Colorectal tumours and pit pattern

The impact of new technology on surgery for colorectal cancer

Advances in technology continue at a rapid pace and affect all aspects of life, including surgery. We have reviewed some of these advances and the impact they are having on the investigation and management of colorectal cancer. Modern endoscopes, with magnifying, variable stiffness and localisation capabilities are making the primary investigation of colonic cancer easier and more acceptable for patients. Imaging investigations looking at primary, metastatic and recurrent disease are shifting to digital data sets, which can be stored, reviewed remotely, potentially fused with other modalities and reconstructed as 3 dimensional (3D) images for the purposes of advanced diagnostic interpretation and computer assisted surgery. They include virtual colonoscopy, trans-rectal ultrasound, magnetic resonance imaging, positron emission tomography and radioimmunoscintigraphy. Once a colorectal carcinoma is diagnosed, the treatment options available are expanding. Colonic stents are being used to relieve large bowel obstruction, either as a palliative measure or to improve the patient’s overall condition before definitive surgery. Transanal endoscopic microsurgery and minimally invasive techniques are being used with similar outcomes and a lower mortality, morbidity and hospital stay than open trans-abdominal surgery. Transanal endoscopic microsurgery allows precise excision of both benign and early malignant lesions in the mid and upper rectum. Survival of patients with inoperable hepatic metastases following radiofrequency ablation is encouraging. Robotics and telemedicine are taking surgery well into the 21^st century. Artificial neural networks are being developed to enable us to predict the outcome for individual patients. New technology has a major impact on the way we practice surgery for colorectal cancer.

Magnifying colonoscopy in differentiating neoplastic from nonneoplastic colorectal lesions

OBJECTIVE

Because the medical management of persons with adenomatous colorectal polyps differs from that of those with hyperplastic polyps, accuracy of diagnosis is essential. This study reports our experience using a magnifying colonoscope combined with indigocarmine dye to diagnose colorectal polyps, emphasizing its ability to differentiate neoplastic from nonneoplastic lesions.

METHODS

The materials consisted of 175 polyps. A 0.2% indigocarmine solution was sprayed, and the colonoscope zoom apparatus performed a magnified observation after an ordinary colonoscopy identified the lesions. The pit patterns were classified into six categories: I, II, III(L), IIIs, IV, and V according to Kudo's modified classification.

RESULTS

The percentages of neoplastic changes in the lesions with pit pattern I, II, III(L), IIIs, IV, and V were 0, 12.2, 69.7, 80, 84.4, and 100%, respectively. The diagnostic sensitivity of neoplastic lesions was 93.8% and specificity was 64.6% when types I and II represented the pit pattern of nonneoplastic lesions and types III(L), IIIs, IV, and V represented neoplastic lesions. The overall diagnostic accuracy in differentiating neoplastic from nonneoplastic lesions was 80.1%. The diagnostic accuracy is not influenced by the size and shape of the lesions. The six neoplastic lesions that were misjudged to be nonneoplastic were histologically adenoma with only mild atypia.

CONCLUSIONS

The pit pattern analysis of colorectal lesions by magnifying colonoscopy is a useful and objective tool for differentiating neoplastic from nonneoplastic lesions of the large bowel. In its current state of development, however, this technique is not a substitute for histology.

Laterally spreading tumor: clinicopathological study in comparison with the depressed type of colorectal tumor

AIM

To evaluate the difference between laterally spreading colorectal tumors (LSTs) with depression and depressed-type colorectal tumors.

METHODS

Sixteen LSTs showing the appearance of non-distinct, gently sloping central depressions were compared clinicopathologically with 14 depressed-type tumors that were larger than 10 mm in size.

RESULTS

The mean size of LSTs with depression was 13.5 +/- 3.4 mm, which was significantly larger than that of the depressed type colorectal tumors (11.2 +/- 1.5 mm). The invasion of the depressed-type colorectal tumors was significantly deeper than that of LSTs with depression, despite the larger size of the LSTs. The surface structures (pit patterns) of both types of tumors were apparently different; the pit patterns of LSTs with depression were almost of the type IIIL pit, while that of the depressed-type tumors were almost of type V pits (P < 0.01). Histologically, LSTs with depression appeared to grow in a superficial replacing manner on the edge of the lesions, while depressed-type tumors grew in an expanding manner.

CONCLUSION

It seems appropriate that these LSTs with depression should be distinguished from depressed-type colorectal tumors and regarded as constituting a new clinical entity.

[Magnifying colonoscopy in the diagnosis of colorectal carcinoma invading the submucosa in familial adenomatous polyposis]

The development of colonoscopy with image magnification has enable to study the colonic mucosa in detail and to do differential diagnosis between neoplastic and non-neoplastic lesions from the observation of pit patterns. The results are comparable to stereomicroscopy being possible to predict the histologic diagnosis. In a patient with familial adenomatous polyposis magnifying colonoscopy was performed and this method demonstrated a wide variation of benign polypoid lesions and the morphological features of early colorectal cancer. In this patient, the evaluation by image magnification, together with indigo carmin 0.4% chromoscopy, showed a wide variety of lesions in the colon and rectum: laterally spreading tumor in the cecum, with IIIL + IV pits, subpediculate polyp in the transverse colon with approximately 2.0 cm diameter and IV + V pits, flat elevated lesions IIIL type, and in the sigmoid colon IIa + IIc lesion with V type of Kudo's classification were observed. The evaluation of pit patterns of the lesions in the transverse and sigmoid colon has enable to do the endoscopic diagnosis of the lesion with submucosal invasion.

Efficacy of magnifying endoscopy in the differential diagnosis of neoplastic and non-neoplastic polyps of the large bowel

PURPOSE

We have introduced magnifying colonoscopy into clinical practice and analyzed its diagnostic efficacy, especially regarding the ability to distinguish neoplastic from non-neoplastic polyps.

METHODS

The materials consisted of 923 polyps. After identifying the lesions during normal colonoscopy, a dye was sprayed, and then the zoom apparatus of the colonoscope was used to make a magnified observation at a maximum 100 times magnification. We classified the crypt orifices into six categories and labeled them A to F as follows: A, a medium round appearance; B, an asteroid appearance; C, an elliptic appearance; D, a small, round appearance; E, a cerebriform appearance; F, no apparent structural appearance.

RESULTS

Forty-two of 923 polyps did not reveal any clear images of crypt patterns. The percentage of histologically neoplastic change in the lesions classified as A, B, C, D, E, and F were 10, 15.9, 93.7, 100, 94.8, and 87.5 percent, respectively. When we considered types A and B to represent a crypt pattern of non-neoplastic lesions, and types C, D, E, and F to represent neoplastic lesions, and when the lesions that did not show any clear images were classified as a misjudgment, the diagnostic accuracy of neoplastic lesions (sensitivity) was 92 percent and that of non-neoplastic lesions (specificity) was 73.3 percent. Overall, the diagnostic accuracy in differentiating neoplastic from non-neoplastic lesions was 88.4 percent. Twenty-three neoplastic lesions that were misjudged to be non-neoplastic were histologically adenoma with mild atypia in 22 and adenoma with moderate atypia in 1.

CONCLUSION

Magnifying colonoscopy was considered to be useful in determining the indications for colonoscopic removal.

In vivo observation of the ileal microadenoma in familial adenomatous polyposis

Microadenomas or aberrant crypt foci (ACFs) are regarded as early neoplastic lesions that precede the development of macroscopic adenomas. The aim of this study was to characterize surface features of ileal microadenomas in patients with familial adenomatous polyposis (FAP). Magnifying ileoscopy was performed in 19 patients with FAP. A histologically verified adenomatous tubule, the existence of which was suggested by magnified observation, was regarded as a microadenoma. Magnifying ileoscopy detected microadenoma in five patients. In four of the five cases, the ileal microadenomas were identified as areas with tiny crypt openings or serrated surfaces, which were distinctive of nonneoplastic, diminutive protrusions. Magnifying ileoscopy seems to be useful in the detection of ileal microadenomas.

Correlation of lifting versus non-lifting and microscopic depth of invasion in early colorectal cancer

BACKGROUND

The non-lifting sign is considered a contraindication to endoscopic resection. Our objective was to investigate whether lifting or nonlifting of a lesion is determined by the volume of normal submucosal tissue.

METHODS

We measured the thickness of the submucosa and examined the relation between submucosal invasion and lesion elevation induced by submucosal injection in 60 patients with colorectal cancer with evidence of submucosal invasion. Extent of tumor elevation was classified into two groups: A, lifting; B, non-lifting. Submucosal invasion was classified as sm1, sm2, or sm3. The distance between the carcinoma and the line of resection and that between the carcinoma and the muscularis propria were measured.

RESULTS

Of 31 sm1 lesions, 29 (93.5%) were group A. All 6 sm3 lesions were group B. All lesions in group A had a value for the distance between carcinoma and muscularis propria of more than 1000 microm. Group B lesions with sm3 invasion had distances of only 105 to 750 microm.

CONCLUSION

Lesions classified as sm3 do not elevate in response to submucosal injection, and lesions that become elevated on injection can be resected endoscopically because they are sm1 or sm2 and have a thickness of normal submucosa of more than 1000 microm.

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.

Marginal irregularity of flat elevated type of colorectal tumor as a marker of malignant potential

BACKGROUND

The malignant potential of superficial elevated type tumors is still controversial. Because biopsy specimens alone are sometimes not sufficient for diagnosis due to histologic heterogeneity within the tumor, other clinical parameters for evaluation of the degree of malignancy would be helpful.

METHODS

A new morphometric parameter, the "F-circle," which represents the irregularity of the tumor margin, was studied in 115 endoscopically recognized superficial, flat, elevated type colorectal tumors without a central depressed area with respect to histologic evaluation of the degree of malignancy.

RESULTS

The mean F-circle values of adenomatous lesions with mild or moderate atypia, severe atypia, and adenocarcinoma were 0.709+/-0.115, 0.619+/-0.149, and 0.536+/-0.133, respectively.

CONCLUSION

The superficial elevated type of colorectal tumor having more marginal irregularity had a greater malignant potential, and the F-circle may be a useful clinical parameter for evaluation of the degree of malignancy.

High frequency of K-ras mutations in human colorectal hyperplastic polyps

BACKGROUND

Hyperplastic polyps are common benign colorectal polyps, and are thought to have little association with malignant tumours in the colorectum. However, several reports suggest that some hyperplastic polyps may develop into colorectal neoplasms.

AIM

To clarify genetic alterations in colorectal hyperplastic polyps.

METHODS

Twenty eight colorectal polyps having serrated components were resected from patients endoscopically. The K-ras gene mutations in codons 12 and 13 were analysed by PCR-RFLP. Intranuclear p53 protein was immunostained by the avidin-biotin complex method.

RESULTS

A mutation of the K-ras gene was detected in nine (47%) of 19 hyperplastic polyps, and five (56%) of nine adenomas. p53 protein nuclear accumulation was detected immunohistochemically in two (22%) of nine adenomas, but not in any of the hyperplastic polyps.

CONCLUSION

Some hyperplastic polyps may be true neoplastic lesions, and could be precursors of malignant neoplasia.

p53 immunoreactive stain and early colorectal adenocarcinomas

565 cases of early colorectal adenocarcinomas were used in this study to examine mechanisms of carcinogenesis. Specimens were paraffin embedded and histological sections were stained with haematoxylin-eosin and p53. Macroscopically, early colorectal adenocarcinomas could be classified into two types: protruding and depressed. The former were composed of branching glands, while the latter were composed of straight glands which opened to the surface. The p53 positive ratio was similar for protruding tumours but was higher in depressed submucosal invasive adenocarcinomas than in depressed intramucosal adenocarcinomas. These results raise the possibility of at least two pathways for colorectal carcinogenesis, adenoma-carcinoma lesions and de novo carcinoma lesions.

The problem of de novo colorectal carcinoma

From April 1985 to March 1995, colonoscopy was carried out at our institution in 24,059 patients, 31,800 times in symptomatic and/or asymptomatic average risk persons. 184 submucosal invasive carcinomas were detected. Unlike protruding-type lesion, the depressed-type invades the submucosal layer, even though the size is within 10 mm. The depressed type of invasive carcinoma accounted for 20 lesions, and represented 10.9% (20 of 184) of all the invasive carcinomas. The pit pattern of depressed-type lesions shows a small round pit (type IIIs pit pattern) and that of carcinoma lesions shows the irregular pit and non-structure (type V pit pattern).