Colorectal tumor
A colorectal polyp (a clinical term with no pathological significance) is any mass of tissue that originates from the intestinal wall and protrudes into the intestinal lumen. Polyps may be non-tipped or tipped, and their size varies widely. According to histology, these lesions can be classified as: tubular adenoma, tubular villous adenoma (villous adenoid polyp), villous (papilla), adenoma (with or without adenocarcinoma), hyperplastic polyp, misshapen polyp, juvenile polyp, polypoid carcinoma, pseudopolyps, lipoma, smooth muscle tumor or other rarer tumors. Min Chunming, Department of Anorectal Surgery, Shiyan People’s Hospital
Colon and rectal polyps
Brief introduction
The incidence of polyps ranges from 7% to 50%, with the higher number including very small polyps (often hyperplastic polyps or adenomas) found at autopsy. Routine barium enemas can detect polyps in about 5% of patients, while more cases can be detected by curvilinear fiberoptic sigmoidoscopy, colonoscopy, or double contrast air-barium enemas. Polyps tend to be multiple, occurring most commonly in the rectum and sigmoid colon and less frequently the closer to the cecum. Satellite adenomatous polyps are also found in about 25% of patients with colorectal cancer.
Carcinogenic risk
The risk of carcinoma in tubular adenomas is controversial, but substantial evidence suggests that they may be malignant. The risk of malignancy is related to their size: tubular adenomas of 1. 5 cm in diameter have a 2% risk of carcinogenesis, and as they increase in size, the glands develop a choroidal appearance. Once >50% of the glands are villous, they are called villous adenoid polyps; their malignant potential remains the same as that of tubular adenomas, and if >80% of the glands are villous, they are called villous adenomas, which will become malignant in about 35% of cases. The risk of malignancy is much greater in villous adenomas than in ductal adenomas of equivalent size.
Signs, symptoms and diagnosis
Most polyps are asymptomatic. Rectal bleeding is the most common complaint. Painful cramping, abdominal pain, or obstruction may be signs of a large lesion. Occasionally polyps with long tips may prolapse from the anus. Large villous adenomas may cause massive watery diarrhea and may lead to hypokalemia.
Rectal polyps may be palpated by anal fingering, but are often detected by endoscopy. Because polyps are usually multiple and may coexist with cancer, a full colonoscopy of the entire colon is necessary, even if the lesion has been detected by curvilinear sigmoidoscopy. On barium enema x-ray, polyps appear as round filling defects. Double contrast (colon inflation) examination is of great value, but fiberoptic colonoscopy is more reliable.
Treatment
After total colonoscopy, polyps must be completely removed with a ligature or electrosurgical biopsy forceps; electrocautery (excisional ligation or electrocautery) should never be used in patients without bowel preparation because of the risk of explosion of hydrogen and methane produced by colonic bacteria. If resection by colonoscopy is unsuccessful, a dissection should be considered. Large villous adenomas have a high potential for malignancy and must be completely removed.
Treatment of cancerous polyps depends on the depth of invasion of the mesenchymal epithelium into the polyp tip, the closest distance to the endoscopic resection boundary, and the degree of differentiation of the malignant tissue. If the malignant epithelium is confined to the mucosal muscle layer, if there is a clear resection line at the polyp tip or if the lesion is highly differentiated, endoscopic resection with close endoscopic follow-up should be sufficient. Infiltration through the mucosal muscle may invade the lymphatics and the likelihood of lymph node metastasis is increased. Partial colectomy should be performed for hypofractionated lesions or those with unclear resection boundaries at the polyp tip.
The timing of follow-up examinations after polypectomy is debated. Most authorities advocate a full colonoscopy (or barium enema if a full colonoscopy is not possible) twice a year and removal of newly discovered polyps. If no new polyps are found once a year for 2 consecutive years, subsequent colonoscopies are performed every 2 to 3 years.
Familial polyposis
A heterozygous autosomal dominant colon disease that can have 100 or more adenomatous polyps covering the colon and rectum.
A mutated dominant gene on the long arm of autosome 5 (FAP) is the causative factor. If left untreated, almost all patients will develop malignancy by the age of 40. Total proctocolectomy eliminates this risk, but because polyps in the rectum often degenerate after abdominal colectomy with ileorectal anastomosis, many authorities advocate performing this procedure first. The residual rectum needs to be examined every 3-6 m after subtotal colectomy; newly emerging polyps must be removed or electrocautery. If new polyps appear too quickly and on too many sides to be removed, the rectum needs to be removed and a permanent ileostomy performed. Follow-up and genetic counseling must be performed for patients and families with this disease.
Gardner syndrome is a variant of familial polyposis with sclerofibroma, cranial or mandibular osteoma, and sebaceous cysts. Other less common variants of familial polyposis include multiple colonic adenomas and other lesions.
Peutz-Jeghers syndrome is an autosomal dominant disorder in which multiple malformed polyps occur in the stomach, small intestine and colon. Symptoms include melanosis of the skin and mucous membranes, especially on the lips and gums.
Other polyps
Adolescent polyps are usually nonneoplastic, often grow faster than the blood supply, and dissociate themselves during puberty. Surgery is required only in cases of uncontrolled bleeding or intussusception. 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.
Colorectal cancer
Brief introduction
Colorectal cancer accounts for an increasing proportion of new cancers in Western countries each year, and is second only to lung cancer in incidence. 75,000 people died of colorectal cancer in the United States in 1989, of which approximately 70% were in the rectum and sigmoid colon, and 95% were adenocarcinomas. Colorectal cancer is the most common cause of death among malignant tumors that invade internal organs. Its incidence begins to rise at the age of 40 and reaches a peak at the age of 60-75. 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 to colorectal cancer is not obvious, but “cancer families” and “colon cancer families” (e.g., familial polyposis, Lynch syndrome) have been reported; in these families colorectal cancer can occur over several generations, often before age 40, and more often in the right hemicolectomy. In some cases of Lynch syndrome, there are mutations in at least four genes on autosomes 2, 3, and 7. Other susceptibility factors include chronic ulcerative colitis, granulomatous colitis, and familial polyposis (including Gardner syndrome); the risk of cancer at any given time with these diseases is related to the age of onset and the course of the underlying disease.
People with a high incidence of colorectal cancer consume diets containing less fiber and more animal protein, fat, and refined carbohydrates. Although carcinogens may be ingested through the diet, they are more likely to come from ingested food, bile or small intestinal secretions, through the action of bacteria. The exact mechanism of carcinogenesis is not known.
Colorectal cancer can spread through penetration of the intestinal wall by direct spread, hematogenous metastasis, local lymph node metastasis, perineural spread and intra-intestinal metastasis.
Symptoms, signs and diagnosis
Adenocarcinoma of the colon and rectum grows slowly and a relatively long period of time elapses before it reaches a large size that produces symptoms. Early diagnosis relies on routine examination. The development of symptoms depends on the location, type, extent and complications of the lesion. The right hemicolectomy is larger, has a thinner wall, and obstruction occurs late because of its fluid-like contents; the cancer often grows in a myxomatous pattern, the tumor may be so large that it can even be felt through the abdominal wall, occult bleeding often occurs, and fatigue and weakness due to severe anemia may be the only complaints. The lumen of the left hemicolectomy is small, the stool is semi-solid, and the cancer has a tendency to grow around the intestinal wall, thus causing alternating constipation and increased frequency of bowel movements or diarrhea. Partial and complete obstruction with abdominal cramps may be the main manifestation of the disease, and the stool may be in the form of thin strips or mixed with blood. The most common major symptom of rectal cancer is blood in the stool. When bleeding occurs in the rectum, even if accompanied by significant hemorrhoids or known diverticulosis, the possibility of concurrent cancer must still be ruled out. Rectal cancer may present with a feeling of urgency or incomplete defecation. There is no significant pain until the perirectal tissues are invaded.
A simple, inexpensive fecal occult blood test is desirable as part of a screening and surveillance protocol for high-risk individuals. To ensure accurate results, patients should consume a high-fiber, meat-free diet three days prior to stool sampling, and further testing is required in the event of a positive result.
Approximately 65% of colorectal cancers occur within the visualization of a curvable fiberoptic sigmoidoscope. Fiberoptic colonoscopy should be performed when cancer and colon related symptoms are suspected in any part of the intestine. If sigmoidoscopy reveals a lesion, a subsequent full colonoscopy should be performed and all lesions in the colon should be completely removed. Colonoscopic removal of concurrent polyps reduces the number of bowel segments to be removed. Endoscopic partial biopsy of polyps may have a 25% chance of misdiagnosis, and a negative biopsy does not completely rule out the possibility of cancer in the polyp. Surgical resection should be considered aggressively if the lesion is atelectasis or if it cannot be resected at colonoscopy.
Barium enema X-ray is not reliable for detecting rectal cancer, but it is a very important first step in diagnosing colon cancer. Air contrast X-ray may detect smaller lesions (<6 mm) than barium enema alone, but pneumatic colon may miss larger lesions (>2 cm) with an alarming rate (20% to 30%). The most important factor for barium enema and endoscopy of the colon is adequate bowel preparation, which often requires laxation, oral enterolaxatives and multiple enemas. In case of suspected obstructive colonic lesions, oral barium is prohibited because the colon absorbs the water in the barium suspension and may precipitate barium sulfate, thus producing complete colonic obstruction. Colonoscopy should be performed even when the x-ray diagnosis is fairly certain; barium enemas can cause 30% of tumors and 40% of polyps to be missed, whereas colonoscopy can detect coexisting lesions and determine the length of the resected bowel segment.
Elevated serum carcinoembryonic antigen (CEA) is not specifically associated with colorectal cancer, but CEA levels are elevated in 70% of patients. If CEA levels are elevated preoperatively and decreased after tumor resection, monitoring of CEA may help detect 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 extensive surgical resection of the colon cancer lesion and its local lymphatic drainage area after good bowel preparation. The choice of surgical approach for rectal cancer depends on the distance of the lesion from the anus and the extent of visualization. Ventral perineal resection of the rectum requires a permanent sigmoid colostomy. Low anterior resection with sigmoid-rectal anastomosis should be the treatment of choice only if it is possible to remove a normal segment of bowel 5 cm below the lesion and if this procedure is technically feasible. The use of a stapler (Stapler) then allows for a low anterior resection and anastomosis closer to the rectum in more patients without damaging their rectum.
Surgical procedures may result in cure in 70% of patients. The best 5-year survival rate can approach 90% if the cancer is confined to the mucosa, about 80% if the colon cancer has penetrated the lamina propria, and 30% if it has metastasized to the lymph nodes. Some colon cancers can be controlled locally by electrocoagulation if the patient cannot tolerate the risk of surgery. Preliminary findings suggest that supplemental radiation therapy after surgery for radical rectal cancer (but not colon cancer) can control local tumor growth, delay cancer recurrence, and improve survival in patients with limited lymph node involvement.
The use of preoperative radiation therapy to improve surgical resectability of rectal cancer is controversial; experts differ on whether this treatment increases the chance of operability or affects the detection of local lymph node metastases. Controlled studies of preoperative and postoperative chemotherapy combined with radiation therapy have been performed in patients with rectal cancer.
Appropriate controlled studies have found that the efficacy of 5-FU in combination with levamisole or folinic acid as adjuvant therapy for surgery in patients with colon cancer with positive lymph nodes (stage III, Dukes stage) has not been established.
There is debate about the length of follow-up after radical surgery for colorectal cancer. Most authorities advocate annual colonoscopy or X-ray examination of the residual bowel for 2 years, and subsequent re-examination every 2 to 3 years if the test is negative.
If radical surgery is not possible, limited palliative surgery may be required, with a median survival of 7 months. The only drug that has proven effective in advanced colorectal cancer is 5-FU, but only 15-20% of patients treated with this therapy have been shown to have tumor shrinkage and prolonged survival. The commonly used 5-FU regimen calls for 5 days of administration every 4-5 weeks, but should not be given if the physician is unfamiliar with the dangers of chemotherapy drugs and the nadir of blood counts. Although some oncologists believe that the combination of 5-FU with formyltetrahydrofolate is superior to 5-FU alone, other drugs, alone or in combination with 5-FU, have not usually been shown to have good efficacy. A new drug, irinotecan (camptosar), also has a role in progressive colon cancer patients when applied alone and has been evaluated as part of a combination chemotherapy regimen, but chemotherapy for patients with progressive colon cancer should be applied under the guidance of an experienced chemotherapist.
When metastases are confined to the liver, 5-FU or radioactive microspheres can be injected into the hepatic artery via an implanted subcutaneous pump or an external pump mounted on a belt, and the patient can walk around with the pump; this infusion therapy may be more effective than systemic chemotherapy, but these hepatic artery infusion therapy treatments are expensive and their value has yet to be proven in clinical studies. Hepatic arterial perfusion chemotherapy with a perfusion pump is not superior to systemic chemotherapy if metastases are also present outside the liver.
Anorectal cancer
The most common anorectal cancer is adenocarcinoma. Other tumors include squamous germinal cavity procarcinoma, melanoma, lymphoma, and various sarcomas. Epidermoid (non-keratinous squamous cell or basal cell) carcinoma of the anorectum accounts for 3% to 5% of distal colorectal cancers. Chronic fistulas, anal skin irradiation, mucosal leukoplakia, venereal lymphogranuloma, Bowen’s disease (carcinoma within the dermis) and acromegaly are its precancerous lesions and have been shown to be primarily associated with human papillomavirus infection. The tumors metastasize along the rectal lymph node ducts and inguinal lymph nodes. Basal cell carcinoma, Bowen’s disease (carcinoma within the dermis), extramammary Paget’s disease, germinal cavity procarcinoma, and malignant melanoma are less common.
The results of extensive local excision for perianal cancer are often satisfactory. The combination of chemotherapy and radiotherapy has a high cure rate for squamous and keratotic tumors of the anus. If radiotherapy and chemotherapy cannot reduce the tumor completely the abdominal perineum should be removed.
Pathogenesis of colorectal cancer
The incidence of colorectal cancer can occur in any part of the body from the cecum to the rectum, and the incidence rate of left hemicolectomy is higher in China, but there are reports that the incidence rate of right hemicolectomy is higher in women in high incidence areas. According to the statistical data of 3147 cases of colorectal cancer in China from the NCG, the left hemicolectomy below the splenic flexure and splenic flexure accounted for 82.0% of all colorectal cancers, among which the incidence of rectal cancer was the highest, accounting for 66.9%, which was significantly higher than that in Europe, America and Japan, where rectal cancer only accounted for 35%-48% of colorectal cancer. Colorectal cancers in other intestinal segments in order are sigmoid colon (10.8%), cecum (6.5%), ascending colon (5.4%), transverse colon (3.5%), descending colon (3.4%), hepatic flexure (2.7%), and splenic flexure (0.9%).
Bowel cancer can be divided into early stage cancer and progressive cancer according to the depth of tumor involvement. Early stage cancer is confined to the mucosa or submucosa of large intestine without lymph node metastasis.
1.General types
(1) Early stage cancer.
①Polyp augmentation type (Type I) can be further divided into tipped type (IP)), subtibial type (IS) or broad-based type, which is also mostly intra-mucosal carcinoma.
②Flat type: this type is mostly intra-mucosal carcinoma.
③Flat elevated type (IIa) is largely coin-shaped. This type mostly involves the submucosa.
④Flat elevated ulcer type (Ⅱa+Ⅱc) is roughly like a small disk with elevated edge and depressed center. This type involves the submucosa.
(2) Middle and late stage colorectal cancer: For a long time, the general typing of colorectal cancer is confusing. 1982, China Colorectal Cancer Pathology Research Collaborative Group made systematic and detailed observation on surgical specimens of surgically resected colorectal cancer and proposed to divide colorectal cancer into 4 types, which was adopted by National Anti-Cancer Association in 1991.
(1) Augmentation type: Any tumor whose main body protrudes into the intestinal lumen belongs to this type. The tumor may be nodular, polyp-like or cauliflower-like, with clear boundary, tipped or broad-based. The tumor is often clearly demarcated from the surrounding tissues and the infiltration is superficial and limited. If the tumor surface is necrotic and detached, ulcers can be formed.
Ulcerated type: It is the most common type. This type of tumor forms a deeper ulcer in the center, and the bottom of the ulcer reaches deeper or exceeds the muscle layer. According to the shape and growth of the ulcer, it can be divided into the following two types of subtypes.
A. Confined ulcer type: The ulcer has a crater-like appearance with a central necrotic depression, forming an irregular ulcer, and the edge of the ulcer is a berm-like tumor tissue that clearly rises above the intestinal mucosal surface.
B. Infiltrating ulcer type: This type of ulcer has the appearance of gastric ulcer. The tumor mainly thickens the intestinal wall by infiltrative growth, and then the central part of the tumor is necrotic and falls off to form a depressed ulcer, which is surrounded by tumor tissues covered with intestinal mucosa and slightly raised in a slope. If the ulcer is deeper, the local muscle layer may disappear completely.
(3) Infiltrative type: This type of tumor is characterized by infiltrative growth to all layers of intestinal wall. The intestinal wall at the lesion is thickened and the mucosal folds on the surface are thickened, irregular or disappeared and flattened. There is no ulcer in the early stage, but superficial ulcer may appear in the later stage.
Gum-like type: When a large amount of mucus is formed in the tumor tissue, the tumor section can be translucent and gelatinous, which is called gum-like type, and this type is seen in mucinous adenocarcinoma. The shape of gelatinous type varies, it may appear as a bulging mass, or it may form an ulcer or mainly infiltrate.
7 risk factors for colorectal cancer
In the 1970s, about 10 out of 100,000 people suffered from colorectal cancer, and the incidence rate has been increasing by 10% every year since then, and is higher in economically developed areas. Not to be ignored: the incidence of colorectal cancer is climbing!
Colorectal cancer and incidence site
The human intestine is divided into small intestine and large intestine, the latter including colon and rectum. The cancer tumors growing in the rectum and colon are collectively called colorectal cancer. Among them, cancer of the left hemithorax (rectum, sigmoid colon and descending colon) accounts for 75%, cancer of the right hemithorax (ascending colon) accounts for 20%, and cancer of the transverse colon accounts for only 5%. Rectal cancer has the highest incidence rate, accounting for about 60% of colorectal cancers.
Colorectal Cancer and Age of Onset
The incidence of colorectal cancer is mostly in people aged 41-60 years old (the first peak), followed by people under 40 years old (the second peak), and the incidence rate is lower in people over 61 years old (the third peak). The second peak of colorectal cancer is mostly concentrated in the age of 25~35, so young people should not 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 carcinogenic substances on the intestinal wall mucosa.
2, long-term loose stool caused by a variety of reasons, one of them is colorectal polyps, if polyps are not detected for a long time, they can collapse into cancer. The longer the time of loose stool, the greater the need for colonoscopy.
3.High protein and high fat diet, the metabolites of these foods in the body can easily induce cellular malignancy, which can lead to colorectal cancer.
4.Long-term inflammatory bowel disease ulcerative colitis is a kind of inflammatory bowel disease, and those who suffer from long-term improper treatment, relapse many times, and the course of the disease is more than 8 years should be alert to the occurrence of colorectal cancer.
5.Family history of colorectal cancer People of all ages with family history of this disease should pay attention to the emergence of colorectal cancer symptoms at all times.
About 80% of colorectal cancer comes from colorectal polyps, and patients with colorectal polyps must undergo regular colonoscopy.
Some patients with bleeding hemorrhoids have polyps or cancerous tumors in the large intestine above the anus, and if only bleeding symptoms are noted in the diagnosis, it is likely that important diseases in the large intestine will be missed! It is recommended that anyone with bleeding hemorrhoids must go to a hospital gastroenterology department for colonoscopy in the near future.
Clinical symptoms of colorectal cancer
When you find the following conditions, especially the first 6, you should go to the hospital early for further diagnosis and perform colonoscopy and other related examinations
(1) more frequent stools; (2) purulent or bloody stools; (3) multiple positive fecal occult blood; (4) after bleeding from hemorrhoids; (5) anemia; (6) abdominal pain; (7) abdominal distension; (8) loose stools or alternating loose and constipated stools; (9) inability to relieve stools; (10) abdominal mass; (11) decreased appetite; (12) wasting.
Differential diagnosis of colorectal tumors
(1) Hemorrhoids: Rectal cancer is often mistaken for hemorrhoids. Generally, internal hemorrhoids are painless bleeding with bright color and do not mix with stool, while blood in stool of intestinal cancer patients is often accompanied by mucus and rectal irritation symptoms.
(2) Amoebic enteritis: when the disease becomes chronic, granulation tissue proliferation at the base of the ulcer and surrounding fiber proliferation will thicken the intestinal wall and narrow the intestinal lumen, which can be easily misdiagnosed as cancer, and biopsy is required at this time.
(3) Intestinal tuberculosis: the age of onset is young, and there is a history of tuberculosis in other organs, and it usually occurs in the ileocecal region. However, proliferative intestinal tuberculosis, due to a large number of tuberculous granulomas and fibrous tissue proliferation, makes the intestinal wall thicken and harden, so it is easy to be confused with cecum cancer, and pathological biopsy is required to make a clear diagnosis.
(4) Restrictive enterocolitis: It is common in young people, with symptoms and signs such as abdominal pain, diarrhea, fever, wasting, anemia, loss of appetite, nausea, vomiting, abdominal mass and fistula formation, etc. It can be differentiated by x-ray barium meal and fiber colonoscopy.
(5) Chronic bacillary dysentery: patients can show abdominal pain, diarrhea, rarely pus and blood stool, mild urgency, the diagnosis is not difficult to make by stool culture, barium enema and endoscopy.
(6) ulcerative colitis: symptoms are similar to chronic bacillary dysentery, but there is a history of recurrent episodes, negative stool culture, sigmoid colon microscopy can be seen in the mucosa is fine granular changes, vascular texture disappeared, with erythematous congestion and small oval ulcers, its surface is often covered with yellowish-white exudate, serious cases have large irregular ulcers.
(7) Other differential diagnoses of colorectal tumors: such as phimosis lymphogranuloma, rectal endometriosis, colonic diverticulitis, etc., can be differentiated by symptoms, signs, x-ray examination and fiberoptic enteroscopy.
Post-operative colon cancer should pay attention to
After colorectal cancer surgery, colonoscopy should be performed according to the time specified by the doctor, because some colorectal cancer can occur in another part of the colon after surgery.
Types of colorectal tumors in the elderly
I. Papillary adenocarcinoma
All or most of the tumor tissue is papillary in structure. The papillae may be elongated or thicker and shorter, and their infiltration into the intestinal wall is often seen as papillae protruding into cystic glandular lumen of different sizes.
The papillae usually have less interstitial space. The epithelium covering the surface of the papilla is mostly single-layered, but it can also be multilayered, and the differentiation of cancer cells varies.
2. Ductal adenocarcinoma
It is the most common histological type of colorectal cancer, accounting for 66.9% to 82.1% of all colorectal cancers. Tubular adenocarcinoma is mainly characterized by the formation of glandular duct-like structure of cancer tissue. According to the degree of differentiation and heteromorphism of cancer cells and glandular duct structure, it can be further divided into 3 levels.
1.Highly differentiated adenocarcinoma: All or most of the cancer tissues are in the form of adenovascular structures. The epithelial cells are more maturely differentiated and are mostly lined with a single layer in the lumen of the glandular duct. The nucleus is mostly located at the base, and there is secretion in the cytoplasm, and there is cup-shaped cell differentiation.
2.Medium differentiated adenocarcinoma
Most of the adenocarcinoma tissue can still be seen in the form of glandular ducts, but the ducts are irregular in shape and vary in size and shape, or are branched; a small proportion of tumor cells are arranged in solid clusters or cords. Cancer cells are less differentiated: the anisotropy is more obvious.
The epithelium can be arranged into pseudo-layers, with uneven and overlapping nuclei, reaching the top of the cytoplasm, and reduced mucus secretion from the cytoplasm.
3.Lowly differentiated adenocarcinoma
This type of ductal adenocarcinoma is characterized by inconspicuous glandular duct structure, only a small part (1/3 or less) shows glandular duct structure, and the cell anomalies are more obvious.
4.Mucinous adenocarcinoma
This type of carcinoma is characterized by a large amount of mucus secreted by cancer cells and forms a “mucus lake”. In histology, two types of adenocarcinoma can be seen: one is an enlarged cystic glandular duct-like structure with a large mucus epithelium inside the capsule, and some epithelium is flattened or even disappears because the capsule is filled with mucus. The other type of histological manifestation is a large mucus lake with heaps of cancer cells floating in it, with poorly differentiated cells and large and deeply stained nuclei.
5.Indolent cell carcinoma
The tumor is composed of diffuse patches of ring cells and does not form glandular duct-like structure. When there is less mucus formation in the tumor cells, the nucleus may be round and the cytoplasm is pink stained without the characteristics of ring cells, but mucus staining can detect the mucus in the cytoplasm.
6.Undifferentiated carcinoma
The cancer cells grow diffusely in patches or in masses, without forming glandular ducts or other tissue structures. The cancer cells are usually small, with little cytoplasm and consistent size and shape, and sometimes they are not easily distinguished from lymphosarcoma.
7.Small cell carcinoma
It accounts for about 0.5%. The cancer cells are small in size and slightly larger than lymphocytes. The cancer cells are often arranged in close mosaic, with little cytoplasm, round, oval, melon or irregular nuclei, deeply stained nuclei and unclear nucleoli, and have higher malignancy.
8.Adenosquamous carcinoma
Adenocarcinoma is also called adenosquamous cell carcinoma, in which adenocarcinoma and squamous carcinoma are mixed. The adenocarcinoma part is generally well differentiated, with glandular structure or more cup-like cells and mucus secretion. In contrast, the squamous carcinoma component is generally less differentiated and has little keratinization.