Failure of endoscopic detection of a de novo carcinoma of the colon in a patient with adenomatous polyps

Role of colonoscopy in colorectal cancer

Colorectal cancer (CRC) represents the third most common malignancy throughout the world. Little or no improvement in survival has been effectively achieved in the last 50 years. Extensive epidemiological and genetic data are able to identify more precisely definite risk-groups so screening and early diagnosis can be more frequently accomplished. CRC is best detected by colonoscopy, which allows sampling for histologic diagnosis. Colonoscopy is the gold standard for detection of small and premalignant lesions, although it is not cost-effective for screening average-risk population. Colonoscopic polypectomy and mucosal resection constitute curative treatment for selective cases of invasive CRC. Similarly, alternative trans-colonoscopic treatment can be offered for adequate palliation, thus avoiding surgery.

Loss of standard type of CD44 expression in invaded area as a good indicator of lymph-node metastasis in colorectal carcinoma

PURPOSE

Recent advances have made possible the treatment of small invasive colorectal cancer by means of polypectomy or endoscopic mucosal resection. CD44 expression in cancer cells was identified as an indicator of lymph-node metastasis, which could be evaluated in specimens removed by colonoscopy.

METHODS

The correlation between lymph-node metastasis and the expression of standard-type CD44 in cancer cells was examined immunohistologically using the invaded cancer cells of 61 tissue samples of superficially invasive colorectal cancer. We defined the above as invasive cancer restricted within the colorectal wall. Of the 61 samples, 31 had submucosal invasion and 30 had muscular invasion.

RESULTS

Standard-type CD44 expression in the area of invasion in cases with lymph-node metastasis was remarkably down-regulated. In 43 cases with no lymph-node metastasis, 36 (83.7 percent) of patients had CD44 expression in invaded cells, whereas only two of 18 cases (11.1 percent) with lymph-node metastasis had expression of standard-type CD44 in the same area (P < 0.0001). A total of 69.6 percent (16/23) of patients with loss of standard-type CD44 expression in invaded sites were found to have positive metastasis in the lymph nodes. These results suggest that standard-type CD44 in invasive colon cancer cells could suppress metastasis to the regional lymph nodes.

CONCLUSION

In cases of invasive colorectal cancer, the loss of standard-type CD44 expression in the invaded area is a sensitive marker for metastasis to the lymph nodes. Further investigation with larger patient groups is required to clarify the reliability of loss of standard-type CD44 expression as an indicator for additional surgery after endoscopic resection of submucosal invasive colorectal carcinoma.

Early colorectal cancer: flat or depressed type

The present review describes the changes in views about the early forms of colorectal cancers. In 1985, a concept of 'flat adenoma' was born in Japan. At around the same time, depressed type early colorectal cancers started to be reported by Japanese colonoscopists. Neither flat adenomas nor depressed lesions have been frequently reported in Western countries, but increasing numbers of such cases are now described. The problem is that flat adenomas and depressed lesions seem to have been confused by many researchers. The biological aggressiveness of these lesions is quite different. The rate of submucosal invasion is very high in depressed lesions, but fairly low in small flat adenomas. Some adenomas may even look depressed at first, but such lesions should not be mistaken for truly depressed lesions. Ignorance or resistance to the concept may inhibit the detection of flat or depressed lesions. Differences of diagnostic criteria between Japanese and Western pathologists may influence the apparent frequency of mucosal cancers, but not that of invasive carcinomas. Many small adenomas do not grow if followed, but depressed lesions grow rapidly and invade the deeper layers and, as a result, may look elevated as a whole. Many cases in previously published papers suggest that small depressed carcinomas of the large intestine may develop without a precursory stage of an adenomatous polyp. At least two carcinogenic pathways, one through adenomatous polyps and one de novo, should be recognized. In addition, the importance of small depressed cancers should be emphasized.

Differences in the diagnostic criteria used by Japanese and Western pathologists to diagnose colorectal carcinoma

BACKGROUND

In view of the many studies of early stage colorectal carcinoma from Japan, it is essential to know whether the criteria for the histologic diagnosis of colorectal carcinoma are similar in Japan and Western countries.

METHODS

Eight expert pathologists from Japan (4), North America (2), and Europe (2) individually reviewed microscope slides of 20 colorectal lesions from Japanese patients who had undergone endoscopic mucosal resection or surgery because early stage carcinoma and/or adenoma was suspected. The pathologists indicated the pathologic findings on which they based each diagnosis.

RESULTS

For 11 slides that showed adenoma according to the Western pathologists with low grade dysplasia according to at least half of them, the Japanese diagnosed definite carcinoma with or without adenoma in 4 cases and adenoma in 5, and in 2 cases they were equally divided between a diagnosis of adenoma and carcinoma. For five slides showing adenoma with high grade dysplasia according to the Western pathologists, the Japanese diagnosed definite carcinoma with adenoma in three cases and adenoma in one, and in one case they were equally divided between a diagnosis of adenoma and carcinoma. For one case in which the Western pathologists were equally divided between a diagnosis of carcinoma and adenoma with high grade dysplasia, all the Japanese pathologists diagnosed definite carcinoma with or without adenoma. Three slides showed definite carcinoma with or without adenoma, according to both the Western and the Japanese pathologists. The presence of invasion was the most important diagnostic criterion of colorectal carcinoma for the Western pathologists, whereas for the Japanese the nuclear features and glandular structures were more important.

CONCLUSIONS

In Japan, colorectal carcinoma is diagnosed on the basis of nuclear and structural criteria, even in cases considered by Western pathologists to be noninvasive lesions with low grade dysplasia. This diagnostic practice may contribute to the relatively high incidence of early stage colorectal carcinoma reported in Japan as compared with Western countries.

Nonpolypoid adenomas and adenocarcinomas found in background mucosa of surgically resected colons

BACKGROUND

Nonpolypoid (depressed or flat) neoplasias are rarely seen in the colon and rectum. We previously reported their histogenesis and characteristics in patients with familial adenomatous polyposis (FAP), but their development in patients without FAP has not been studied systematically.

METHODS

Three hundred specimens of large intestinal mucosa surgically resected from patients with cancers or other diseases, excluding FAP, were examined with a dissecting microscope. The morphologic types, sizes, locations, and frequencies of detectable colorectal neoplasias, and their histologic features, were analyzed.

RESULTS

A total of 297 adenomas (240 polypoid, 32 flat, and 25 depressed type) were obtained. Nonpolypoid adenomas were most frequently found in the transverse and descending colon. Almost all depressed adenomas (24 of 25; 96%) were less than 3 mm in greatest dimension and almost all flat adenomas (31 of 32; 96.9%) were less than 3.5 mm in greatest dimension. Three minute, nonpolypoid adenocarcinomas (mean size, 2.6 mm; range, 2.4-2.9 mm) were also detected, two of them already invaded the submucosal layer.

CONCLUSIONS

Minute nonpolypoid type adenomas may be present in the background mucosa of patients without FAP. This study suggests that even minute nonpolypoid adenocarcinomas have an increased potential for endophytic growth.

Endoscopic treatment of submucosal invasive colorectal carcinoma with special reference to risk factors for lymph node metastasis

A clinicopathological analysis of the risk factors for lymph node metastasis was performed in 177 patients with submucosal invasive colorectal carcinoma (CRC). The submucosal deepest invasive portion was histologically subclassified as well (W), moderately (M), or poorly (Por) differentiated. M type was further subdivided into moderately-well (Mw) and moderately-poorly (Mp) differentiated. The pattern of tumor growth was classified as polypoid growth (PG) and non-polypoid growth (NPG). Lymph node metastasis was detected in 21 (12%) of the 177 patients. Macroscopically, type IIc and IIa + IIc lesions showed a significantly higher incidence of lymph node metastasis (44% and 30%) than type IIa and I (4% and 8%). Regarding the histologic subclassification, Por and Mp lesions showed a significantly higher incidence of lymph node metastasis (67% and 37%) than W and Mw lesions (4% and 14%). NPG tumors showed a significantly higher incidence of lymph node metastasis (29%) than PG tumors (7%). The depth of submucosal invasion and lymphatic invasion (ly) were also significantly correlated with the incidence of lymph node metastasis (submucosal scanty (sm-s) invasion 4%, massive invasion 20%; ly(+) 23%, ly(-) 5%). None of the lesions with both sm-s invasion and of W or Mw type showed lymph node metastasis. These results indicate that submucosal invasive CRC with both sm-s invasion and of W or Mw type, which shows no ly, is the appropriate indication for endoscopic curative treatment.

The adenomatous polyposis coli gene and human cancers

The APC (adenomatous polyposis coli) gene was isolated as a gene responsible for familial polyposis coli, an autosomal-dominant disease, characterized by development of hundreds to thousands of adenomatous polyps in the colon and rectum. However, recent studies revealed that inactivation of the APC gene also plays a significant role in development of sporadic forms of colorectal adenoma and carcinoma. Furthermore, somatic mutations have also been detected in pancreatic carcinomas as well as some type of gastric carcinomas, suggesting that APC has a critical function in regulation of cell growth in digestive tissues.

Small flat cancer of the rectum: clinicopathologic and endoscopic features

The clinicopathologic and endoscopic features of 15 patients with small flat cancer of the rectum were investigated. Whereas 4 patients had hematochezia, the remaining 11 patients were asymptomatic, and stool positive for occult blood was the only remarkable clinical feature in 8 of them. Endoscopic features were slight elevation with central depression in 8 lesions, flat-topped elevation in 4, and shallow depression with irregular margin in 3. The surface of the tumor was often faint red in color and frequently characterized by mucosal friability. Five flat rectal cancers were missed during initial endoscopy, and they were found by repeated endoscopic examination. Three flat cancers were not identified in the distal rectum until retroflexed colonoscopic observation was performed. Although all tumors were smaller than 2 cm in diameter and 6 of them were under 1 cm, 9 lesions had deeply invaded the submucosal layer and 7 tumors showed lymphovascular permeation. Two lesions of 1 cm or greater had metastasized to perirectal lymph nodes. These results suggest that careful observation during endoscopy is necessary to detect flat rectal cancers, and a U-turn to examine the anorectal junction should be routinely done in the appropriate age group.

Flat neoplastic lesions of the colon and rectum detected by high-resolution video endoscopy and chromoscopy

Because small flat colorectal neoplastic lesions (i.e., flat adenomas and flat adenocarcinomas) may be as translucent as the surrounding mucosa, they can remain undetected at conventional endoscopy. By combining high-resolution video endoscopy and chromoscopy, we detected 109 colorectal flat neoplastic lesions in 55 of 232 patients studied. Forty-three (78%) of the 55 patients with flat neoplastic lesions were over 60 years of age. No flat neoplastic lesions were seen in patients under 40 years of age. Flat neoplastic lesions were more frequent in men (35%) than in women (15%). Seventy-seven (71%) of the 109 flat neoplastic lesions measured 0.5 cm or less, 23 (21%) between 0.6 and 1.0 cm, and 9 (8%) more than 1.0 cm. Low-grade dysplasia and high-grade dysplasia were found in 94 (86%) and 13 (12%) of the flat neoplastic lesions, respectively. Adenocarcinoma was diagnosed in 3 (3%) flat lesions: 1 (1%) carcinoma originating in a flat adenoma and 2 (2%) adenocarcinomas without recognizable adenomatous elements. No adenocarcinomas were seen in lesions measuring 1.0 cm or less. Fourteen flat neoplastic lesions had a central depression at endoscopy. Flat neoplastic lesions with central depression more frequently showed high-grade dysplasia (43%) than did flat neoplastic lesions without central depression (7%). Central depression in flat neoplastic lesions should be considered a possible endoscopic marker for severe dysplasia. Our results suggest that flat neoplastic lesions occur more frequently than previously reported in Scandinavia. Flat adenomas may play an important role in the histogenesis of colorectal cancer.

Minute flat depressed neoplastic lesions of the colon detected by contrast chromoscopy using an indigo carmine capsule

Thirty-seven diminutive flat depressed neoplastic lesions of the colon, smaller than 5 mm, were detected by contrast chromoscopy using an indigo carmine capsule and subsequently removed by endoscopic mucosal resection. We investigated the endoscopic, macroscopic, and histologic characteristics of these lesions and also evaluated the usefulness of chromoscopy and the magnifying endoscope for detecting this type of lesion. The lesions were classified into two types according to the measured height of the histologic sections: 28 lesions were truly flat depressed and the remaining 9 lesions were flat elevated. Of the 37 lesions, 18 were adenomas with mild atypia, 14 with moderate atypia, and 5 with severe atypia. The flat depressed lesions included 12 with mild atypia, 11 with moderate atypia, and 5 with severe atypia. No invasive carcinoma was present in either type, and no adenoma with severe atypia was identified in any of the flat elevated lesions. The overall rate of severe atypia was 13.5%; the rate of severe atypia for the flat depressed type was 17.9%, which is approximately 14-fold greater than that of ordinary diminutive polypoid adenomas (1.3%). The detection of these lesions was facilitated by the use of indigo carmine dye, which clearly demonstrated the mucosal irregularities. The frequency of detection of these lesions was increased four to five times with a magnifying endoscope, as occurred in nearly 10% of all of the patients examined. These data suggest that the finding of endoscopically minute flat depressed neoplastic lesions is not at all uncommon when examination is meticulously performed.(ABSTRACT TRUNCATED AT 250 WORDS)

A clinicopathologic study of small flat colorectal carcinoma

BACKGROUND

Recent studies have noted that small flat carcinomas do exist in the human colon, but their clinicopathologic features have not been fully delineated.

METHODS

A clinicopathologic study of 62 flat colorectal carcinomas (FCC) and 80 polypoid colorectal carcinomas (PCC) was performed. FCC were defined for the study as colorectal adenocarcinomas confined to the mucosa or submucosa, macroscopically characterized as slightly elevated, often nearly flat, and sometimes with central shallow depressions.

RESULTS

In intramucosal and submucosal invasive carcinomas, the mean size of FCCs was significantly smaller than that of PCCs, (P < 0.001). When compared with PCCs, FCCs were found more often in the proximal colon, less frequently well differentiated, and had fewer adenomatous remnants. In submucosal invasive cases, FCCs showed more frequent deep invasion (67 versus 32%, P < 0.05) and lymphovascular permeation (41% versus 16%, P < 0.05) compared with PCCs.

CONCLUSIONS

These results suggest that FCCs are characterized by frequent deep invasion with lymphovascular permeation even when small, and that they may be more prevalent away from the rectosigmoid area.

APC and p53 mutations in de novo colorectal adenocarcinomas

To investigate genetic features in small and flat colorectal carcinomas that arise de novo, we searched for genetic alterations in six sporadic tumors by examining their APC, K-ras, and p53 genes. Two of the six tumors carried detectable mutations within the mutation cluster region (MCR) of the APC gene; both mutations were predicted to cause truncation of the gene product. Four tumors carried mutations of the p53 gene; three were missense mutations in exon 5, and the other was a 3-bp deletion in exon 6. However, neither codon 12 nor codon 13 of K-ras contained detectable mutation in any tumors. Hence, as "adenoma-carcinoma sequence" model of development of colorectal carcinoma, inactivation of the APC and p53 genes appear to be involved in development of the de novo type of colorectal carcinoma even though the adenoma stage is not observed.