TAILIEUCHUNG - Chapter 087. Gastrointestinal Tract Cancer (Part 16)

Cancers of the Anus Cancers of the anus account for 1–2% of the malignant tumors of the large bowel. Most such lesions arise in the anal canal, the anatomic area extending from the anorectal ring to a zone approximately halfway between the pectinate (or dentate) line and the anal verge. Carcinomas arising proximal to the pectinate line (., in the transitional zone between the glandular mucosa of the rectum and the squamous epithelium of the distal anus) are known as basaloid, cuboidal, or cloacogenic tumors; about one-third of anal cancers have this histologic pattern. Malignancies arising distal to the. | Chapter 087. Gastrointestinal Tract Cancer Part 16 Cancers of the Anus Cancers of the anus account for 1-2 of the malignant tumors of the large bowel. Most such lesions arise in the anal canal the anatomic area extending from the anorectal ring to a zone approximately halfway between the pectinate or dentate line and the anal verge. Carcinomas arising proximal to the pectinate line . in the transitional zone between the glandular mucosa of the rectum and the squamous epithelium of the distal anus are known as basaloid cuboidal or cloacogenic tumors about one-third of anal cancers have this histologic pattern. Malignancies arising distal to the pectinate line have squamous histology ulcerate more frequently and constitute 55 of anal cancers. The prognosis for patients with basaloid and squamous cell cancers of the anus is identical when corrected for tumor size and the presence or absence of nodal spread. The development of anal cancer is associated with infection by human papillomavirus the same organism etiologically linked to cervical cancer. The virus is sexually transmitted. The infection may lead to anal warts condyloma accuminata which may progress to anal intraepithelial neoplasia and on to squamous cell carcinoma. The risk for anal cancer is increased among homosexual males presumably related to anal intercourse. Anal cancer risk is increased in both men and women with AIDS possibly because their immunosuppressed state permits more severe papillomavirus infection. Anal cancers occur most commonly in middle-aged persons and are more frequent in women than men. At diagnosis patients may experience bleeding pain sensation of a perianal mass and pruritus. Radical surgery abdominal-perineal resection with lymph node sampling and a permanent colostomy was once the treatment of choice for this tumor type. The 5-year survival rate after such a procedure was 55-70 in the absence of spread to regional lymph nodes and 20 if nodal involvement was present. An .

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