Perianal tumor

Introduction to perianal tumor Perianal tumors can easily invade the anal sphincter and cause symptoms, but early symptoms tend to be non-specific and can be easily ignored by patients and physicians, leading to delays in diagnosis. In the homosexual and bisexual population, the incidence of anal adenocarcinoma has increased significantly, especially in people infected with immunodeficiency virus (HIV). It has been found that the incidence of anal tumors is clearly related to the manner of sexual intercourse. basic knowledge The proportion of illness: 0.034% Susceptible people: homosexual and bisexual people Mode of infection: non-infectious Complications: anal fistula

The cause of perianal tumor

(1) Causes of the disease

Infection factor

HPV infection is associated with the occurrence of genital warts. HPV can have an incubation period of 40 years in the body, which can increase the incidence of squamous cell carcinoma. Squamous cell carcinoma is significantly associated with the history of genital warts. 26.9, female is 32.5), and transitional cell carcinoma has nothing to do with this. PCR detection of HPV-DNA (especially HPV-16) found that more than 80% of squamous cell anal duct tissues were positive, and anal epithelial cell carcinoma was The positive rate of male homosexual patients is also up to 80%. In female patients and male homosexual patients, HPV infection is more common in highly carcinogenic types (especially HPV-13 and HPV-16), and is mostly positive in anal canal cancer tissues. The reaction, while the skin cancer around the anus is rarely positive. It can be seen that anal canal cancer is just like cervical cancer. HPV is involved in the tumor, and HPV can be detected in the serum of 55% of anal canal cancer patients. -16 antibody, therefore HPV-16 antibody may be a tumor marker for anal canal cancer, in female patients without genital warts, anal cancer and herpes simplex type I (relative risk factor 4.1) and Chlamydia trachomatis (chlam Ydia trachomatis) (relative risk factor 2.3); in male patients without genital warts, it is associated with gonorrhea (relative risk factor 17.2).

In HIV-infected patients, the incidence of anal squamous intraepithelial lesions (ASIL) and squamous cell carcinoma is also high, and the relative risk factor for anal cancer after HIV infection is 84.1 in male homosexual patients. Non-homosexual patients were 37.8; the relative risk factor for anal cancer was 13.9 to 27.4 5 years before AIDS occurred. In addition, 20% to 45% of HIV-positive male patients had ASIL, while high anal squamous epithelium, internal damage Considered to be a precancerous lesion, recent studies have shown that HIV infection can contribute to HPV infection and promote the pathogenesis of HPV, whether in homosexual or bisexual patients. Statistics show that 93% of HIV-positive male patients HPV DNA can be detected in tissues in the anal area, compared with only 61% in HIV-negative cases. The above data indicate that HIV infection is beneficial for the replication of HPV with carcinogenic properties, and HIV can promote HPV-related diseases (such as ASIL and squamous cell carcinoma). ).

2. Smoking

According to reports, smoking has a synergistic effect on the pathogenesis of HPV, but there are also reports on the contrary. A recent study showed that perianal cancer occurs and smoking in premenopausal women and women with late menstruation. There is a significant correlation; there is no correlation between male and postmenopausal female patients, and it is speculated that the role of smoking in the pathogenesis of perianal cancer may be related to antiestrogenic effects.

3. The impact of related diseases

Studies have shown that some benign anorectal diseases are associated with the development of perianal cancer, such as anal fistula, anal fissure, perianal abscess and hernia. In the first year after the occurrence of these benign diseases, the relative risk factor of perianal cancer is high ( It was 12.0), followed by a significant decline. Others believe that these diseases may be complications of perianal cancer, but case-control studies have shown that this possibility is small.

In addition, there are reports in the literature that health search, inflammatory bowel disease and perianal cancer have a certain correlation with health search; immunosuppression after kidney transplantation can increase the chance of HPV infection by 100 times, so it can also increase the incidence of perianal cancer.

(two) pathogenesis

1. Biological characteristics

Squamous cell carcinoma originates from the anal canal epithelium. Since the anal canal epithelium originates from the embryonic ectoderm, squamous cell carcinoma exhibits more characteristics of skin adenocarcinoma, while rectal adenocarcinoma exhibits less performance and has a strong carcinogenic type. HPV (mainly HPV-13 and HPV-16) can integrate with the DNA of anal canal squamous cells, and therefore plays an important role in the development of anal canal cancer. Integration can be found in more than 80% of anal canal cancers. HPV-16.

At present, genetic predisposition has not been found, but gene abnormalities in the expression of p53 and c-myc can be detected in the development of anal canal cancer.

2. Type of histology

(1) Tissue type: squamous cell carcinoma (also known as epidermoid carcinoma) is the most common type of tissue, accounting for about 80% of perianal tumors. Most of the tumors around the anus are keratinized epithelium and well differentiated; Tumors in the anal canal are mostly non-keratinized epithelium and poorly differentiated. The tumors originating from the dentate line of the upper part of the anal canal are mostly mixed, and can have both adenocarcinoma and squamous cell carcinoma, also known as transitional cancer. , cloaca-derived or basal cell carcinoma, these three terms are actually the same concept, but basal cell carcinoma is currently the most commonly used.

Basal cell carcinoma accounts for 40% of anal epidermoid carcinoma, but this ratio may vary according to different evaluation criteria. From the perspective of clinical and prognosis, there is no correlation between the two types, so the treatment is basically the same. of.

In basal cell carcinoma, small cell carcinoma is highly malignant, and this type is similar to small cell lung cancer and is easily metastatic.

Anal adenocarcinoma is rare (generally reported in the literature is 5% to 10%, up to 18%), and the cases reported in the literature are gelatinous carcinomas derived from anal fistula and low rectal tumors.

(2) Precancerous state: In 80% of anal canal squamous cell carcinoma, severe dysplasia and carcinoma in situ are seen, especially squamous cell carcinoma derived from the perianal transitional zone is more common, anal squamous Intraepithelial lesions are another precancerous lesion; Bowen-like papulosis and Bowen's disease are common precancerous conditions.

(3) ICD-O classification: International classification of diseases for oncology (ICD-O) is shown in Table 1 (corresponding codes in parentheses).

3. Special types

Some rare subtypes of the perianal area include small cell carcinoma, lymphoma, malignant melanoma and leiomyosarcoma. Malignant melanoma accounts for 1% to 4% of perianal cancer, accounting for 1% to 2% of all malignant melanomas. Most of them only observe pigmentation under the microscope, and a few of them are visible to the naked eye. The anal malignant melanoma is easily confused with the thrombotic nucleus, which is easy to delay diagnosis.

4. Histological grading

The histopathological grade of perianal cancer is as follows:

G1: well differentiated;

G2: moderate differentiation;

G3: poorly differentiated;

G4: Undifferentiated.

Perianal tumor prevention

Patients with anal symptoms such as blood in the stool, perianal itching and discomfort should seek medical advice promptly, identify the cause, actively treat the primary anal disease, and avoid procrastination. For the perianal abscess that has already appeared, it is necessary to actively carry out anti-infective treatment. After the abscess is limited, abscess incision and drainage surgery should be performed to release the effusion.

Perianal tumor complications Complications

Anorectal abscess caused by Escherichia coli or anaerobic bacteria is easy to develop anal fistula. Once there is a hole with purulent secretion near the anus, it is necessary to be alert to the disease. For patients with low constitution and long-term use of immunosuppressive drugs, due to the poor anti-infective treatment effect, the infection is easy to spread, and even enter the blood circulation and bacteremia, high fever performance can occur, so clinical attention should be paid.

Perianal tumor symptoms Common symptoms Anal itching, blood and liver metastasis, inguinal lymph nodes, pus and bloody stools

First, the symptoms

1, the symptoms of perianal cancer are mostly non-specific, common blood in the stool, perianal itching and discomfort, symptoms often appear intermittently, it is not easy to cause patients to be alert, 70% to 80% of perianal cancer was initially diagnosed as benign disease, Bowen's disease is often accompanied by persistent itching of the anus. Paget's patients can be asymptomatic, but also can be expressed as perianal itching and hemorrhagic erythema. Perianal cancer is often associated with Paget's disease, leukoplakia, anal fissure, anal fistula, sputum and other diseases. Therefore, the diagnosis of perianal cancer is often difficult and misdiagnosed. Because of these reasons, early diagnosis is not possible, which makes the disease develop faster (60% to 70% of patients have a tumor diameter greater than 4 cm), and then gradually develop bowel pain. As well as changes in bowel habits, this suggests that lesion damage is often more pronounced, and anal incontinence or rectal-vaginal fistula may occur during the progression.

2, anal canal cancer is mostly anal canal infiltration ulcer, the edge of the ulcer is slightly harder; in the upper anal canal, the tumor can sometimes be polypoid, but the invasive changes can still be seen in the periphery.

3, the tumor that occurs in the lower anal canal often progresses quickly, the symptoms are obvious, the obvious mass is visible in the anus, or the mass is located in the back of the vagina, often involving the anus, the distal rectum and other adjacent tissues (such as the vagina, prostate, etc. ), in 15% to 20% of patients, the tumor may involve the pelvic rectal space, which may be manifested as perianal abscess or spasm.

4, perianal cancer can also be seen in inguinal lymphadenopathy, sometimes the first performance, the patient may not have any symptoms at this time, but inguinal lymphadenopathy is often misdiagnosed as inflammatory lymphadenopathy or hernia and delay the timely treatment of perianal cancer .

5. Individual cases have developed liver metastases when diagnosed as perianal cancer.

Second, clinical staging

Staging standard

(1) Determine the location

Perianal tumors mainly include two clinical types of anal canal tumors and tumors around the anal margin. However, the boundaries of these two sites and tumors are sometimes difficult to distinguish, so the current data may not be reported. Do the same.

According to the International Union Against Cancer/American Joint Committee on Cencer (IUAC/AJCC) standard, the anal marginal region refers to the hair-bearing skin and anal canal mucosa (according to the International Union Against Cancer/American Joint Committee on Cencer, IUAC/AJCC). The mucous membrane of the anal canal) or the connection of the slightly distal zone.

The anal canal refers to the area of the anorectal ring to the anal verge. The anus edge is deformed by the internal sphincter to make the mucous membrane toothy. It includes the transitional epithelium and the dentate line, but the anus The two sides of the marginal zone are not clearly defined, and the length of the anal transition is not exactly the same, either on the dentate line or under the dentate line.

(2) staging method

There are many methods for staging the anal canal cancer, but there is no uniform staging method. The clinical staging is mainly based on the depth of postoperative tumor infiltration; the ultrasound staging (proposed in 1991) is mainly based on ultrasound reconstruction images, and according to tumor size, Volume and perianal lymph node conditions determine the depth of invasion; the IUAC/AJCC standard considers tumors in the marginal region of the anus to be skin cancer.

(3) TNM staging of perianal skin cancer.

(4) Tumor staging of the anal marginal zone.

(5) TNM staging of anal canal cancer.

2. Judgment of clinical stage

(1) Basis of clinical staging

The correct clinical stage depends on reasonable and correct examinations. Anorectal digital examination and rectal examination are of great value in understanding the location and size of perianal tumors. The palpation of the surrounding tissues by the vagina is very infiltration to understand whether the lesions are infiltrated. It is helpful, especially for judging whether there is any invasion of the recto vaginal side and whether there is lymphadenopathy. If the patient feels pain during the examination, it can be considered under anesthesia; fine needle aspiration biopsy is also feasible for swollen inguinal lymph nodes. For highly suspected lesions, if the puncture results are negative, a surgical biopsy should be performed.

(2) Clinical stage of anal canal cancer

Endoscopic ultrasonography (EUS) can understand the depth of lesion invasion and surrounding lymph nodes. According to the surgical diagnosis, the depth of tumor invasion is often affected by the degree of tissue edema and inflammation, and there may be some errors. EUS is more accurate and measurable for judging the stage. The size of the lymph nodes, if the lymph nodes are larger than 1 cm, can be considered as a manifestation of metastasis. In addition, a fine needle aspiration biopsy can be performed on the enlarged lymph nodes.

Although EUS is mostly used for staging studies, in order to make the staging more accurate, it is sometimes necessary to rely on other tests, such as transvaginal ultrasonography, to determine whether the rectal vaginal wall is violated.

Abdominal and pelvic CT can help to understand whether the liver, pelvic organs, intraorbital lymph nodes, etc. have metastasis, MRI is more accurate than CT, in addition, chest X-ray examination is sometimes necessary.

(3) re-segmentation

After the treatment is completed, it is recommended to perform clinical and transanal endoscopic evaluation. This is of great value for understanding whether there is recurrence or the like. In the transanal endoscopic ultrasonography, the patient's tolerance is poor due to anal fibrosis. At this time, it is often difficult to distinguish between tumor recurrence and scar differentiation.

After radiotherapy, biopsy is not recommended, because perianal tumors tend to fade slowly (sometimes 2 months), and radiotherapy is also prone to radiation damage. If biopsy is performed, it may cause chronic anal fistula; for residual tissue after surgery, A careful clinical examination should be performed. If a recurrence is suspected, a multi-site biopsy may be considered. If the patient has significant pain, these tests should be performed under anesthesia.

Perianal tumor examination

1. The clinical significance of CEA test is very limited, the positive rate is not high, and the increase level is not directly related to tumor development and staging. It may be helpful for diagnosing liver metastasis and monitoring tumor recurrence. The expression of squamous cell carcinoma antigen is found in anal canal cancer. Higher sensitivity and specificity, but not related to tumor stage, limited clinical application, detection of HPV antigen, etc., its clinical value needs further study.

2, any suspicious lesions around the anal canal and anus should be biopsy, biopsy is also found in the inguinal suspicious lymph nodes, histological examination can also distinguish between anal canal squamous cell carcinoma and adenocarcinoma, for some patients with obvious pain, need to be anesthetized Lower needle biopsy is also feasible for swollen inguinal lymph nodes; for highly suspected lesions, if the puncture results are negative, a surgical biopsy should be performed.

3, using modern imaging methods such as liver B-ultrasound, CT and lung X-ray examination is easy to find whether there is liver, lung metastasis, but also more accurate.

Diagnosis and diagnosis of perianal tumor

Diagnostic criteria

The diagnosis of this disease depends on the anal canal, rectal examination and biopsy. Because of the superficial location of anal canal cancer, there are many early bleeding, pain and mass symptoms. Therefore, it is easier to find the lesion in the early stage of rectal examination. Anal examination can be performed. Understand whether there are perianal lesions, and make basic judgments on the location and size of the lesion. For any suspicious lesions in the perianal area, biopsy should be performed. The palpation of the surrounding tissue by the vagina is very helpful to understand whether the lesion is infiltrated. In particular, it is of great value in judging the presence or absence of invasion of the rectum and vagina.

In the anorectal examination, a circular stenosis can be found, and the patient may have obvious pain. Therefore, it can be performed under general anesthesia if necessary. The fingerprint can also determine whether there is metastasis of the lymph nodes around the rectum, and the lymph nodes of the inguinal region are easily accessible. However, its clinical significance is difficult to judge in the early stage. In perianal cancer, about one-third of patients may have inguinal lymphadenopathy, and 50% of lymph nodes may be found to be helpful for the diagnosis of tumor pathology.

Most patients have suffered from external hemorrhoids, anal fistula and perianal abscess. When these symptoms appear, they are often mistaken for the performance of the above-mentioned benign diseases, but they are not treated promptly, delay diagnosis, and the rate of misdiagnosis of iatrogenic is also high. 20%, the main reason is that when an anal canal cancer is seen, the rectal examination is not performed or because the physician lacks knowledge of anal canal cancer, the malignant tumor is misdiagnosed as a benign disease, and no histopathological examination is performed, so even Clinically, benign lesions should also be routinely biopsied to confirm the diagnosis. About half of the patients have been delayed from the primary symptoms to the diagnosis for 1 month, and about 1/4 of the patients have been delayed for 6 months. Therefore, nearly 50% The patient has become a progressive tumor (T3 to T4) when diagnosed as anal canal cancer.

Differential diagnosis

The disease should be identified with the following diseases:

Anal fistula

The disease manifests itself as a number of sickle-like creatures around the anal margin, which vary in size and can also extend into the lower end of the anal canal, but there is normal skin between the lesions, and there is no ulcer in the lesion.

2. Anal pruritus

The perianal skin of patients with chronic anal itching is extensively thickened, sometimes with small anal skin erosion, but the lesions are extensive but not erosive.

3. Non-specific ulcers

Can occur around the anus and affect the anal canal, the cause is unclear, the skin may have ulcers, but the lesion is superficial, the edge is slightly raised, biopsy can confirm that it is not a tumor.

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