الفهرس 
PATHOLOGY OF COLORECTAL CARCINOMAOnly 14 pages are availabe for public view
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Abstract
colorectal cancer is one of the leading causes of death world wide. Unlike many other types of cancer, colorectal cancer can be prevented by removal of precancerous lesions. Thus, screening for such lesions is of utmost importance to prevent the incidence of malignancy. Also early detection and diagnosis of cancerous lesions in the long preclinical phase improves prognosis. Hence, the need for an accurate screening method for colorectal cancer has been established.
Potential screening options for colorectal cancer include fecal occult blood testing (FOBT), conventional colonoscopy, and double-contrast barium enema. Yet, virtual colonoscopy has many advantages over these. It is a fast non invasive procedure that requires no sedation. It can image the entire colon and localize lesions precisely, with sensitivity similar to that of colonoscopy when it comes to lesions >10 mm in diameter and superior to that of double contrast barium enema. It is safe, although there is a theoretical risk of radiation exposure. Virtual colonoscopy allows the detection of polyps located at the blind side of haustral folds, which can only be seen endoscopically with retro-flexion of the endoscope. The advent of multidetector-row scanning has been shown to improve accuracy of polyp detection by decreasing breathing artifacts.
At this point in time, the gold standard for colorectal cancer screening is still conventional endoscopic colonoscopy. Virtual colonoscopy can be and alternative to conventional colonoscopy in some conditions where patients are unwilling to undergo colonoscopy or where they are not fit for such invasive procedure. But so far, virtual colonoscopy has not yet been able to completely substitute for conventional colonoscopy in screening for colorectal cancer.
Virtual colonoscopy, now ten years old, has made substantial progress in the detection of adenomas and colorectal cancer thus acquiring the potential of becoming a credible tool for colorectal cancer screening. Additional studies need to be performed before routine application of virtual colonoscopy as a screening modality.
Several factors will likely converge in the very near future to precipitate wide-spread acceptance of CTC for colorectal screening
CT colonography (CTC), a complete examination of the colorectum using volumetric CT data combined with advanced imaging software, is gaining acceptance among radiologists and referring physicians. Over the past decade, numerous studies have reported technical improvements ,patient acceptance ,and performance evaluation for the detection of colorectal lesions and cancer
Computed tomographic colonoscopy CTC has evolved into a powerful technique for the detection of colorectal polyps in the last decade.
The advent of effective colorectal cancer screening with CTC allows a less invasive, accurate evaluation of the entire colon.
The excellent safety profile for CTC and very high completion rate compare favourably with optical colonoscopy, although optical colonoscopy is still considered the reference standard for detection of colorectal neoplasia.