الفهرس 
Anatomy of the Anal CanalOnly 14 pages are availabe for public view
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Abstract
SCC of the anal canal remains an uncommon disease. However, its incidence has been steadily increasing, reflecting a change in social mores and the attendant rise in sexually transmissible infections. HPV has been identified as the causative organism in most of these cancers, opening new avenues of research into the eradication of HPV-associated cancers.
Several histologic types of malignancy arise within the anus including squamous cell cancer (SCC) which is the most common, adeocarcinoma, melanoma and rarely sarcoma.
The majority of tumors arising in the transitional or squamous mucosa of the anal canal are squamous cell cancer ((the term anal cancer)) by common definitions refers to squmous cell cancers arising within the mucosa of the anal canal in contrast, adenocarcinoma arising from glandular elements within the anal canal are rare but appear to share a similar natural history of rectal adenocarciomas.
Balasoid feartures are identified in approximately 25 percent of squamous cell cancers of the anal canal and must be distinguished from basal cell carcinomas of the preianal skin which is classified as skin cancers. Balasoid (also termed junctional or cloacogenic) carcinoma is a variant of scc that arises from epithelial transitional zone ,theses terms have largely been abandoned because these tumors are now recognized as nonkeratinizing types of squamous cell carcinoma. tuomrs arising within the anal canal above the dentate line are termed nonkeratinizing sccs while those arising within the anal canal distal to the dentate line are termed keratinizing sccs.
Available imaging modalities are CT, MRI, endo-anal ultrasound (EUS) and positron emission tomography (PET) scanning.
Local staging should include magnetic resonance imaging (MRI) of the pelvis. Distant metastases, should be assessed with computerized tomography (CT) thorax and abdomen.
Together they allow assessment of the local extent including involvement of other structures, and spread to nodes and distant sites. As a minimum it is suggested patients undergo CT of chest, abdomen and pelvis as staging for metastatic disease.
MRI is currently the modality of choice to assess locoregional disease, but ultrasound can be useful for small lesions.
PET/CT with fluorodeoxyglucose (FDG-PET/CT) has been recommended in the current National Comprehensive Cancer Network treatment guidelines, because of high sensitivity in identifying involved lymph nodes, and high specificity in immunocompetent patients.
Surgical intervention for anal canal cancer remains a necessary option for select patients
The available data support the view that chemotherapy is necessary component of nonoperative therapy for anal cancer. Globally, combined modality therapy with RT and concurrent chemotherapy is considered the standard of care for squamous cell cancer of the anal canal. RT plus concurrent 5-FU plus mitomycin remains the standard regimen for concurrent chemoradiotherapy at most centers and in published guidelines of the NCCN
Sentinel node biopsy may ultimately direct the application of groin irradiation in patients with clinically and radiographically negative inguinal lymph nodes.
Local excision for small, superficial anal cancers maintains a controversial position in the treatment armamentarium, requiring further investigation.
Recurrent anal cancer poses a significant challenge, currently best managed with salvage APR or, for isolated regional disease, inguinal lymph node dissection. However, chemotherapy and other novel therapies are a focus for study for these recurrent and secondarily recurrent cancers.
The management of SCCs of the anal canal continues to evolve. So that squamous carcinoma of the anal canal is a disease which can be cured with radiation and chemotherapy while maintaining bowel function. The outcome however is related to disease stage at presentation. The local control and overall survival rates at 5 years of 60.7% and 65.6% respectively.
Cure can be achieved with widely available radiation techniques and chemotherapy agents. Early detection of this disease will improve the outcome for these patients.
The clinical course of squamous cell carcinoma of the anal margin is very different from that of the anal canal. The biology of anal margin cancer has not been actively explored and fully understood. There is a need to formulate a consensus approach for the clinical management of the disease. In addition, incorporation of new therapeutics in this disease especially in those with advanced stages should be explored.
The management of anal margin cancer has been evolving over the past three decades. The treatment paradigm has been shifted from radical surgical resection to an organ-preservation approach. Multimodality strategies incorporating radiation or even chemoradiation are frequently considered in some cases. However, because of the rarity of the disease, the disease frequently remains an overlooked topic