Epithelial misplacement in the muscularis propria after biopsy of a colonic adenoma

Abstract

Sir, Hyper-plastic and hamartomatous colonic polyps may show misplaced epithelium (pseudo-invasion) within the submucosa or more rarely even extending into the muscular wall and/or serosa, potentially simulating an invasion by a well-differentiated adenocarcinoma [2, 4]. The pathogenesis of this condition is referred to as the passage of the mucosal glands through the anatomical defects in the muscularis mucosae due to tissue damage from torsion, or twisting, of the polyp [2, 4]. It is likely that even minor trauma, resulting from vigorous peristalsis or bulky intraluminal material, may be responsible of epithelial misplacement, especially in sessile polyp [4]. Pseudo-invasion can also commonly occur in peduncolated adenomatous polyps, especially in the form of herniated mucosal glands through natural spaces in the muscularis mucosae, into the sub-mucosa of the polyp stalk [3]. Although it is known that transient epithelial misplacement in the sub-mucosa can occur in colonic adenomas within a short period after biopsy [1], to the best of our knowledge, an extension into the muscularis propria has not been reported to date. We first report an epithelial misplacement (pseudoinvasion) in the muscularis propria after an endoscopic biopsy of a sessile colonic adenoma. An 86-year-old man underwent colonoscopy for rectal bleeding. A large broad-based polypoid mass was found in the sigmoid colon, and bioptic material was obtained for histological examination. Histologically, the removed fragments were consistent with an adenoma with low-grade dysplasia. Because of the large dimension of the tumour, surgical resection (sigmoid colon and upper rectum) was performed after 12 days from biopsy. Grossly, a broad-based polypoid mass, measuring 4.5 cm in diameter, was observed in the sigmoid colon. The tumour was entirely sampled and processed for microscopic examination. Histologically, the tumour was a tubulovillous adenoma with low-grade dysplasia. At the base of the tumour, mucosal ulceration covered by a mixture of mucus lakes and suppurative exudate with isolated free-lying glands could be noted (Fig. 1a). It is surprising to note that isolated atypical glands were found in the underlying muscularis propria (Fig. 1b). Cytologically, the glandular epithelium was composed of atypical mucin-depleted cells with enlarged, vesicular, oval to round nuclei containing small nucleoli. These glands were completely enveloped by granulation tissue containing inflammatory cells, newly formed capillaries and a minor amount of fibroblasts (Fig. 1b). Despite additional histological sections prepared from deeper levels of the tissue blocks, foci of malignant transformation were not identified. It was possible to identify a continuous rim of granulation tissue in only one section, extending from the mucosal ulceration at the base of the tumour into the sub-mucosa and muscularis propria. Isolated atypical glands, cytologically similar to those formerly observed, were entrapped at different levels (from mucosa to muscularis propria) within the abovementioned granulation Virchows Arch (2007) 450:603–605 DOI 10.1007/s00428-007-0399-2

DOI: 10.1007/s00428-007-0399-2

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Cite this paper

@article{Magro2007EpithelialMI, title={Epithelial misplacement in the muscularis propria after biopsy of a colonic adenoma}, author={Gaetano Magro and Giuseppe Aprile and Giuseppe Vallone and Paolo Greco}, journal={Virchows Archiv}, year={2007}, volume={450}, pages={603-605} }