Colorectal cancer (colorectal cancer) is a common malignant tumor, accounting for the second most common cancer in the digestive system. The growth of colorectal cancer is slow, and the clinical symptoms indicate that the tumor has been growing for a long time. The early symptoms lack specificity, so it is not easy to attract attention. At the earliest stage, there can be abdominal distension, discomfort and indigestion-like symptoms, and then there will be changes in bowel habits, such as increased stools, diarrhea or constipation, and abdominal pain before stool. Later on, mucus stool or mucopurulent blood stool may appear. Due to blood loss and toxin absorption of tumor ulceration, patients often have anemia, low fever, weakness, emaciation, swelling and other manifestations, among which anemia and emaciation are especially important. In the middle and late stage, intestinal obstruction may appear, such as incomplete or complete low level intestinal obstruction, such as abdominal distension, abdominal pain (distension or colic), constipation or stool closure. On physical examination, we can see abdominal bulge, intestinal shape, localized pressure pain, and can hear hyperactive bowel sounds. Sometimes, we can find abdominal masses, which are tumor or masses bonded with omentum and surrounding tissue infiltration, hard, irregular in shape, and some can have certain mobility with intestinal tube. In order to detect colorectal cancer at an early stage, it is necessary to pay attention to alerting suspicious symptoms, especially patients with blood in stool should not think that they have hemorrhoids and delay the diagnosis. Close follow-up is needed for high-risk groups such as family history, rectal finger examination or full colonoscopy should be performed for suspicious cases, and pathological examination should be taken to obtain a clear diagnosis.
Pathological diagnosis, staging and metastasis.
(a) General staging.
(1) Mass type (cauliflower type, soft cancer) Tumor grows into the intestinal cavity, with large tumor body, hemispherical or spherical elevation, easy to ulcerate and bleed and secondary infection and necrosis. Most of the tumors of this type are highly differentiated, less invasive, slower growing, and more likely to occur in the right hemicolectomy.
2.invasive type (narrowing type, hard carcinoma) The tumor invades around the intestinal wall, has significant fibrous tissue reaction, grows along the submucosa, has a hard texture, and easily causes intestinal lumen narrowing and obstruction. This type of tumor is less differentiated, more malignant and has early metastasis. It is more likely to occur in the large intestine far from the right hemicolectum.
3.Ulcer type Tumor grows deep into the intestinal wall and infiltrates outside the intestinal wall, ulcers can appear at an early stage, with elevated edges and deep bottom, easy to bleed and infection, and easy to penetrate the intestinal wall. It has low cell differentiation and early metastasis. It is the most common type of colorectal cancer, which is usually found in the left half of the colon and rectum.
(II) Histological classification
Most colon cancers are adenocarcinomas, accounting for about three quarters. Adenocarcinoma cells are recognizable and arranged in adenoid or alveolar shape, and can be classified into three levels according to their differentiation, with grade III being the least differentiated and cells arranged in sheets or cords.
Mucinous carcinoma: The cancer cells secrete mucus, and the nucleus can be squeezed to one side within the cells (resembling a ring, some call it indolent cell carcinoma), and there is mucus and fibrous tissue reaction in the interstitium outside the cells. The differentiation is low, and it is worse than adenocarcinoma.
3.Undifferentiated carcinoma: The cancer cells are small, irregular in shape and arrangement, easily invade small blood vessels and lymphatic vessels, and infiltrate obviously. The differentiation is very low and the posterior outcome is the worst.
(C) Clinical stage
Stage I (Dukes A stage): cancer is confined to the intestinal wall
Stage A0: cancer is confined to mucosa
Stage A1: cancer is confined to the submucosa
Stage A2: cancer invaded the muscle layer of intestinal wall and did not penetrate the plasma membrane
Stage III (Dukes stage C): with lymphatic gland metastasis
Stage C1: proximal lymphatic metastasis (parietal intestine)
Stage C2: distant lymphatic metastasis (mesentery)
Stage IV (Dukes stage D): distant metastases
(IV) Diffusion and metastasis
1.Characteristics of colorectal cancer diffusion Generally, it invades in a circular pattern along the transverse axis of intestinal tube and develops deeper into the intestinal wall, while diffusion up and down along the longitudinal axis is slower, and the involved intestinal segment generally does not exceed 10 centimeters. After the cancer invades the plasma membrane, it often adheres to the surrounding tissues, adjacent organs and peritoneum.
Lymphatic metastasis of colon cancer generally spreads from near to far according to the following order, but there are also metastases across the order.
(1) Colonic lymph nodes are located in the fatty lobe of the intestinal wall.
(2) Paracolonic lymph nodes located in the mesentery adjacent to the colon wall.
(3) Mesenteric vascular lymph nodes are located in the middle of the mesentery of the colon next to the blood vessels, also called the intermediate lymph node group.
(4) Lymph nodes at the root of the mesentery Located at the root of the mesentery of the colon.
The chance of lymphatic metastasis increases after the cancer invades the muscle layer of intestinal wall, and the chance of lymphatic metastasis is even greater if the subplasma lymphatic vessels are invaded.
3.Bloodstream metastasis Generally, cancer cells or cancer emboli along the portal vein system reach the liver first, and then other tissues and organs such as lung, brain and bone. However, it can also be caused by pressing the tumor during physical examination, squeezing the tumor during surgery, or even the strong peristalsis during obstruction can prompt the cancer cells to enter the bloodstream.
4.Infiltration and implantation Cancer can directly infiltrate the surrounding tissues and organs. If cancer cells are shed in the intestinal cavity, they can be planted on other mucosa, and if they are shed in the peritoneal cavity, they can be planted on the peritoneum. The metastases are nodular or corn-like, white or grayish, hard. If it spreads to the whole abdominal cavity, it may cause cancerous peritonitis and ascites, etc.
There is no effective drug to prevent the occurrence of colorectal cancer. Once colorectal cancer is diagnosed, radical surgery is the most effective method. The effect of surgical treatment of colorectal cancer is closely related to the early and late detection of cancer, and the five-year survival rate of limited colorectal cancer can be over 90% after radical surgery. There are two kinds of surgical treatment methods: traditional open surgery and minimally invasive surgery, the former has long incision, big trauma and slow recovery. Minimally invasive surgery takes advantage of laparoscopic surgery, which gives patients another treatment option and brings blessings to them.
I. Right hemicolectomy: It is suitable for cancers of cecum, ascending colon and hepatic flexure of colon. The resection area: 15-20 cm of the end of ileum, the right half of cecum, ascending colon and transverse colon, together with the attached mesentery and lymph nodes. The cancer of the hepatic flexure also requires resection of the large part of the transverse colon and the lymph nodes of the right artery of the gastric omentum. After resection, end-to-end anastomosis or end-to-side anastomosis of ileo- and left half of transverse colon (suture closure of colonic section) is performed.
Transverse colectomy: Applicable to transverse colon cancer. Scope of resection: transverse colon and its hepatic flexure and splenic flexure. After resection, end-to-end anastomosis of ascending and descending colon is performed. If the anastomotic tension is too large, right hemicolectomy can be added to make ileo-colonic anastomosis.
Left hemicolectomy: It is suitable for cancer of descending colon and splenic flexure of colon. The scope of resection: left half of transverse colon, descending colon, part or all of sigmoid colon, together with the attached mesentery and lymph nodes. After resection, the colon and the colon or the colon and the rectum should be anastomosed end to end.
Radical resection of sigmoid colon cancer According to the specific location of the cancer, in addition to resection of the sigmoid colon, or do descending colon resection or partial rectal resection. To make colo-colonic or colo-rectal anastomosis.
Sigmoid colon cancer resection
V. Transabdominal rectal cancer resection (Dixon surgery): it is the most applied radical rectal cancer surgery at present. Recent studies have found that rectal cancer rarely infiltrates downward more than 2 cm, so the lower cut edge is required to be 3 cm from the lower edge of the tumor. With the widespread use of rectal anastomosis, most of the rectal cancer resected from the anal verge 6 can be successfully anastomosed at a super low level, which expands the indications for rectal cancer anus-preserving resection and improves the rate of anus preservation.
Combined abdominal perineal radical surgery for rectal cancer (Miles surgery): it is suitable for cancer of the anal canal and lower rectum (the lower edge of the cancer is within 6cm from the anal edge), or patients with anal incontinence and constipation with outlet obstruction. The scope of resection includes the distal sigmoid colon, the entire rectum, the inferior mesenteric artery and its regional lymph nodes, the entire rectal mesentery, the anal levator, the fat in the sciatic rectal fossa, the anal canal and about 3-5 cm of the perianal skin, subcutaneous tissue and the entire anal sphincter, and a permanent single-lumen sigmoid stoma (artificial anus) is performed in the left lower abdomen. Now there are special artificial anal pouches, which are easy to care for and do not affect social and work life.
Local excision: It is suitable for early stage rectal cancer with small tumor, limited to mucosa or submucosa and high degree of differentiation. The main surgical methods are transanal local excision and post-sacral pathway local excision, and enteroscopic mucosal dissection (ESD) is also feasible for those limited to mucosa.
Laparoscopic radical surgery for colorectal cancer: With the improvement of laparoscopic technology and the improvement of instruments, laparoscopic resection for rectal cancer is developing continuously. Laparoscopic colorectal surgery is to separate the intestinal canal, clear the lymph and remove the tumor through the operation of instruments under the television monitor. The application of ultrasonic knife makes the trauma rarely bleed. The follow-up of large number of foreign cases shows that laparoscopy and traditional surgery are reported to be better than traditional surgery in terms of tumor recurrence, distant metastasis, and five-year survival rate. It is less invasive, smaller incision, aesthetic, less postoperative pain, less surgical emergency response, often no or less painkiller application, quicker recovery, early feeding, general exhaustion and removal of gastric tube on the first postoperative day, low postoperative complication rate, and more importantly, it buys precious time for patients’ follow-up treatment (chemotherapy, radiotherapy, biotherapy, etc.). It is being welcomed by patients and families. It is suitable for colorectal cancer whose cancer is located in various sites.