Small flat cancer of the rectum: clinicopathologic and endoscopic features

Methylation epigenotypes and genetic features in colorectal laterally spreading tumors

Aberrant DNA methylation plays an important role in genesis of colorectal cancer (CRC). Previously, we identified Group 1 and Group 2 methylation markers through genome-wide DNA methylation analysis, and classified CRC and protruded adenoma into three distinct clusters: high-, intermediate- and low-methylation epigenotypes. High-methylation epigenotype strongly correlated with BRAF mutations and these aberrations were involved in the serrated pathway, whereas intermediate-methylation epigenotype strongly correlated with KRAS mutations. Here, we investigated laterally spreading tumors (LSTs), which are flat, early CRC lesions, through quantitative methylation analysis of six Group 1 and 14 Group 2 methylation markers using pyrosequencing. Gene mutations in BRAF, KRAS and PIK3CA, and immunostaining of TP53 and CTNNB1 as well as other clinicopathological factors were also evaluated. By hierarchical clustering using methylation information, LSTs were classified into two subtypes; intermediate-methylation epigenotype correlating with KRAS mutations (p = 9 × 10(-4)) and a granular morphology (LST-G) (p = 1 × 10(-7)), and low-methylation epigenotype correlating with CTNNB1 activation (p = 0.002) and a nongranular morphology (LST-NG) (p = 1 × 10(-7)). Group 1 marker methylation and BRAF mutations were barely detected, suggesting that high-methylation epigenotype was unlikely to be involved in LST development. TP53 mutations correlated significantly with malignant transformation, regardless of epigenotype or morphology type. Together, this may suggest that two molecular pathways, intermediate methylation associated with KRAS mutations and LST-G morphology, and low methylation associated with CTNNB1 activation and LST-NG morphology, might be involved in LST development, and that involvement of TP53 mutations could be important in both subtypes in the development from adenoma to cancer.

Comparison of the clinicopathologic features between flat and polypoid adenoma

OBJECTIVE

Several reports have suggested that flat colorectal adenomas might exhibit a higher potential for malignancy compared to polypoid adenomas. Although the clinical importance of the shape of polyps is stressed, the controversy surrounding the malignant potential of flat adenomas continues. The aim of this study was to compare the clinicopathologic characteristics, including degree of dysplasia and malignancy, between flat and polypoid adenomas 5 mm in size or larger.

MATERIAL AND METHODS

A total of 3263 polyps (254 flat adenomas and 3009 polypoid adenomas), >/=5 mm in size, diagnosed in 1883 patients by colonoscopy were analyzed.

RESULTS

Flat adenomas were found in 10% of patients, which represented 7.8% of all adenomas removed. The flat adenomas were larger in diameter than the polypoid adenomas (14.8+/-12.6 mm versus 8.6+/-5.0 mm, p <0.01), had a higher rate of villous components (18.5% versus 11.4%, p <0.01), a higher rate of high-grade dysplasia (9.4% versus 4.2%, p <0.01), and a higher rate of malignancy (10.2% versus 3.6%, p <0.01) than polypoid adenomas. However, there was no difference in the rate of high-grade dysplasia or carcinoma between flat and polypoid adenomas of equal size. It was shown by multivariate analysis that rectosigmoid location, larger size, and presence of a villous component were associated with a higher rate of malignancy, but not with flat morphology.

CONCLUSIONS

Flat adenomas, which were of a relatively large size in this study, were not associated with a higher risk for high-grade dysplasia and carcinoma compared with polypoid adenomas.

Flat adenomas

This article was presented at the conjoint CSSA and RACS (colorectal section) spring meeting Queensland, Australia, September 2004. The adenoma-carcinoma sequence describes a succession of events from polypoid adenoma to colorectal cancer. However, this model only accounts for up to two-thirds of colorectal cancers. There is growing evidence that flat adenomas are precursor lesions to a flat type of colorectal cancer and certain subtypes of these polyps are at greater risk of malignant transformation. If confirmed, the implications for screening, endoscopic recognition and management will become of increasing importance if we are to decrease the incidence of colorectal cancer.

Clinicopathologic and immunohistochemical study of small apparently "de novo" colorectal adenocarcinomas

Rarely, adenocarcinomas of the colorectum develop as small (< or =1.0 cm) rapidly invasive tumors without an obvious adenomatous or "in situ" component. These tumors have been termed "de novo" carcinomas. Although it is believed by some that these tumors are more aggressive than conventional large adenocarcinomas with an identifiable in situ component, little is known about the biologic characteristics and natural history of these lesions. The aim of this study was to evaluate and compare the pathologic features, biologic characteristics, and natural history of small apparently de novo invasive colorectal adenocarcinomas with conventional large (>1.0 cm) carcinomas. Routinely processed specimens from 20 patients (M/F ratio: 13/7; mean age: 65 y) with small apparently de novo invasive colorectal adenocarcinomas (all < or =1.0 cm in size) were evaluated for a variety of clinical and pathologic features. In addition, immunostains for p53, beta-catenin, DPC4, hMLH1, hMSH2, and MGMT were evaluated in all cases. The findings in this group of cases were compared with those from 20 control patients (M/F ratio: 8/12; mean age: 60 y) with stage-matched conventional "large" colorectal adenocarcinomas (all >1.0 cm in size). Patients were followed for a mean of 52.6 and 60.6 months, respectively, for the 2 groups. Small apparently de novo invasive adenocarcinomas were present in the left colon, transverse colon, and right colon in 85%, 10%, and 5% of cases, respectively. Their mean size was 7 mm (range: 3 to 10 mm). All cases were stage T1 and the majority were moderately differentiated (75%). Only 1 (5%) patient had lymph node metastases. Two (10%) cases were mucinous and only 1 (5%) showed prominent tumor infiltrating lymphocytes. Upon complete sectioning of the tissue blocks of tumor, residual foci of adenomatous epithelium were present in 16/20 (80%) cases, of which 75% contained foci of high-grade dysplasia. P53 and nuclear beta-catenin staining was present in 70% and 85% of cases, respectively, but only 5 cases (25%) showed loss of DPC4. Loss of MGMT expression was seen in 5 cases (25%), loss of hMSH2 in only 1 case (5%), and none showed loss of hMLH1. Only 2 patients (10%) developed visceral metastases upon follow-up. Control patients had similar demographic features, clinical outcome, anatomic distribution of tumors, degree of differentiation, and prevalence of positivity for the immunostains noted above, to the study cases. In our patient population, true small de novo colorectal adenocarcinomas, tumors that lack an identifiable adenomatous component, are exceedingly rare, because complete tissue sectioning reveals residual adenomatous tissue in the majority of cases. The biologic characteristics and natural history of small carcinomas with a minimal dysplastic component, and those with no identifiable adenomatous component, are similar to conventional large (>1 cm) adenocarcinomas, and, thus, they should probably be treated similarly.

Recent advances in chromoscopic colonoscopy and endomicroscopy

The basic rationale for secondary prevention of colorectal carcinoma is by endoscopic polypectomy. New technologies in the form of high-magnification or "zoom" colonoscopy complemented by chromoscopic agents permit early detection of neoplastic colorectal lesions, particularly flat and depressed types. Detailed morphologic characteristics of the surface crypt or "pit pattern" can be obtained with these techniques, enabling an in vivo "optical biopsy" and staging tool. Establishing suitability for endoscopic resection or surgical excision can be enhanced using these techniques. Furthermore, chromoscopic colonoscopy may have a role in routine endoscopic colorectal cancer surveillance programs in patients at high risk for colorectal neoplasia, such as those with long-standing ulcerative colitis and familial colorectal cancer syndromes. This review summarizes recent data regarding the prevalence and histopathologic characteristics of flat and depressed colorectal lesions in Western cohorts and describes how their detection and management can be improved by chromoscopy and magnification technology. We outline these techniques from a clinical perspective and describe the basic principles of endoscopic mucosal resection.

A novel retrograde-viewing auxiliary imaging device (Third Eye Retroscope) improves the detection of simulated polyps in anatomic models of the colon

BACKGROUND

Colonoscopy is the "gold standard" for colorectal polyp and cancer detection, but important lesions may be missed on the proximal aspect of haustral folds, rectal valves, or flexures.

OBJECTIVE

Our purpose was to evaluate a prototype auxiliary imaging device that extends beyond the colonoscope's tip, providing a continuous retrograde view to detect lesions missed by the forward-viewing colonoscope.

DESIGN

Three anatomic models of the colon were prepared with simulated polyps, 32% in obvious locations and 68% on the proximal aspect of folds. Six endoscopists examined each model with two methods. Method A used a standard video colonoscope. Method B involved an identical colonoscope with a retrograde-viewing auxiliary device positioned within its instrument channel. Order of testing was randomized and blinded.

SETTING

Laboratory bench.

MAIN OUTCOME MEASUREMENTS

Detection rates for simulated polyps.

RESULTS

Of 78 "obvious" polyps, 69 (88%) and 70 (90%) were detected by methods A and B, respectively (P > .9). In contrast, of 162 polyps on proximal aspects of folds, 20 (12%) and 131 (81%) were detected by methods A and B, respectively (P < .00001).

LIMITATIONS

Limitations resulted from (1) use of commercially available anatomic models in which haustral folds are less prominent and more rigid than in humans and (2) evaluation of a prototype device that had larger size and narrower angle of view than the planned production model and that was fixed in relation to the colonoscope.

CONCLUSIONS

In simulated testing, a retrograde-viewing auxiliary imaging device used with a standard video colonoscope significantly improves detection rates of simulated polyps and promises to enhance the diagnostic yield of colonoscopy in humans.

Practical uses of chromoendoscopy and magnification at colonoscopy

New technologies in the form of high-magnification or zoom colonoscopy complemented by chromoscopic agents permits early detection of neoplastic colorectal lesions, particularly flat and depressed types. Establishing suitability for endoscopic resection or surgical excision can be enhanced using these techniques. Chromoscopic colonoscopy may play an important role in the routine endoscopic colorectal cancer surveillance programs in patients assuming a high risk of colorectal neoplasia. This article summarizes recent data regarding the prevalence and histopathologic characteristics of flat and depressed colorectal lesion in Western cohorts and describes how their detection and management can be improved by chromoscopy and magnification technology. The techniques required for chromoscopic colonoscopy and magnification imaging are outlined along with a review of the literature on these subjects.

Microsatellite analysis of sporadic flat and depressed lesions of the colon

Prior studies of molecular and genetic derangements in flat and depressed lesions of the colon have revealed lower frequencies in a number of markers commonly present in exophytic lesions. These and other differences suggest that flat lesions are driven by alternative pathways. We reviewed a database of patients who had undergone endoscopic mucosal resection (EMR) for flat and depressed lesions at the University of Chicago from January 2001 to April 2003. Formalin-fixed and paraffin-embedded colonic samples were retrieved from the tissue bank, and five standardized mononucleotide and dinucleotide microsatellite regions were analyzed for instability (MSI) using fluorescently labeled forward primers in nonmultiplex reactions. Sixteen patients were identified with flat or depressed lesions who had adequate tissue specimens available for MSI analysis. Of these specimens, eight were tubular adenomas, three were tubulovillous adenomas, and five were carcinomas in situ. Four of the lesions were microsatellite unstable, each at a single locus, and one lesion showed probable instability at a second locus. Eleven lesions were microsatellite stable. Aberrations in DNA repair mechanisms do not appear to significantly contribute to the molecular derangements underlying sporadic flat or depressed colonic lesions. The molecular bases that underlie the aggressive behavior of sporadic flat and depressed lesions remain to be determined, and further investigation is warranted.

Flat Colorectal Lesions: Colonoscopic Detection Without Dye Spray or Magnification and Clinical Significance

OBJECTIVE

The detection of flat colorectal lesions with possible malignant potential has been described by Japanese endoscopists. This study looks at the detection of flat lesions using standard colonoscopic techniques and examines the clinical significance of these lesions.

METHODS

The records of patients who underwent complete colonoscopy by a single colorectal surgeon in an outpatient setting over a 4-year period were reviewed. The site and number of flat lesions and their histology were noted. Patients with incomplete intubation of the colon were excluded.

RESULTS

A total of 491 patients underwent 593 colonoscopic examinations. There were 236 flat lesions identified in 91 patients: 24% (56/236) were adenomas showing mild or moderate dysplasia, and 63% (148/236) were hyperplastic.

CONCLUSIONS

Flat colorectal lesions are common and can be detected without the aid of dye spray and magnification. One-quarter of these lesions are adenomatous and we recommend routine hot biopsy or polypectomy of these lesions.

The prevalence of small, flat colorectal cancers in a western population

OBJECTIVE

Small, flat colorectal cancers have been widely reported in the Japanese literature but are thought to occur rarely outside Japan. The aim of this retrospective cohort study was to clarify the prevalence of flat colorectal cancer in a Western population.

METHODS

One thousand and twenty-six consecutive colonoscopies performed by a single experienced endoscopist were retrospectively analysed over a two-year period. The morphology, site and histological appearance of all documented colorectal cancers (CRC) were recorded.

RESULTS

Forty-seven cases of CRC were detected, five of which (10%) demonstrated flat configuration. Flat cancers varied between 8 and 15 mm in diameter (mean 11 mm). Histologically, all flat lesions were moderately differentiated Dukes A adenocarcinomas. Two of these cancers contained no adenomatous component.

CONCLUSION

This study confirms that small, flat colorectal cancers are not an uncommon finding at colonoscopy in Western patients. Compared to polypoid neoplastic lesions, flat cancers appear to undergo malignant change at a smaller size.

The role of flat and depressed colorectal lesions in colorectal carcinogenesis: new insights from clinicopathological findings in high-magnification chromoscopic colonoscopy

High-magnification chromoscopic endoscopy is a new technique which has been recently introduced to the UK. This technology, initially pioneered by the Japanese in the 1980s, has changed our understanding of the pathogenesis of colorectal cancer and our subsequent therapeutic strategies aimed at the secondary prevention of cancer. Magnification colonoscopic techniques when combined with colonic chromoscopy (dye spraying of the colon) permit in vivo assessments of lesions at a magnification and resolution similar to a stereomicroscope. Furthermore, flat/depressed adenomas and cancers can be diagnosed with increasing frequency and new resection practices performed. This technique is known as endoscopic mucosal resection. As gastrointestinal endoscopists adopt these new techniques, close liaison with histopathologists is essential to provide the highest standards of diagnostic accuracy. The histopathologist also needs to be aware of the endoscopic findings when interpreting specimens and hence must understand new endoscopic terminologies and classification systems that accompany the introduction of new technologies and therapeutic techniques. This article describes the controversies relating to the flat and depressed colorectal lesion, where these new endoscopic technologies are ideally suited. It then provides a working description of high-magnification chromoscopic colonoscopy including the Japanese 'pit pattern' and morphological classification system-information which will be provided to histopathologists with specimens obtained by these new techniques. Finally, we describe the procedure of endoscopic mucosal resection, as the type and quality of specimens received for histopathological analysis will be highly influenced by these techniques.

High-resolution chromoendoscopy for classifying colonic polyps: a multicenter study

BACKGROUND

Chromoendoscopy may reliably separate adenomatous from nonadenomatous polyps. The aim of this multicenter trial was to determine the accuracy of high-resolution chromoendoscopy for the determination of colonic polyp histology.

METHODS

This multicenter trial included 4 academic centers and a primary care practice. In 299 patients referred for routine colonoscopy or sigmoidoscopy, 520 polyps 10 mm in size were sprayed with indigo carmine dye. Using a high-resolution endoscope, the endoscopist predicted the histology of each polyp based on its surface characteristics. Hyperplastic polyps had a "pitted" surface pattern of orderly arranged "dots" that resembled surrounding normal mucosa. Adenomatous polyps had at least one surface "groove" or "sulcus." Each polyp was subsequently resected for histopathologic evaluation.

RESULTS

The resected polyps were comprised by 193 adenomas (37%), 225 hyperplastic polyps (43%), and 102 "other" types (20%). Forty polyps (7.7%) could not be classified by high resolution chromoendoscopy with indigo carmine dye. For the remaining polyps, the sensitivity, specificity, and negative predictive value of indigo carmine dye staining for adenomatous polyps were, respectively, 82%, 82%, and 88%. The results were consistent among the academic centers and the primary care practice.

CONCLUSIONS

High-resolution chromoendoscopy with indigo carmine dye demonstrates morphologic detail of diminutive colorectal polyps that can reliably be used to separate adenomatous from nonadenomatous polyps.

Early detection of colorectal cancer using high-magnification chromoscopic colonoscopy

BACKGROUND

Endoscopic techniques aimed at early detection of colorectal cancer (CRC) and its precursors, permitting targeted in vivo luminal treatments, have been developed by the Japanese since the early 1990s. The introduction of this new technology to the UK (i.e. magnification endoscopes) may permit earlier and more accurate diagnosis. According to Japanese data, magnification chromoscopy can be used to predict histology and invasive depth of cancer, and help in the detection of flat and depressed colonic lesions. Flat and depressed lesions are not purely Japanese phenomena: they exist with a similar incidence in the UK.

METHODS

A Medline search was performed for the years 1955-2001 using the following medical subject headings and search methodology: colorectal cancer and colonoscopy or aberrant crypt foci or molecular kinetics or flat/depressed lesions or chromoscopy.

RESULTS AND CONCLUSION

Early CRC, in the form of flat or depressed lesions, can be difficult to detect using conventional colonoscopic techniques and penetrate the colonic mucosa deeply. The implications of detecting these lesions in relation to current approaches to the prevention of CRC are profound.

Histogenesis and morphogenesis of depressed-type early colorectal carcinoma

The aim of this study was to elucidate the histogenesis and morphogenesis of depressed-type early colorectal carcinomas (DECas). Eighty-seven DECas were selected for examination. The 87 DECas included 23 (26.4%) absolutely depressed (ABS) types (depressed mucosa being thinner than the normal mucosa; histologically true depression), 40 (46.0%) relatively depressed (REL) types (the thickness of the depressed mucosa being the same or greater than that of normal mucosa, with depression being relative compared to marginal elevation) and 24 (27.6%) ulcerated (UL) types (no remnant intramucosal component in the depressed area). The rates of residual adenomatous components were 0/23 (0%) for ABS type and 12/40 (30%) for REL type, indicating that the ABS type was thought to have arisen de novo and the REL type was thought to have arisen de novo and via an adenoma-carcinoma sequence. In 13 of the 23 (56.5%) ABS types, carcinoma was located within the depressed area alone, suggesting that many ABS types show a depression from their initial stage. While 33 of the 40 (82.5%) REL types accompanied by marginal elevation consisted of neoplastic mucosa, in 19 of the 33 (57.6%) cases, the depressed area showed a higher grade of atypia than the area of marginal elevation. This suggested that the depression in the REL type was generated secondarily at the center of a pre-existing, superficially elevated tumor due to progression of its histological grade of atypia. ABS type was speculated to be the precursor of UL type since the two types showed similarity (no statistical significant difference) in percent depression (69.6 vs 64.3%), grade of atypia of carcinoma (52.2 and 79.2% consisted of carcinoma with high-grade atypia alone), and frequency of being accompanied by non-neoplastic reactive marginal elevation (56.5 vs 70.8%).

Prevalence and distinctive biologic features of flat colorectal adenomas in a North American population

BACKGROUND & AIMS

To assess the prevalence of flat and depressed (F&D) colorectal adenomas in the United States, we performed a prospective study of 211 American patients.

METHODS

Dye-assisted colonoscopy was performed in the presence of both an American and a Japanese investigator.

RESULTS

F&D lesions were found in 22.7% of patients, and these were more likely to be adenomatous than polypoid lesions (82% vs. 67%; P = 0.03) and contained more invasive cancer (4.5% vs. 0%; P = 0.04), which also appeared to be at a disproportionately advanced stage. The average size of all F&D advanced lesions (high-grade dysplasia and cancer) was significantly smaller than comparable polypoid lesions (10.75 +/- 2.7 mm vs. 20 +/- 2.9 mm; P < 0.05). F&D adenomas showed significantly stronger fragile histidine triad (FHIT) expression and lower p53 reactivity than similarly sized polypoid adenomas, whereas proliferative and apoptotic indices were similar in both groups.

CONCLUSIONS

We conclude that there is a significant prevalence of colonic F&D colorectal adenomas in this country and that these lesions have significantly different biologic features than polypoid lesions. The clinical and epidemiologic implications of these findings for American patients need to be addressed in further studies.

Cost-utility of one-time colonoscopic screening for colorectal cancer at various ages

OBJECTIVE

One-time colonoscopy has been recommended as a possible colorectal cancer (CRC) screening strategy. Because the incidence of colorectal neoplasia increases with age, the effectiveness and cost of this strategy depend on the age at which screening occurs. The purpose of this study was to investigate the age-dependent cost-utility of one-time colonoscopic screening.

METHODS

We constructed a computer simulation model of the natural history of colorectal neoplasia. This model was used to compare the cost-utility of no screening and age-based strategies employing one-time colonoscopic screening (age ranges evaluated: 45-49, 50-54, 55-59, and 60-64 yr).

RESULTS

We determined that one-time colonoscopic screening in men age <60 yr and in women age <65 yr dominates never screening and screening at older ages. For both sexes, one-time colonoscopic screening between 50 and 54 yr of age is associated with a marginal cost-utility of less than $10,000 per additional quality-adjusted life-year compared to screening between 55 and 60 yr of age. One-time colonoscopic screening between 45 and 49 yr of age is either dominated (women) or associated with a marginal cost-utility of $69,000/per quality-adjusted life-year (men) compared to screening between 50 and 54 yr of age. The marginal cost-utility of one-time colonoscopic screening is relatively insensitive to plausible changes in the cost of colonoscopy, the cost of CRC treatment, the sensitivity of colonoscopy for colorectal neoplasia, the utility values representing the morbidity associated with the CRC-related health states, and the discount rate.

CONCLUSIONS

One-time colonoscopic screening between 50 and 54 yr of age is cost-effective compared to no screening and screening at older ages in both men and women. Screening in men between 45 and 49 yr of age may be cost-effective compared to screening between 50 and 54 yr of age depending on societal willingness to pay.

Clinicopathological features of superficial depressed-type colorectal neoplastic lesions

OBJECTIVE

We performed this study to analyze the endoscopic findings, dissecting microscopic features, and p53 immunostaining in superficial depressed-type (depressed) colorectal neoplastic lesions.

METHODS

Dissecting stereomicroscopy was used to ascertain the size and pit pattern of lesions removed by endoscopic snare polypectomy. Immunohistochemical staining of p53 was performed with an antigen retrieval system using a monoclonal antibody to p53.

RESULTS

All depressed neoplastic lesions (submucosal carcinoma, n = 6; high-grade dysplasia, n = 14; and adenoma, n = 30) were small (< 1 cm in diameter) and were detected as a depression with or without a marginal elevation on colonoscopic examination. In the dissecting microscopic study, submucosal carcinomas and lesions of high-grade dysplasia almost exclusively showed irregular small pits, with the exception of four malignant lesions with moderate submucosal invasion in which the pit structure was absent. In contrast, adenomas had either regular small (29/30 lesions) or oval pits (1/30 lesions). Rates of p53 positivity were 100%, 64%, and 7% in depressed submucosal carcinomas, lesions of high-grade dysplasia, and adenomas, respectively, thus the prevalence of p53 positivity was significantly higher in the former two groups than in the adenoma group.

CONCLUSIONS

The high frequency of invasive carcinoma and high-grade dysplasia found in depressed colorectal neoplastic tumors, despite their small size, indicates that these lesions may be a subtype of colorectal tumor with more aggressive malignant potential at an earlier stage.

In vivo identification of colonic dysplasia using fluorescence endoscopic imaging

BACKGROUND

Previous in vitro studies showed that autofluorescence images of colonic mucosa collected endoscopically can be used to detect dysplasia with high sensitivity. This method is extended to the collection of fluorescence images of adenomatous polyps in vivo.

METHODS

Fluorescence images were collected during colonoscopy in 30 patients. A total of 12 adenomatous and 6 hyperplastic polyps were identified. A fiberoptic excitation probe, located in the instrument channel of the colonoscope, delivered 300 mW of near-ultraviolet light at lambdaex = 351 and 364 nm. Mucosal fluorescence in the spectral bandwidth between 400 and 700 nm was imaged, processed, and displayed with various likelihoods of associated dysplasia.

RESULTS

Adenomatous polyps exhibited decreased fluorescence intensity compared with adjacent mucosa with normal appearance. With the fluorescence threshold set to 80% of the average intensity of normal mucosa, a sensitivity of 83% for dysplasia identification was achieved. All hyperplastic polyps were correctly identified as being non-dysplastic. Optimal identification of dysplastic regions was obtained with the colonoscope oriented at a near-normal angle of incidence to the polyps. At higher angles of incidence, artifacts caused by illumination shadows were introduced.

CONCLUSIONS

The dysplasia associated with adenomatous polyps can be identified in vivo by fluorescence imaging with high sensitivity, thus demonstrating the potential to guide endoscopic procurement of biopsy specimens.

Histopathologic characteristics of advanced colorectal cancer smaller than 2 cm in size

PURPOSE

Screening for colorectal cancer results in an increased incidence of early detection and decreased mortality. Although small colorectal cancer with deep invasion or lymph node metastasis is sometimes encountered, there is no comprehensive study evaluating the histopathologic features of such tumours. The aim of this study was to clarify the characteristics of advanced colorectal cancer <2 cm in size.

METHODS

Using a series of 317 patients who underwent surgery for colorectal cancer, pathologic features were compared among small advanced cancers <2 cm invading the muscularis propria or subserosa (T2, T3) or involving the lymph nodes (N1, N2) (n = 22), small early cancers <2 cm invading only the mucosa or submucosa (T1) without lymph node metastasis (N0) (n = 24), and ordinary advanced cancers> 2 cm (n = 271).

RESULTS

Small advanced cancers were clearly different from small early cancers in gross appearance, histological type, frequency of serosal invasion (18% vs 0%, P < 0.05), lymph node metastasis (36% vs 0%, P < 0.01), and concomitant adenomatous component (17% vs 48%, P < 0.05). Small advanced cancers, when compared with ordinary advanced cancers, were characterized by the grossly superficial type (14% vs 1%, P < 0.01) and absence of serosal invasion (82% vs 14%, P < 0.01) However, the two groups were not significantly different with regard to the frequency of lymph node metastasis (36% vs 53%), liver metastasis (5% vs 15%), and stage of the disease (Dukes' A and B; 64% vs 45%).

CONCLUSION

The results indicate that colorectal cancers, once they invade beyond the submucosa, have the same metastatic potential, irrespective of tumour size. The low frequency of concomitant adenoma implies de novo carcinogenesis of the small advanced cancers.

Rectal cancer after sulindac therapy for a sporadic adenomatous colonic polyp

Like adenomatous polyps in familial adenomatous polyposis, some sporadic colorectal polyps have been reported to regress in response to sulindac administration. However, a rapidly growing invasive rectal cancer developed in one of 15 patients with sulindac-treated sporadic adenomatous colorectal polyps 16 months after sulindac treatment. In this patient, both the adenomatous polyp that responded partially to sulindac and the rectal cancer developing after sulindac therapy showed immunostaining for cyclooxygenase-2. Although short term sulindac therapy seems to be able to cause some adenomatous colorectal polyps to regress, 4 months of sulindac therapy may not reliably prevent colorectal cancer development in these patients.

Invasion depth diagnosis of depressed type early colorectal cancers by combined use of videoendoscopy and chromoendoscopy

BACKGROUND

Depressed type early colorectal cancers are found less frequently than other polypoid cancers although they have a higher submucosal invasion rate. Recently videocolonoscopy and chromoendoscopy have become available and precise descriptions of these lesions are now routine. Because endoscopic mucosal resection is designated for intramucosal and focally extended submucosal (m-sm1) cancers, an evaluation of the characteristic findings indicating invasion depth with these modalities is important.

METHODS

Between January 1991 and March 1996, 64 depressed type early colorectal cancers were detected and treated. When a faint abnormality of the mucosa was suspected by routine videocolonoscopy, 0.1% of indigo carmine solution was sprayed on the mucosal surface (chromoendoscopy). Colonoscopic findings of m-sm1 cancers and moderately and massively extended submucosal (sm2-3) cancers were retrospectively reviewed and compared with confirmed histologic findings.

RESULTS

Characteristic colonoscopic findings needed for surgical operation were as follows: (1) expansion appearance, (2) deep depression surface, (3) irregular bottom of depression surface, and (4) folds converging toward the tumor. By using these findings, the invasion depth of depressed type early colorectal cancers could be correctly determined in 58 of 64 lesions (91%).

CONCLUSIONS

Characteristic colonoscopic findings obtained by a combination of videocolonoscopy and chromoendoscopy are useful for determination of the invasion depth of depressed type colorectal cancers, an essential factor in choosing a treatment modality.