Sun Xuejun  Lu Chunhua Xu Yongbo Han Gang Pan Longwen Chu Haibo
One-point anal protocarcinoma is a rare malignant tumor that occurs in the narrow ring area above the dentate line. It was first reported by Grinvslsky et al.  in 1956. There are not many literature reports at home and abroad, and the understanding of the disease is not unified. We have encountered 3 cases in the past 20 years, all of which were confirmed by surgery and pathology. The report is as follows and discussed in conjunction with literature.
1. clinical information
Example 1: The patient, a 51-year-old male, was admitted to the hospital on January 4, 2007 with a mass in his right abdomen due to habitual changes in stool for half a year. Six months ago, there was a change in bowel habits, sometimes blood in the stool, and symptoms worsened in the past two months, and there was an egg-sized mass in the right abdomen, which was active. Physical examination: the abdomen was flat and soft, and a 5cm×5cm mass was palpable at the Mc’s point on the right lower abdomen. Fiber enteroscopy: a huge irregular bulge at about 5cm from the anal margin for 2/4 weeks, superficial hyperemia, erosion, bleeding, hard texture, stenosis of the official cavity, ileocecal area for 2/3 weeks, ulcer type swelling Material, hard in nature. Admission diagnosis: multiple primary colorectal cancer: ① rectal cancer; ② ileocecal colon cancer. During the operation, the ileocecal tumor 5x5cm in size broke through the serosal layer, the mesangial lymph nodes were enlarged, and the rectal tumor was located below the presacral peritoneum reflex. Radical resection of the right colon, radical resection of rectal cancer and ligature colon-anal anastomosis were performed. The operation was smooth and the postoperative recovery was good. Pathological findings: tumors at the ileocecal junction, cancer cells were arranged in a tubular shape, with large and deep stained nuclei, obvious atypia, infiltrating serosal layer, and metastasis in 6/13 of mesangial lymph nodes. Rectal tumor cells are arranged in nests or beams, and the edges of cancer nests are arranged in fences. The cell atypia is obvious, nuclei are deeply stained, and mitoses are frequent. Squamous epithelial differentiation and necrosis can be seen. Pathological diagnosis: 1. Anal protocarcinoma at one point of the rectum 2. Moderately differentiated adenocarcinoma of the ileocecal area. Immunohistochemistry: NES (-), CK broad spectrum (++), CK high (+++), CK low (+), HMB45 (-), S-100 (-), immunohistochemistry support (rectal) One point anal carcinoma.
Example 2: Male, 58 years old, employee of this hospital. He was admitted to the hospital in April 1996 due to blood in the stool for more than 2 months. Digital rectal examination: a 2cmx2cm mass can be palpable at 12 o'clock in the thoracic and knee position and 5cm from the anal margin; fiber colonoscopy: the uplift accounts for 1/4 of a week, and the surface is congested, eroded, bleeding, and hard. Admission diagnosis: rectal cancer. Radical resection of rectal cancer was performed with colon-anal anastomosis, and the operation went smoothly. Pathological diagnosis: anal protocarcinoma at one point of rectum. The anus was painful and uncomfortable after the operation. After 2 months, he required surgery and was switched to miles surgery. Followed up for 11 years alive.
Example 3: A 42-year-old man was admitted to the hospital in October 1989 because of tenesmus and blood in the stool for more than 3 months.
Digital rectal examination: A 4cmx3cm mass and hard mass can be palpable at 7~12 o'clock in the thoracic and knee position and 3cm from the anal margin. Admission diagnosis: rectal cancer. Radical resection of rectal cancer was performed in situ anoplasty, the operation was smooth, and the pathological diagnosis: anal protocarcinoma at one point of the rectum. The ability to control bowel surgery is better, and the number of bowel movements after half a year is 2 to 3 times per day. Follow-up alive after 10 years.
The narrow annular area above the dentate line of the rectum is the remnant of the embryo's anus. There are columnar, squamous, transitional epithelium or three mixed epithelial tissues. The transitional epithelium in this area is cancerous and is called anal protocarcinoma, also known as cloaca. cancer. One-point anal protocarcinoma is a rare malignant tumor. The dentate line and its upper and lower adjacent areas are the most common sites. Klotz reported 373 cases of one-point anal protocarcinoma, located 44% below the dentate line. Line 38.9%, dentate line 13.3%. It is reported in the literature that its incidence accounts for 1% of anal canal cancer, and it is more common in women, with a high incidence of 40 to 60 years old . Domestic Wang Chengfeng  reported that its incidence accounted for 0.3% of anorectal cancer. It is very rare that a single-point anal protocarcinoma combined with colon cancer has not been reported in the domestic literature. The 3 cases in this group were all male, aged between 40 and 60 years old, and the tumor was located 1 to 3 cm on the dentate line.
The etiology of one-point anal carcinoma is unclear. Deans reported: its onset is related to smoking and sexual behavior, especially homosexual transanal sex is an important cause of the disease; human papilloma virus (type 16 virus) is caused by homosexuals. Sexual behavior is contagious and causes illness. There was no history of homosexuality in the three cases in this group. 2 cases smoked 10-20 cigarettes/day; case 2 did not smoke.
Marson divides it into three types according to the degree of cell differentiation: 1. Well-differentiated type: The cancer nest has a typical fence-like arrangement around the cancer nest and has a pseudo-adenoma structure. 2. Moderately differentiated type: the fence-like arrangement of cells around the cancer nest is not obvious, and there are more atypical cancer cells. 3. Undifferentiated type: diffuse cancer cells, lack of fence-like arrangement, obvious cell atypia, more frequent mitoses, and necrosis. I don’t know enough about its cytology in the past, so it is often named according to its shape, such as undifferentiated adenocarcinoma, basal cell carcinoma, basal cell carcinoma, transitional cell carcinoma, mucoepidermoid carcinoma, squamous adenocarcinoma, non-keratinized small cell squamous cell Cancer, etc., due to the in-depth research on it, confirmed that its source is the remnant of the anal anal embryo in the anal canal area-transitional epithelium .
The clinical manifestations are not specific. Hematochezia is the most common clinical symptom. Changes in bowel habits and rectal and anal discomfort are also more common. One-point anal protocarcinoma may be accompanied by perianal abscess, anal fistula, anal fissure, hemorrhoid hemorrhage and other complications, or a previous history of the above. Klotz et al. reported that more than 50% of cases had inguinal lymph node metastasis, as well as liver, lung, bone and other distant metastases. This disease is fashionable and needs to be differentiated from anal marginal epithelioid carcinoma, anal squamous cell carcinoma, and melanoma. Anal marginal epithelioid carcinoma is more likely to occur in the dentate line, most of which are younger than 60 years old, more common in men, mostly squamous cell carcinoma, less common in abdominal cavity Metastasis; anal squamous cell carcinoma has obvious epithelial cell changes, silver staining its epithelial base is incomplete; melanoma no matter whether there is melanin formation, S-100 tumor cells are all positive, which is one of the useful ways to distinguish this disease.
The disease needs to be confirmed by histological examination. Once the diagnosis is confirmed, radical treatment should be carried out as soon as possible, but there are still different opinions on which surgery and radiotherapy are the first choice. Because it originated in the transition zone and contains squamous cell carcinoma, it is more sensitive to radiotherapy. Feng Qiang  and others believe that: the treatment of primary anal carcinoma at one point should be surgery as the main supplement with a combination of radiotherapy and chemotherapy, but for patients with small primary lesions without peripheral invasion and good differentiation, tumors can also be used Local resection plus postoperative chemotherapy can also achieve better results. The prognosis of this disease is better than that of general rectal adenocarcinoma and squamous cell carcinoma. The 5-year survival rate of well-differentiated and moderately differentiated patients can reach 90%, and the undifferentiated patients have not reached 5 years. The prognosis of clinically advanced patients is poor. Wang Chengfeng  et al. The 1-, 3-, and 5-year survival rates were 83.3%, 33.3%, and 0%. Two patients in this group have survived for more than 10 years after operation.
1. Feng Qiang, Jie Shiguo, Liu Fusheng, et al. Analysis of the diagnosis and treatment of 12 cases of one-point anal protocarcinoma. Chinese Journal of Surgery 2003, 41 (11):877.
2. Wang Chengfeng, Shao Yongfu, Lan Zhongmin, et al. One-point anal protocarcinoma China Cancer and Rehabilitation 2000, 7(5): 56~57.
3. Kheir S, Hickey RC, Martin RG, et al. Cloacogenic Carcinoma of the anal canail. Arch Surg, 1972, 104:407~415.
4. Wu Jieping, Editor-in-Chief Qiu Fazu. Huang Jiasi Surgery 6th Edition Beijing: People's Medical Publishing House, 1025 ~ 1026.
 Author unit: General Surgery, 89th Hospital of PLA, Weifang, Shandong 261021