Anal cancer

The anal cancer is a group of malignant neoplasms that can arise in the anal canal and anus margin perianal area.

The anal canal is the last portion of the large intestine , extending between 3 and 4 centimeters from the anorectal ring (region that separates the rectum from the anus) to the margin of the anus; said canal includes inside the so-called dentate or pectineal line , which is a transition zone between the glandular epithelium of the rectum and the squamous (lining) of the anus. Outside the margin of the anus, the squamous epithelium becomes the perianal skin.

Types of anal cancer

Given the different histology of these regions, there are different types of anal cancer ; thus, in the anal canal we can find:

• Squamous cell or epidermoid carcinoma . They are the most frequent, accounting for 55% of cases. They are found below the pectineal line .
• Basaloid or cloacogenic carcinoma. Located above the pectineal line . It constitutes 35% of the cases.
• Melanoma . It represents only 1% of the cases. It originates from the melanocytes located under the glandular epithelium.
• Adenocarcinoma . It’s very weird. It is more common in patients with chronic anal fistulas due to Crohn’s disease .

The following types may appear in the anus and perianal area :

• Squamous cell or epidermoid carcinoma. Also here it is the most frequent type, representing 70% of cases.
• Bowen’s disease . It is a squamous cell carcinoma in situ (localized).
• Adenocarcinomas . They are very rare also in the anus, being able to distinguish those that derive from the anal intermuscular glands, those that derive from the apocrine glands of the perianal skin and the perianal Paget’s disease.
• Other extremely rare malignant tumors in the anus in this area are lymphomas, muscle tumors, etc.

Anal Cancer Prognosis

The types with the best prognosis are squamous cell and basaloid carcinoma , while melanoma and adenocarcinoma have the worst course.

In general, anal cancer is very rare ; neoplasms of the anal canal are more common in women and middle ages, while those of the anus are more common in men and young patients .

The most frequent type, which, as we have already said, is the epidermoid, usually appears between the ages of 40 and 60 , with equal distribution of sex.

Causes of anal cancer (linea pectinea)

It is a disease of unknown cause.

There are some risk factors , such as perianal fissures , fistulas , condylomata acuminata , chronic hemorrhoids, and leukoplakia ; altogether, elements that suppose a chronic anal irritation.

There seems to be a greater risk in people who practice anal sex , due to the possible trauma that these may entail.

It is a neoplasm of unknown origin; from a given moment, the constituent cells of these tissues undergo a malignant transformation and proliferate uncontrollably, causing cancer; the risk factors previously exposed may or may not intervene in this process.

Throughout its evolution, cancer invades adjacent tissues and structures , such as the bladder, urethra, prostate, vagina, or pelvis. In addition, lymphatic dissemination of these tumors is frequent, the orientation of which will depend on the primary location.

Thus, neoplasms located above the pectineal line will spread upward, affecting the superior hemorrhoidal nodes; those located between the pectineal line and the margin of the anus , can spread upwards (to the superior hemorrhoidal nodes), laterally (to the iliac nodes), or downwards (to the inguinal nodes). This invasion will worsen the prognosis of the disease and add symptoms to the primary clinic.

Symptoms of anal cancer

The most frequent and common symptoms of the different types of anal cancer are:

• rectal bleeding
• perianal itching and pain
• alteration of bowel habit
• rectal tenesmus
• sensation of perianal mass
• ulceration

Some of the types have their own clinical characteristics; thus, in squamous cell carcinoma, fecal incontinence and anal discharge may also appear , melanoma may protrude outside the anus, and Bowen’s disease manifests as a single, hard, warty-looking lesion.

Diagnosis of cancer in the anus

As is usual in any disease, the first step will be to take a medical history , followed by the physical examination, which will focus on the anus and perianal region.

This examination, which will always include a rectal examination, must be very thorough, since it is common for the symptoms or lesions of these anal tumors to be attributed to other pathologies (such as hemorrhoids, fistulas or anal fissures), as they coincide; This means that, sometimes, the diagnosis of cancer is made at an advanced stage.

The physical examination will be complemented with a rectosigmoidoscopy , which will also allow taking a biopsy, which is necessary if the patient is to be treated with radiotherapy , either exclusively or preoperatively; However, this biopsy should not be performed if a local excision of the tumor (whose piece already allows the study of the lesion) is planned, due to the risk of carcinomatous implants. In any case, the definitive diagnosis is pathological .

Local extension and the presence of pelvic lymphadenopathy can be diagnosed by ultrasound and other tests.

The final studies will be aimed at discovering distant metastases.

It is very important, as we have already pointed out, and for the prognosis, that the diagnosis is made as early as possible. The ideal moment is, therefore, when the patient is still asymptomatic; Other signs of good prognosis are a reduced size of the lesion, its location on the anal margin, and that the tumor is keratinizing.

Anal cancer treatment

Treatment must be individualized, that is, it will vary greatly from one case to another, since it depends both on the histological type of the tumor and on its location and extension.

In general, in the case of tumors located in the anal canal , the treatment will be as follows:

• Squamous and basaloid carcinomas: if the diagnosis is made early and the tumor is small, it will be excised locally ; While if we are in more advanced stages, the combination of radio and chemotherapy (5-fluorouracil and mitomycin C) will be used first, followed by wide local excision of the residual tumor, or abdominoperineal amputation if it is extended.
• Melanoma : It seems that, unfortunately, the only effective treatment is abdominoperineal amputation .
• Adenocarcinoma : In general, an abdominoperineal amputation is usually necessary.

For tumors of the anus , in general, the treatments are:

• Squamous cell carcinoma : A wide local excision is performed; if there is lymph node involvement, this technique is accompanied by an inguinal lymphadenectomy . If there is extension to other structures, the abdominoperineal amputation will be performed. According to recent studies, there seems to be no difference between the results obtained with the use of radiotherapy and those of local excision.
• Bowen’s disease : It is treated with wide local excision .
• Adenocarcinomas : Abdominoperineal amputation is usually necessary.
• It should be noted that, in abdominoperineal amputation, the colostomy (which may also be necessary in other surgical techniques) is definitive.

Recent studies show that, with surgical treatments, survival at 5 years is 55-70% of cases, if there is no lymphatic involvement, while if there is, this survival is reduced to less than 20%.

According to these studies, the combined use of radio and chemotherapy achieves complete disappearance of the tumor in more than 80% of cases, if the initial lesion was smaller than 3 centimeters, with tumor recurrence occurring in less than 10%.

Thus, surgery could be reserved only for very extreme cases of tumor resistance or recurrence after medical treatment.

How can it be avoided?

Unfortunately, there is no effective prevention for this disease .

In any case, it is advisable to maintain strict medical control of any pathology that affects the anal and perianal regions, so that a diagnosis can be made as early as possible in the event of malignant transformation.

It is very important to consult a doctor before the appearance and persistence of the aforementioned symptoms, or of the pathologies listed as risk factors.