EPITHELIAL MISPLACEMENT AFTER BIOPSY OF COLORECTAL ADENOMAS

The question has been raised as to whether the removal of biopsy mater ial from colorectal adenomas can lead to misplacement of tumour fragme nts into the deeper layers of the bowel wall. We carried out an analys is of histological sections obtained from 21 patients in whom, between 2 and 21 days before removal of their adenoma, forceps biopsy (n = 18 ), or polypectomy (n = 3) had been performed. The initial histological picture a few days after biopsy is of an ulcer covered by a suppurati ve exudate and abundant mucus-containing small, free-lying groups of t umour cells. After an average of 7 days, we found misplacement of thes e groups of cells into the submucosa where, during the course of repar ative processes, they became embedded within a capillary-rich granulat ion tissue. Subsequently, fibrosis of the submucosa develops with pers istent mucus pools. Our results thus show that removal of biopsy mater ial from adenomas can result in misplacement of tumour particles into the submucosa. These changes were observed in flat or broad-based tumo urs, and epithelial misplacement appears to be detectable within only a short period after biopsy. For the differential diagnosis, it is imp ortant to distinguish these changes from invasive carcinoma.