The term anal cancer comprises two groups of malignancies: carcinoma of the anal margin and carcinoma of the anal canal. A vast majority (approx. 90%) of all cancers developing in that region are a squamous cell carcinomas (and their numerous varieties). Adenocarcinoma (such as the most common colorectal cancer) is much less likely to develop in the anus. Some other malignant tumours may also occur in the anus.
Anal cancer does not occur frequently – approx. 220–280 new cases are diagnosed in Poland every year.
That cancer type is believed to develop due to the infection with human papilloma virus (HPV) which is also responsible for some neoplasms in the crotch region. Risk factors also include anal sex, history of cervical cancer (in women) and immunosuppressive therapy (e.g. following transplants).
Anal cancer has some early symptoms which should facilitate diagnosis. First of all, anal bleeding and palpable lump (hardening) occur in the skin next to the anus or in the short anal canal. The lump tends to have an uneven surface with ulceration. Such symptoms definitely require medical consultation and urgent diagnostic test with a specimen collected for microscopic analysis. Sometimes, the first symptom noticed by the patient is a lump in the groin – the inguinal lymph nodes are usually the first location where AC metastases occur. Therefore, if lumps in the groin appear, it is necessary – among other thins – to check the crotch region (anus, vulva, vagina, penis, etc.) for any cancerous changes.
It should be remembered that other non-malignant conditions, such as haemorrhoidal varix, anal fissura or anal abscess, may present with similar symptoms as early-stage AC. That similarity does not affect the need to exclude AC; to the contrary – it calls for a particularly careful differentiating diagnostics.
Treatment of choice for squamous cell carcinoma of the anal canal is radio- and chemotherapy (even with a high stage of the disease). Surgery is reserved for cases where the efficacy of conserving treatment is limited, or for relapsed disease.
In the case of squamous cell carcinoma of the anal margin, total resection of the tumour is recommended (if the tumour is not large and does not reach the sphincter). If it is of a larger size and/or if the sphincter is involved, conservative treatment is the first choice with concurrent radiotherapy. Should such treatment be ineffective or failed, surgery is resorted to. It consists in the total removal anus and rectum with a permanent abdominal colostomy (Miles’ abdominoperineal resection).
Adenocarcinoma of the anal canal requires the same procedure as rectal adenocarcinoma – typically, an extensive surgery is necessary involving the resection of the anus and rectum with a permanent abdominal colostomy. If metastases are found in the inguinal lymph nodes, removal of the inguinal lymphatic system is the procedure of choice (also known as inguinal lymphadenectomy).
General rules of follow-up after AC treatment are similar to those applied to other cancer patients.
In the first 2–3 years after treatment, follow-up visits should be held every 2–3 months, and for the next 2–3 years, every 4 months. Follow-up includes per rectum endoscopic anal assessment (e.g. rectoscopy, i.e. endoscopic inspection of the anal and rectal canal).
It should be stressed that a standard treatment using radiochemiotherapy causes the tumour to decrease very slowly; therefore, one should not jump to conclusions as to therapy failure or relapse. The attending doctor should be consulted in case of any doubts.