Anal Cancer
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Introduction[edit | edit source]
it is one of the rare cancer, accounts for about 2% of all gastrointestinal tract malignancies. It is incidence increased by 2.7% annually in the last 10 years. It frequently faces considerable stigma, largely attributed to its connections with sexual practices and the sexual identities of individuals. The occurrence of anal cancer shows different patterns across Western countries. Statistics indicate that in the UK, Netherlands, Australia, and the USA, the frequency ranges from 0.7 to 1.7 cases annually per 100,000 individuals. In 2023 in the United States estimate around 1.96 million new cases of cancer in total, with anal cancer constituting approximately 0.5% of these cases, equating to about 9,760 instances. Additionally, out of an estimated 609,820 cancer-related deaths expected in the same year, around 0.3%, are anticipated to result from anal cancer[1].
In the majority of countries, women tend to have higher rates of incidence. In women under 40, anal cancer is rare, with its occurrence increase with aging[2] and those women who are over 65 are most affected, then the 50-64 age range, it is thought to be mainly linked to rising HPV infection rates[3].
Mechanism of Injury / Pathological Process[edit | edit source]
Squamous cell carcinoma (SCC) of the anal canal, often arising in the transformation zone between squamous and columnar epithelium, is characterized by a basement membrane that resembles those in skin adnexal and salivary gland neoplasms, lacking a myoepithelial layer. Predominantly, SCC displays squamous features, such as keratinization and intracellular bridges, in over 90% of cases. Nonkeratinizing cancer, identified above the dentate line, falls under the same category. Distinguishing SCC, especially from conditions like poorly differentiated adenocarcinoma or well-differentiated neuroendocrine carcinoma, involves detecting cytokeratin 5 and 6 (CK5 and CK6). The diagnostic process is further aided by immunohistochemical staining for p63 protein, located on chromosome 3's long arm, a frequent site for SCC genomic amplification. This categorization now includes basaloid, transitional, and spheroidal cancer variants under SCC.
Research on anal squamous cell carcinoma (ASCC) highlights frequent mutations in certain genes, especially in cases linked to HPV infection. These include genes in the PI3K/AKT/mTOR pathway, and genes like MLL2 and MLL3. HPV-negative ASCC cases often have mutations in tumor suppressor genes like TP53 and CDKN2A. There's a notable difference in the expression of the PD-L1 protein between HPV-positive and HPV-negative ASCC cases, which impacts patient survival rates. However, how these genetic factors affect treatment options for anal cancer is still under investigation.
Anal adenocarcinoma
Clinical Presentation[edit | edit source]
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Risk Factors[edit | edit source]
Diagnostic Procedures[edit | edit source]
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Outcome Measures[edit | edit source]
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Management / Interventions
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Differential Diagnosis
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Resources[edit | edit source]
References[edit | edit source]
- ↑ Islami F, Ferlay J, Lortet-Tieulent J, Bray F, Jemal A. International trends in anal cancer incidence rates. International journal of epidemiology. 2017 Jun 1;46(3):924-38.
- ↑ Kang YJ, Smith M, Canfell K. Anal cancer in high-income countries: increasing burden of disease. PLoS One. 2018 Oct 19;13(10):e0205105.
- ↑ Nelson RA, Levine AM, Bernstein L, Smith DD, Lai LL. Changing patterns of anal canal carcinoma in the United States. Journal of Clinical Oncology. 2013 Apr 4;31(12):1569.
