Prevalence of nonpolypoid colorectal neoplasia: an Italian multicenter observational study

Proportion of flat- and depressed-type and laterally spreading tumor among advanced colorectal neoplasia

BACKGROUND & AIMS

Flat- and depressed-type neoplasias along with laterally spreading tumors (LSTs) have been reported in colorectal neoplasias. We estimated the prevalence of flat and depressed types and LSTs along with their proportion among advanced neoplasias in a large average-risk population undergoing screening colonoscopy.

METHODS

This was a cross-sectional study performed at a single, general community institution, with subjects who were 40 to 79 years old, asymptomatic, and who had undergone their first colonoscopy for screening between 2003 and 2009 (n = 4910). Among the neoplasias detected, advanced neoplasias were morphologically classified as the polypoid type, flat and depressed type, or LST. We determined the prevalence and proportion for each type among the advanced neoplasias, with morphologies defined according to the Japanese endoscopic classification.

RESULTS

Advanced neoplasias were detected in 7.9% of men, 4.7% of women, and 6.1% of overall subjects. The polypoid type, the flat and depressed types, and the LSTs accounted for 75.3%, 7.5%, and 17.2% of advanced neoplasia, respectively. There was a high proportion of T1 cancers among the depressed types (40%). Approximately 80% of LSTs were located on the right side of the colon and more than 30% of LSTs showed high-grade dysplasia or T1 cancer.

CONCLUSIONS

Most advanced neoplasias detected were of the polypoid type. LSTs accounted for a considerable proportion among advanced neoplasia and tended to be located on the right side of the colon. The influences of any LSTs need to be taken into consideration for preventing colorectal cancer.

Preinvasive colorectal lesion transcriptomes correlate with endoscopic morphology (polypoid vs. nonpolypoid)

Improved colonoscopy is revealing precancerous lesions that were frequently missed in the past, and ∼30% of those detected today have nonpolypoid morphologies ranging from slightly raised to depressed. To characterize these lesions molecularly, we assessed transcription of 23,768 genes in 42 precancerous lesions (25 slightly elevated nonpolypoid and 17 pedunculated polypoid), each with corresponding samples of normal mucosa. Nonpolypoid versus polypoid morphology explained most gene expression variance among samples; histology, size, and degree of dysplasia were also linked to specific patterns. Expression changes in polypoid lesions frequently affected cell-cycling pathways, whereas cell-survival dysregulation predominated in nonpolypoid lesions. The latter also displayed fewer and less dramatic expression changes than polypoid lesions. Paradigmatic of this trend was progressive loss through the normal > nonpolypoid > polypoid > cancer sequence of TMIGD1 mRNA and protein. This finding, along with TMIGD1 protein expression patterns in tissues and cell lines, suggests that TMIGD1 might be associated with intestinal-cell differentiation. We conclude that molecular dysregulation in slightly elevated, nonpolypoid, precancerous colorectal lesions may be somewhat less severe than that observed in classic adenomatous polyps.

Risk factors and diagnosis of flat adenomas of the colon

In addition to histology, size and location, a morphologic description can be ascribed to polyps and adenomas. Traditionally, adenomas have been described as sessile and pedunculated, but it is now accepted that they can also present as flat or even depressed. Although first recognized in 1985, flat adenomas have become more common in Western published literature and in endoscopic reports. The Japanese Research Society Classification describes flat adenomas as lesions with a height that is less than one half of the diameter, while the Paris classification divides polyps into protruding and nonprotruding. The clinical significance of flat adenomas includes their potential malignancy, difficulty in detection and possible role in interval cancers. Serrated polyps represent a subset of polyps that have all the features that make flat lesions clinically important. Due to the relatively recent recognition of these lesions, as well as the technology required to detect them, the prevalence and malignant potential of these lesions in Western patients are still unknown. Finally, the best techniques and equipment for detecting flat polyps are also not established. In this article, we examine the issue of flat polyps and their significance in colorectal cancer screening with regard to prevalence, risk factors and methods for detecting flat polyps.