Again, the tumor cells break away and travel easily with the movement of fluid and tissue. Anexample is ovarian cancer, where the large peritoneal membrane encourages dispersion of the tumor cells throughout the peritoneal cavity (Fig.5-7). Malignant cells may also be dislodged from the tumor if excessive handling occurs during diagnostic procedures or surgery, leading tobfurther spread.
แพร่กระจายของเนื้องอกที่ร้ายแรงเนื้องอกแพร่กระจาย โดยหนึ่ง หรือหลายวิธีตามลักษณะของเซลล์เนื้องอกเฉพาะ พวกเขาผลิตรองเนื้องอกที่ประกอบด้วยเซลล์ที่เหมือนกับเนื้องอกหลัก (หลัก) มะเร็งหลายแล้วแพร่กระจายก่อนการวินิจฉัย และจะต้องระบุกิจกรรมนี้ก่อนเริ่มรักษา มีกลไกพื้นฐาน 3 การแพร่กระจายของมะเร็ง:-บุกรุกถึงแพร่กระจายเฉพาะที่เซลล์เนื้องอกเติบโตเป็นเนื้อเยื่อติดกัน ทำลายเซลล์ปกติ (Fig.5-4) เซลล์เนื้องอกซึ่งแนบกับเซลล์อื่น ๆ และยัง หลั่งเอนไซม์ Lytic ที่แบ่งเนื้อเยื่อ ต้นกำเนิดของมะเร็งคำเป็นคำละตินหมายถึง "crablike ภาพลักษณ์ที่ดีของเนื้องอกการรุกราน - Metastasis means spread to distant sites by blood or lymphatics. In this case, the tumor cells erode into a vein or lymphatic, travel through the body, and eventually lodge in a hospitable environment toreproduce and create one or more secondary tumors(Fig.5-5). Only a few tumor cells survive this transfer, but it only takes a few to start a new tumor. Frequently, the firstvmetastasis appears in the regional lymph nodes, which localize the tumor cells for a time. These lymph nodes are checked at the time of surgery, and often several are removed. Often, the lymph nodes are removed or treated to eradicate any micrometastases that may be missed, particularly in cancers that are known to spread at an early stage(e.g., breast cancer). Many cancers spread by normal venous and lymphatic flow, and therefore the lungs and liver are common secondary sites for many tumors(Fig.5-6). Note the large number of secondary tumors in the liver shown in this figure. However, some cancers are more selective and spread to unusual sites.- Seeding refers to the spread of cancer cells in body fluids or along membranes, usually in body cavities. Again, the tumor cells break away and travel easily with the movement of fluid and tissue. Anexample is ovarian cancer, where the large peritoneal membrane encourages dispersion of the tumor cells throughout the peritoneal cavity (Fig.5-7). Malignant cells may also be dislodged from the tumor if excessive handling occurs during diagnostic procedures or surgery, leading tobfurther spread.
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