Flat and depressed colorectal tumours in a southern Swedish population: a prospective chromoendoscopic and histopathological study

Abstract

Background: Flat and depressed colorectal tumours are common in Japan but are very rare or non-existent in Western countries.

Aims: To study the occurrence of flat colorectal tumours in a southern Swedish population.

Methods: In this prospective study, 371 consecutive European patients were examined by high resolution video colonoscopy combined with chromoendoscopy. The nature of the lesions was determined by histopathological examination.

Results: A total of 973 tumours were found; 907 (93.2%) were protruding and 66 (6.8%) were flat or depressed. Of the flat/depressed tumours, five (7.7%) were early adenocarcinomas infiltrating the submucosa. Eleven carcinomas (1.2%) were found among protruding tumours. High grade dysplasia was observed in 18% (n=11) of flat/depressed adenomas in contrast with 7.3% (n=65) of protruding adenomas, and occurred in smaller flat/depressed tumours compared with protruding ones (mean diameter 8 mm v 23 mm, respectively). Furthermore, high grade dysplasia was significantly more common in flat elevated tumours with central depression or in depressed adenomas (35.7%; 5/14) than in flat elevated adenomas (12.8%; 6/47).

Conclusion: Flat and depressed tumours exist in a Western population. Future studies should address whether or not chromoendoscopy with video colonoscopy is necessary in the search for flat colorectal neoplasms.

Figure 1

Flow scheme of patients, colonoscopies, and tumours. FAP, familial adenomatous polyposis; HNPCC, hereditary non-polyposis colorectal cancer; IBD, inflammatory bowel disease.

Figure 2

(A) Endoscopic view of a IIc+IIa lesion, 3 mm in diameter before dying. The lesion (between the arrows) was discovered by its slight redness. (B) Chromoendoscopic view of the same tumour (between the arrows): following dye spraying the depression was clarified and slight marginal elevation was noted. (C) Low power histological view of the same tumour (between the arrows) showing depression. The central “protrusion” is the result of tangentional sectioning. Haematoxylin and eosin, ×40

Figure 3

High power view of the superficial part of a flat adenoma. The nuclei are enlarged, vesicular, and rounded containing large nucleoli. There is also clear stratification with at least three layers of nuclei above each other. There is no sign of mucin secretion apart from a few goblet cells. These changes represent high grade dysplasia. No sign of invasion was seen within this tumour. Haematoxylin and eosin, ×380.

Figure 4

Low power view of a flat carcinoma with invasion of the submucosa (arrows). Haematoxylin and eosin, ×40.