Colorectal polyp (a clinical term, no pathological significance) is any tissue mass that starts from the intestinal wall and protrudes into the intestinal cavity. Polyps may be sessile or pedicled, and their sizes vary greatly. According to histology, these lesions can be divided into: tubular adenoma, tubular villous adenoma (villary adenoid polyp), villi (papilla), adenoma (with or without adenocarcinoma), hyperplastic polyp, hamartoma, Juvenile polyps, polypoid carcinomas, pseudopolyps, lipomas, leiomyomas or other rare tumors.
Colon and rectal polyps
The incidence of polyps is between 7% and 50%, and the higher numbers include very small polyps (often hyperplastic polyps or adenomas) found during autopsy. Conventional barium enema can find polyps in about 5% of patients, and more cases can be found through flexible fiber sigmoidoscopy, colonoscopy, or double-contrast air-barium enema. Polyps tend to be multiple, most common in the rectum and sigmoid colon, the closer to the cecum, the lower the frequency. In colorectal cancer patients, about 25% also have satellite adenomatous polyps.
The risk of canceration of tubular adenomas is controversial, but there is a lot of evidence that they may become malignant. The risk of malignant transformation is related to its size: a tubular adenoma with a diameter of 1.5 cm has a 2% risk of canceration. As its size increases, the glands will appear as villi. Once >50% of the glands are villous, they are called villous adenoid polyps; their malignancy may still be the same as tubular adenomas, if >80% of the glands are villous, they are called villous glands Tumors, malignant transformation occurs in about 35% of cases. The risk of malignant transformation of villous adenoma is much greater than that of tubular adenoma of the same size.
Symptoms, signs and diagnosis
Most polyps are asymptomatic. Rectal bleeding is the most common complaint. Cramps, abdominal pain, or obstruction may be signs of large lesions. Occasionally, polyps with a long pedicle may protrude from the anus. Large villous adenomas may cause massive watery diarrhea and may lead to hypokalemia.
Rectal polyps may be palpable through digital anal examination, but are often found by endoscopy. Because polyps are generally multiple and may coexist with cancer, a comprehensive colonoscopy must be performed on the entire colon, even if the lesion has been found through a flexible sigmoidoscopy. In the barium enema X-ray examination, the polyp was a round filling defect. Double contrast (colon inflation) examination is of great value, but fiber colonoscopy is more reliable.
After the colonoscopy, the polyps must be completely removed with a band ligator or electrosurgical biopsy forceps; do not use electrocautery (resection band ligation or electrocautery) for patients who have not prepared the bowel, because colonic bacteria produce There is a danger of explosion of hydrogen and methane. If colonoscopy is unsuccessful, laparotomy should be considered. Large villous adenomas are highly likely to become malignant and must be completely removed.
The treatment of cancerous polyps depends on the penetration depth of the anaplastic epithelium to the polyp pedicle, the shortest distance of the endoscopic resection boundary and the degree of differentiation of the malignant tissue. If the malignant epithelium is confined to the muscular layer of the mucosa, the polyp pedicle has a clear resection boundary or the lesion is highly differentiated, endoscopic resection and close endoscopic follow-up should be sufficient. Infiltration through the muscularis mucosa can invade the lymphatic vessels and increase the possibility of lymph node metastasis. For poorly differentiated or those lesions where the boundaries of polyp pedicle resection are not clear, partial colonectomy should be performed.
After polypectomy, the timing of follow-up examinations is still controversial. Most authoritative people advocate performing colonoscopy for the entire colon twice a year (barium enema can be used if full colonoscopy is not possible) and removing newly discovered polyps. If no new polyps are found in an annual inspection for 2 consecutive years, colonoscopy shall be performed every 2 to 3 years.
A heterozygous autosomal dominant colonic disease in which 100 or more adenomatous polyps can be found throughout the colon and rectum.
A mutated dominant gene (FAP) on the long arm of autosome 5 is the causative factor. Without treatment, almost all patients will develop malignant changes before the age of 40. Total rectocolectomy can eliminate this danger, but because the polyps of the rectum often degenerate after abdominal colectomy plus ileo-rectal anastomosis, many authorities advocate this operation first. After subtotal colonectomy, the residual rectum should be checked every 3~6m; new polyps must be removed or electrocautery. If new polyps appear too quickly and too many faces cannot be removed, the rectum must be removed and a permanent ileostomy should be performed. Patients with this disease and their families must be followed up and genetic counseling.
Gardner syndrome is a variant of familial polyposis, accompanied by desmoid tumors, skull or mandibular osteoma, and sebaceous gland cysts. Other less common variants of familial polyposis include multiple colonic adenomas and other lesions.
Peutz-Jeghers syndrome is an autosomal dominant hereditary disease in which multiple hamartomatous polyps occur in the stomach, small intestine, and colon. Symptoms include melanin deposits on the skin and mucous membranes, especially on the lips and gums.
Juvenile polyps are usually non-neoplastic, their growth rate often exceeds the blood supply, and they will be cut off during adolescence. Surgery is only required when uncontrollable bleeding or intussusception occurs. Hyperplastic polyps are also non-neoplastic and often occur in the colon and rectum. Inflammatory polyps and pseudopolyps occur in chronic ulcerative colitis and Crohn's disease of the colon.
Among the new cancers that occur each year in Western countries, colorectal cancer accounts for an increasing proportion, and the incidence is second only to lung cancer. Approximately 75,000 people died of colorectal cancer in the United States in 1989, of which about 70% were in the rectum and sigmoid colon, and 95% were adenocarcinoma. Colorectal cancer is the most common cause of death among malignant tumors invading internal organs. The incidence rate begins to rise at the age of 40 and reaches a peak at the age of 60 to 75. Colon cancer is more common in women, while rectal cancer is more common in men. Synchronous tumors (more than one) can occur in 5% of patients.
The genetic susceptibility of colorectal cancer is not obvious, but there are reports of "cancer family" and "colon cancer family" (such as familial polyposis, Lynch syndrome); in these families, colorectal cancer can occur in several generations. It often occurs before the age of 40 and is more common in the right colon. In some cases of Lynch syndrome, at least four genes in autosomes 2, 3, and 7 have mutations. Other predisposing factors include chronic ulcerative colitis, granulomatous colitis and familial polyposis (including Gardner syndrome); when suffering from these diseases, the risk of canceration and the age of onset and underlying diseases at any given time The course of the disease is related.
People with a high incidence of colorectal cancer eat less fiber and more animal protein, fat and refined carbohydrates. Although carcinogens may be ingested through diet, they are more likely to come from ingested food, bile or small intestinal secretions, produced through the action of bacteria. The exact carcinogenic mechanism is unclear.
Colorectal cancer can spread directly by penetrating the intestinal wall, blood-borne metastasis, local lymph node metastasis, perineural spread and intra-intestinal metastasis.
Symptoms, signs and diagnosis
Adenocarcinoma of the colon and rectum grows slowly, and it takes a relatively long time before it reaches a larger volume to produce symptoms. Early diagnosis relies on routine examinations. The occurrence of symptoms depends on the location, type, extent and complications of the lesion. The diameter of the right colon is large, the intestinal wall is thin, and because its contents are liquid, obstruction occurs in the late stage; cancer often grows like mushrooms, the tumor may grow very large, and can even be palpated through the abdominal wall. Occult bleeding often occurs, and fatigue and weakness caused by severe anemia may be the only main complaint. The lumen of the left colon is small, the stool is semi-solid, and the cancer tends to grow around the intestinal wall, which causes constipation and increased defecation frequency or diarrhea alternately, accompanied by partial obstruction and complete abdominal cramps Obstruction may be the main manifestation of the disease, the stool may be thin strips or mixed with blood. The most common main symptom of rectal cancer is blood in the stool. When bleeding occurs in the rectum, even if it is accompanied by obvious hemorrhoids or known diverticulosis, the possibility of simultaneous cancer must be ruled out. Rectal cancer may cause tenesmus or incomplete defecation. Before the tissues around the rectum were invaded, there was no obvious pain.
A simple, low-cost stool occult blood test is desirable as part of a program to screen and monitor high-risk groups. In order to ensure the accuracy of the results, the patient should consume a high-fiber, meat-free diet three days before the stool sampling, and further examinations are required if it is positive.
About 65% of colorectal cancers occur within the scope of the flexible fiber sigmoidoscopy. When cancer and colon-related symptoms are suspected in any part of the intestine, fiber colonoscopy should be performed. If a sigmoidoscopy reveals a lesion, then a full colonoscopy should be performed and all lesions in the colon should be completely removed. Removal of concurrent polyps under colonoscopy can reduce the number of bowel segments that need to be removed. Partial biopsy of polyps under endoscopy may have a 25% chance of misdiagnosis, and a negative biopsy does not completely rule out the possibility of cancer in polyps. If the lesion is sessile or cannot be removed under colonoscopy, surgical resection should be actively considered.
Barium enema X-ray examination is not reliable for detecting rectal cancer, but it is a very important first step in the diagnosis of colon cancer. Air-contrast X-ray examination may find smaller lesions (<6mm) than simple barium enema, but the inflatable colon may miss larger lesions (>2cm), and the missed diagnosis rate is surprising (20%~30%).The most important factor in performing barium enema and endoscopy on the colon is adequate bowel preparation, which often requires laxatives, oral enteric laxatives, and multiple enemas. If obstructive colon disease is suspected, oral administration of barium is forbidden, because the colon absorbs the water in the barium suspension, which may precipitate barium sulfate, resulting in complete colorectal obstruction. Even when the X-ray diagnosis is quite certain, colonoscopy should be performed; barium enema can miss 30% of tumors and 40% of polyps, while colonoscopy can detect coexisting lesions and can decide to remove the intestinal segment length.
Elevated serum carcinoembryonic antigen (CEA) has no specific relationship with colorectal cancer, but the level of CEA is elevated in 70% of patients. If the level of CEA increases before surgery but decreases after tumor resection, monitoring of CEA may help to find the recurrence of the disease. CA19-9 and CA125 are other tumor markers that may also be elevated.
Treatment and prognosis
The basic treatment of colon cancer is to perform extensive surgical resection of the colon cancer lesion and its local lymphatic drainage area after preparing the bowel. The choice of surgical methods for rectal cancer depends on the distance between the lesion and the anus and the scope of sight. Abdominal resection of the rectum requires permanent sigmoid colostomy. Low anterior resection with sigmoid colon and rectal anastomosis can be used as the preferred treatment only in the following situations: that is, the normal intestinal segment 5cm below the lesion can be removed, and this operation is technically feasible. The use of a stapler (Stapler) can make more patients' low anterior resection and anastomosis closer to the rectum without harming their rectum.
Surgery may cure 70% of patients. If the cancer is confined to the mucosa, the best 5-year survival rate can be close to 90%; if colon cancer has penetrated the muscularis propria, the survival rate is about 80%; if it has metastasized to the lymph nodes, it is 30%. If the patient cannot bear the risk of surgery, some colon cancers can be locally controlled by electrocoagulation. Preliminary research results show that supplemented with radiotherapy after radical rectal cancer (rather than colon cancer) surgery can control the growth of local tumors in patients with limited lymph node involvement, delay cancer recurrence, and improve survival.
There is controversy about preoperative radiotherapy to improve the resection rate of rectal cancer; experts have different opinions on whether this treatment will increase the chance of surgery or affect the detection of local lymph node metastasis. A controlled study of preoperative and postoperative chemotherapy combined with radiotherapy has been carried out on patients with rectal cancer.
Appropriate controlled studies have found that the efficacy of 5-FU combined with levamisole or folinic acid as an adjuvant surgical treatment in patients with colon cancer with positive lymph nodes (stage III, Dukes stage) has not been determined.
There is still debate about the length of follow-up after radical surgery for colorectal cancer. Most authorities advocate that colonoscopy or X-ray examination should be carried out once a year for the residual intestines for 2 consecutive years. If the result of the examination is negative, it should be rechecked every 2 to 3 years thereafter.
If radical surgery is not possible, limited palliative surgery may be required, with a median survival of 7 months. The only proven effective drug for advanced colorectal cancer is 5-FU, but only 15% to 20% of patients receiving this treatment have been confirmed to have tumor shrinkage and prolonged survival. The commonly used 5-FU treatment regimen requires administration for 5 days every 4 to 5 weeks, but this treatment should not be given if the doctor is not familiar with the dangers of chemotherapy drugs and the lowest point of blood cell count. Although some oncologists believe that the combination of 5-FU and leucovorin is superior to 5-FU alone, other drugs used alone or in combination with 5-FU are usually not proven to have a good effect. A new drug, irinotecan (camptosar), can also be used alone for patients with advanced colon cancer. It has been used as part of combined chemotherapy to evaluate the treatment plan. However, chemotherapy for patients with advanced colon cancer should be applied under the guidance of experienced chemotherapy experts.
When the metastasis is confined to the liver, 5-FU or radioactive microspheres can be injected into the hepatic artery through an implanted subcutaneous pump or an external pump mounted on a waist belt, and the patient can take the pump to walk around; this perfusion therapy is more effective than systemic chemotherapy It may be better, but these hepatic artery infusion therapies are expensive and their value needs to be confirmed in clinical studies. If metastasis occurs outside the liver, the hepatic artery enema chemotherapy with perfusion pump is not superior to systemic chemotherapy.
The most common anorectal cancer is adenocarcinoma. Other tumors include squamous genital cavity protocarcinoma, melanoma, lymphoma and various sarcomas. Anorectal epidermoid (non-keratinous squamous cell or basal cell) carcinoma accounts for 3% to 5% of distal colorectal cancer. Chronic fistula, anal skin radiation, mucosal leukoplakia, venereal lymphogranuloma, Bowen disease (carcinoma in the dermis) and condyloma acuminatum are their precancerous lesions, which have been confirmed to be mainly related to human papilloma virus infection. The tumor has metastasized along the rectal lymph node ducts and inguinal lymph nodes. Basal cell carcinoma, Bowen disease (carcinoma in the dermis), Paget disease outside the breast, genital cavity protocarcinoma and malignant melanoma are less common.
The effect of local extensive resection in the treatment of perianal cancer is often satisfactory. The combination of chemotherapy and radiotherapy has a high cure rate for anal squamous tumors and keratinous tumors. If radiotherapy and chemotherapy cannot completely shrink the tumor, the abdominal perineum should be removed.
Pathogenesis of colorectal cancer
Pathogenesis Colorectal cancer can occur in any part from the cecum to the rectum. In China, the incidence of left colon is high, but there are also reports that the incidence of right colon cancer is higher in women in high-incidence areas. According to the statistics of 3147 cases of colorectal cancer by the China Colorectal Cancer Pathology Research Group (NCG), left colon cancers below and below the splenic flexure accounted for 82.0% of all colorectal cancers, of which rectal cancer has the highest incidence, accounting for 66.9% is significantly higher than Europe, America and Japan, where rectal cancer only accounts for 35% to 48% of colorectal cancer. Colorectal cancers of other intestinal segments are sigmoid colon (10.8%), cecum (6.5%), ascending colon (5.4%), transverse colon (3.5%), descending colon (3.4%), hepatic flexure (2.7%), splenic flexure ( 0.9%).
Intestinal cancer can be divided into early cancer and advanced cancer according to the depth of tumor involvement. Early cancer is limited to the large intestine mucosa or submucosa without lymph node metastasis.
1. General type
(1) Early cancer:
①The raised polyp type (type I) can be divided into pedicle type (IP)), sub-pedicle type (IS) or broad base type. This type is also mostly intramucosal carcinoma.
② Flat type: This type is mostly intramucosal cancer.
③The flat bulge type (Ⅱa) is roughly coin-shaped. This type mostly involves the submucosa.
④The flat raised ulcer type (Ⅱa+Ⅱc) is roughly like a small disc with raised edges and sunken center. This type involves the submucosa.
(2) Middle and late stage colorectal cancer: For a long time, the general classification of colorectal cancer has been confused. In 1982, the Chinese Colorectal Cancer Pathology Research Cooperative Group made systematic and detailed observations on surgical specimens of colorectal cancer, and proposed to divide colorectal cancer into 4 types. It was adopted by the National Anti-Cancer Association in 1991.
① Protruding type: All tumors protruding into the intestinal cavity belong to this type. The tumor can be nodular, polypoid, or cauliflower-like bulge, with a clear boundary, pedicle or broad base. The boundary between the tumor and the surrounding tissues on the cut surface is often clear, and the infiltration is relatively superficial and limited. If the surface of the tumor becomes necrotic and falls off, ulcers can form.
②Ulcer type: is the most common general type. A deeper ulcer is formed in the center of this type of tumor, and the bottom of the ulcer reaches or exceeds the muscle layer. According to the appearance and growth of the ulcer, it can be divided into the following two subtypes:
A. Limited ulcer type: The ulcer has a crater-like appearance, with a central necrotic depression, forming an irregular ulcer. The edge of the ulcer is a dike-like tumor tissue protruding on the surface of the intestinal mucosa.
B. Infiltrating ulcer type: This type of ulcer looks like a gastric ulcer. The tumor mainly infiltrates into the intestinal wall to thicken the intestinal wall, and then the center of the tumor necrosis and falls off to form a depressed ulcer. Around the ulcer is the tumor tissue covering the intestinal mucosa, which is slightly ramp-shaped. On the cut surface, the boundary of the tumor tissue is unclear. If the ulcer is deep, the local muscle layer can disappear completely.
③Invasive type: This type of tumor is characterized by infiltrating growth into all layers of the intestinal wall. The intestinal wall of the lesion is thickened, and the surface mucosal folds are thickened, irregular or disappeared and flattened. There are no ulcers in the early stage, and superficial ulcers may appear in the later stage.
④ Gel-like type: When a large amount of mucus is formed in the tumor tissue, the cross-section of the tumor may be translucent and gel-like, which is called gel-like type. This type is seen in mucinous adenocarcinoma. The gel-like type has different appearances, which can be uplifted and massive, and can also form ulcers or mainly infiltrate.
7 high-risk factors for colorectal cancer
In the 1970s, about 10 out of 100,000 people suffered from colorectal cancer. Since then, it has been increasing at a rate of 10% every year, and the incidence is even higher in economically developed areas. Can not be ignored: the incidence of colorectal cancer is rising!
Colorectal cancer and its location
The human intestine is divided into the small intestine and the large intestine, the latter includes the colon and the rectum. Cancers that grow in the rectum and colon are collectively called colorectal cancer. Among them, cancer of the left intestine (rectum, sigmoid and descending colon) accounted for 75%, cancer of the right intestine (ascending colon) accounted for 20%, and cancer of the transverse colon accounted for only 5%. The incidence of rectal cancer is the highest, accounting for about 60% of colorectal cancer.
Colorectal cancer and age of onset
The incidence of colorectal cancer is mostly in people aged 41 to 60 (the first peak period), followed by those under 40 years of age (the second peak period), and the incidence rate of people over 61 years old is lower (the third peak period). The population at the second peak of colorectal cancer is mostly concentrated in the 25 to 35 years old, so young people cannot ignore colorectal cancer.
High risk factors
1. Long-term constipation The longer the stool stays in the large intestine, the greater the adverse effect of carcinogens on the intestinal mucosa.
2. There are many reasons for long-term loose stools. One of them is colorectal polyps. If polyps are not found for a long time, they can become cancer. The longer the loose stools, the greater the need for colonoscopy.
3. The metabolites of high-protein and high-fat diets in the body can easily induce cell malignancy, which can cause colorectal cancer.
4. Long-term inflammatory bowel disease Ulcerative colitis is a type of inflammatory bowel disease, long-term improper treatment, multiple recurrence of the disease, and the disease course over 8 years should be alert to the occurrence of colorectal cancer.
5. Family history of colorectal cancer People of all ages with a family history of this disease should always pay attention to the appearance of colorectal cancer symptoms.
6. Colorectal polyps About 80% of colorectal cancers come from colorectal polyps. Patients with colorectal polyps must undergo colonoscopy regularly.
7. Hemorrhoids bleeding Some patients with hemorrhoid bleeding have polyps or cancers in the large intestine above the anus. If only bleeding symptoms are noted in the diagnosis, it is very likely that important diseases that occur in the large intestine will be missed! It is recommended that those who have hemorrhoids bleeding must go to the hospital's gastroenterology department for colonoscopy in the near future.
Clinical symptoms of colorectal cancer
When you find the following conditions, especially the first 6 items, you should go to the hospital as soon as possible for further diagnosis and enteroscopy and other related examinations.
(1) Increased stool frequency; (2) Pus and blood in the stool, blood in the stool; (3) Fecal occult blood is positive for multiple times; (4) After hemorrhoids bleeding; (5) Anemia; (6) Abdominal pain; (7) Abdominal distension; (8) Loose or loose stools and alternate constipation; (9) Inability to relieve stool; (10) Abdominal mass; (11) Loss of appetite; (12) Weight loss.
Differential diagnosis of colorectal tumors
(1) Hemorrhoids: Rectal cancer is often mistaken for hemorrhoids. Generally, internal hemorrhoids are mostly painless bleeding, which is not mixed with stool. In patients with colorectal cancer, blood in the stool is often accompanied by symptoms of mucus and rectal irritation, digital rectal examination and sigmoid colon. Microscopic examination can be used for identification.
(2) Amoebic enteritis: When the lesion develops into a chronic phase, the granulation tissue at the base of the ulcer proliferates and the surrounding fibrous hyperplasia, which thickens the intestinal wall and narrows the intestinal lumen. It is easy to be misdiagnosed as cancer. At this time, a biopsy is required.
(3) Intestinal tuberculosis: the age of onset is relatively young, and the history of tuberculosis in other organs is more common in the ileocecal area. However, proliferative intestinal tuberculosis, due to a large number of tuberculous granulomas and fibrous tissue hyperplasia, makes the intestinal wall thick and hard, which is easy to be confused with cecal cancer. Pathological biopsy is required to confirm the diagnosis. X-ray barium meal examination can find the lesions Agitation phenomenon or jumping phenomenon is helpful for diagnosis.
(4) Localized enteritis: It usually occurs in young people. It is common to have abdominal pain, diarrhea, fever, weight loss, anemia, loss of appetite, nausea, vomiting, abdominal mass and fistula formation, etc. Symptoms and signs, such as x-ray barium meal and fiber colonoscopy Identify.
(5) Chronic bacillary dysentery: Patients may present with abdominal pain, diarrhea, seldom pus and blood in the stool, mild tenesmus, after stool culture, barium enema and endoscopy, it is not difficult to make a diagnosis.
(6) Ulcerative colitis: The symptoms are quite similar to chronic bacillary dysentery, but there is a history of repeated attacks, stool culture is negative, and sigmoid colonoscopy shows fine granular changes in the mucosa, disappearance of blood vessel texture, accompanied by erythema-like congestion and small oval ulcers. Its surface is often covered with yellow-white exudate, and severe cases have large irregular ulcers.
(7) Other differential diagnosis of colorectal tumors: such as willow lymphogranuloma, rectal endometriosis, colonic diverticulitis, etc., can be identified with the help of symptoms, signs, x-ray examination and fiber enteroscopy.
Attention after colorectal cancer surgery
Colonoscopy should be performed at the time specified by the doctor after colorectal cancer surgery, because some colorectal cancer can develop cancer in other parts of the large intestine after surgery.
Types of colorectal tumors in the elderly
1. Papillary adenocarcinoma
All or most of the tumor tissue has a papillary structure. The nipple can be slender or stubby. The part where it infiltrates into the intestinal wall can often be seen protruding from the cystic gland cavity of varying sizes.
Usually the nipple has less interstitium. The epithelium covering the surface of the nipple is mostly single-layered or multi-layered, and the degree of differentiation of cancer cells varies.
2. Tubular adenocarcinoma
It is the most common histological type of colorectal cancer, accounting for 66.9%-82.1% of all colorectal cancers. Tubular adenocarcinoma is mainly characterized by the glandular tubular structure formed by the cancerous tissue. According to the differentiation and abnormality of cancer cell and duct structure, it can be divided into 3 levels:
1. Highly differentiated adenocarcinoma All or most of the cancer tissues are glandular tubular structures. Epithelial cells are more maturely differentiated, mostly in a single layer lining the glandular lumen. The nucleus is mostly located at the base, secretion in the cytoplasm, and goblet cell differentiation.
2. Moderately differentiated adenocarcinoma
Glandular structures can still be seen in most cancer tissues, but the ducts are irregular in shape and different in size and shape, or are branched; a small part of tumor cells are arranged in solid clusters or cords. Poor differentiation of cancer cells: the heteromorphism is more obvious.
When it forms a duct structure, the epithelium can be arranged in a pseudo-stratified layer, with uneven and overlapping nuclei, which can reach the top of the cytoplasm, and the cytoplasmic mucus secretion is reduced.
3. Poorly differentiated adenocarcinoma
The characteristic of this type of tubular adenocarcinoma is that the structure of the duct is not obvious, only a small part (less than 1/3) shows the structure of the duct, and the cell abnormality is more obvious.
4. Mucinous adenocarcinoma
This type of cancer is characterized by the cancer cells secreting large amounts of mucus and forming a "mucus lake". Two types are often seen in histology: one is an enlarged cyst-like glandular tubular structure with large pieces of mucus epithelium in the capsule. Some epithelium is flat due to the mucus in the capsule, and even falls off. Another histological manifestation is that there are piles of cancer cells floating in a large mucus lake, the cells are poorly differentiated, and the nucleus is large and deeply stained, which can be signet ring-shaped.
5. Signet ring cell carcinoma
The tumor is composed of diffused signet ring cells and does not form a glandular tubular structure. When there is less mucus formation in the tumor cells, the nucleus may be round and the cytoplasm may be pink and lack the characteristics of signet ring cells, but mucus staining can detect mucus in the cytoplasm.
6. Undifferentiated cancer
The cancer cells grow in diffuse or infiltrating masses, without forming ducts or other tissue structures. Cancer cells are usually small, have less cytoplasm, and are more consistent in size and shape. Sometimes they are difficult to distinguish from lymphosarcoma.
7. Small cell carcinoma
About 0.5%. Cancer cells are small and slightly larger than lymphocytes. Cancer cells are often arranged in a dense mosaic, with few cytoplasm, round, oval, melon seed or irregular nuclei, deep stained nuclei, unclear nucleoli, and high malignancy.
8. Adenosquamous carcinoma
Also known as adenocarcinoma, adenocarcinoma and squamous cell carcinoma of this type of tumor cells are mixed. Adenocarcinoma is partially differentiated, generally well, with adenoid structure or more goblet cells and mucus secretion. The squamous cell carcinoma is generally less differentiated, and keratinization is rare.