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Colorectal cancer is still one of the leading causes of
cancer-related death in the Western world. Screening colonoscopy is widely
accepted as the gold standard for early diagnosis of cancer. The prognosis
for patients with colonic neoplasms is strictly dependent on the depth of
infiltration, and therefore depends on early detection of preinvasive and
neoplastic changes. Early detection makes it possible to cure the patient by
immediate endoscopic resection.
In 2003, Sakashita et al. reported initial experience with real-time
confocal endoscopy in ex vivo specimens. The prototype endomicroscope
that was used (Olympus Optical Ltd., Tokyo, Japan) was passed through the
working channel of an endoscope. The aim of the study was to establish new
criteria for distinguishing between benign lesions and high-grade dysplasia
or cancer. The authors examined 100 endoscopically or surgically resected
colorectal lesions from 90 patients. Nuclei could not be visualized in
normal colonic mucosa or hyperplastic polyps, but were more often visible in
neoplastic lesions. Conversely, goblet cells were visible less often in
malignant or premalignant lesions. However, it should be noted that it was
not individual nuclei, but rather dark areas in irregular cells that were
visible. The study found a statistically significant difference between
nonneoplastic and neoplastic lesions in relation to the detection rate of
nuclei (dark areas) in laser-scanning confocal microscopy images.
On the basis of these results, the authors recommended preliminary criteria
for a confocal imaging classification of high-grade intraepithelial
neoplasia and cancer. Neoplasia was characterized by the presence of any
structural abnormality and clear visualization of nuclei. However, the
sensitivity of this method for predicting neoplasms in the colorectumwas
only 60%, reflecting the limited resolution of the system that was used.
In a recently published study (Kiesslich et al., Gastroenterology 2004) using the newly developed endomicroscopic
system, 42 patients with indications for screening or surveillance
colonoscopy after previous polypectomy underwent in vivo endomicroscopy with
the confocal laser endoscope. The aim of the study was to assess the
histology in vivo during ongoing colonoscopy in order to diagnose
intraepithelial neoplasias and colon cancer. Fluorescein-guided
endomicroscopy of intraepithelial neoplasias and colon cancers showed a
tubular, villous, or irregular architecture, with a reduced number of goblet
cells. In addition, neovascularization in neoplasms is characterized by an
irregular vessel architecture with fluorescein leakage. |
