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Clinicopathologic Characteristics and Malignant Potential of Colorectal Flat Neoplasia Compared with that of Polypoid Neoplasia

  • Original Contributions
  • Published:
Diseases of the Colon & Rectum

Abstract

Purpose

Because of their potential for malignancy, flat colorectal neoplasias are a current topic of debate. This study was designed to investigate the clinicopathologic features of flat neoplasia and to compare them with those of polypoid neoplasia, as well as to identify the determinants of malignant transformation of both flat and polypoid colorectal neoplasia.

Methods

A prospective, cross-sectional study of 3,360 patients diagnosed with adenomas via total colonoscopy and polypectomy was performed at 11 tertiary medical centers between July 2003 and July 2004. In this study, potential risk factors for malignant transformation were analyzed. If multiple adenomas were identified, then only the adenoma with the most advanced degree of histology was recorded for the patient.

Results

Of a total of 3,360 neoplasias identified, we found that the incidence of flat and polypoid neoplasias were 207 (6.2 percent) and 3,153 (93.8 percent), respectively. Patients with flat neoplasias tended to be older (59.6 vs. 57.1, P < 0.01), with the neoplaisa located more frequently in the right colon than polypoid neoplasias (49.3 percent vs. 32 percent, P < 0.01). The incidence of high-grade dysplasia or cancer in flat neoplasias was similar to that of polypoid neoplasias (5.4 percent vs. 4.6 percent, P = 0.36). Multivariate analysis revealed that a size of ≥11 mm (odds ratio, 6.8; 95 percent confidence interval, 4.8–9.7) and location in the left colon (odds ratio, 1.6; 95 percent confidence interval, 1.1–2.4) were significant determinants for the malignancy potential of colonic neoplasias.

Conclusions

The clinicopathologic indices for the propensity of malignant transformation in colorectal neoplasias were a size ≥11 mm and location in the left colon rather than flat gross morphology.

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Acknowledgments

The authors thank the pathologists at each of the 11 participating hospitals: Hogeun Kim, M.D., Mi Yun Cho, M.D., Youn Wha Kim, M.D., Se Jin Jang, M.D., Kye Won Kwon, M.D., Mee-Hye Oh, M.D., Yang Seok Chae, M.D., and Kyoung Mee Kim, M.D., who made a significant contribution to the performance and successful completion of the study.

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Authors and Affiliations

  1. Department of Internal Medicine and Institute of Lifelong Health, Yonsei University, Wonju College of Medicine, 162 Ilsan-dong, Wonju, 220-701, South Korea

    Dong Hun Park M.D. & Hyun Soo Kim M.D.

  2. Yonsei University College of Medicine, Seoul, South Korea

    Won Ho Kim M.D. & Tae Il Kim M.D.

  3. Sungkyunkwan University College of Medicine, Seoul, South Korea

    Young Ho Kim M.D. & Dong Il Park M.D.

  4. Kyunghee University College of Medicine, Seoul, South Korea

    Hyo Jong Kim M.D.

  5. Ulsan Yonsei University College of Medicine, Seoul, South Korea

    Suk-Kyun Yang M.D. & Jeong-Sik Byeon M.D.

  6. Soonchonhyang University College of Medicine, Buchon and Chonan, South Korea

    Moon Sung Lee M.D. & Il Kwun Chung M.D.

  7. Ewha Woman’s University College of Medicine, Seoul, South Korea

    Sung Ae Jung M.D.

  8. Korea University College of Medicine, Seoul and Ansan, South Korea

    Yoon Tae Jeen M.D. & Jai Hyun Choi M.D.

  9. Catholic University College of Medicine, Inchon, South Korea

    Hwang Choi M.D.

  10. Hanyang University College of Medicine, Kuri, South Korea

    Dong Soo Han M.D.

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  1. Dong Hun Park M.D.
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  2. Hyun Soo Kim M.D.
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  3. Won Ho Kim M.D.
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  4. Tae Il Kim M.D.
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  5. Young Ho Kim M.D.
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  6. Dong Il Park M.D.
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  7. Hyo Jong Kim M.D.
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  8. Suk-Kyun Yang M.D.
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  9. Jeong-Sik Byeon M.D.
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  10. Moon Sung Lee M.D.
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  11. Il Kwun Chung M.D.
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  12. Sung Ae Jung M.D.
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  13. Yoon Tae Jeen M.D.
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  16. Dong Soo Han M.D.
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Corresponding author

Correspondence to Hyun Soo Kim M.D..

Additional information

Invited Commentary

In this article by Park et al., the data of a multicenter study on the malignant potential of flat neoplastic lesions in the colon and rectum are reported. Most of the previous studies from Japan and some from Western countries show that flat lesions have higher malignancy rates than polypoid lesions. However, some recent reports and the one under discussion present data showing that the rate of malignant transformation is not related to the flat gross morphology.

There are two possible explanations for the discrepancy in the rate of malignant transformation of flat lesions between the present report and previous ones (mainly by Japanese authors). First, according to the Japanese reports, it is clear that the “flat and depressed” lesions have a higher malignancy rate than the polypoid lesions. It is noteworthy that the rate of malignant change in flat and depressed lesions has been reported to be higher while such lesions are still small. In the present study, flat and depressed lesions were excluded from their analysis because the number of flat and depressed lesions was very small (only 3). The small number of flat and depressed lesions might be because of the multicenter nature of the study in which 40 colonoscopists from 11 institutes were involved. The authors stated that, in their study, there were no guidelines regarding the use of instruments, such as the chromoscopy. Therefore, their colonoscopy methods might not have been sufficient to detect flat and depressed lesions under colonoscopic observation. The small number of flat and depressed lesions and the exclusion of such lesions from the analysis in the current study is the point that is obviously different from most of the Japanese studies. This point was mentioned by the authors in their discussion.

The second difference is that, in the present study, “laterally spreading tumors” (LSTs) were recorded as flat neoplasia if they had a diameter several times greater than the height. As the authors stated, “granular-type LSTs” were categorized as flat lesions in the study. Kudo et al. proposed the concept of LSTs, including both granular and nongranular tumors. Although the latter is classified as a type of flat lesion, the former corresponds to the so-called large sessile adenoma or villous papilloma. The height (or thickness) of granular LSTs often is more than twice that of normal mucosa. Histologically, granular LSTs often show a growth pattern similar to that of polypoid adenomas. Therefore, a significant number of granular LSTs were not classified as flat lesions in most of the Japanese reports. Although it often has been reported that the malignancy rate of large sessile adenomas (granular LSTs) is higher, the size of these lesions often is greater than that of the usual polypoid lesions. And the malignancy rates by size are not at all higher than those of polypoid lesions.

Considering the above-mentioned two differences in the inclusion criteria for flat lesions between the current report and most of the previous Japanese reports, the results of the present study by Park et al. are understandable, but the data should be interpreted carefully. It is important for the readers to recognize the differences in the materials used and in the definitions given to “flat lesions” when reading reports on the malignant transformation rate of flat neoplastic lesions in the large bowel.

Fumio Konishi, M.D.

Saitama City, Japan

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Park, D.H., Kim, H.S., Kim, W.H. et al. Clinicopathologic Characteristics and Malignant Potential of Colorectal Flat Neoplasia Compared with that of Polypoid Neoplasia. Dis Colon Rectum 51, 43–49 (2008). https://doi.org/10.1007/s10350-007-9091-5

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  • DOI: https://doi.org/10.1007/s10350-007-9091-5

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