Colorectal polyps: when should we tattoo?

Current guidelines recommend tattooing of suspicious-looking lesions at colonoscopy without a reference to the size of the polyp. However, the endoscopist has to make a judgement as to which lesion may be malignant and require future localisation based on the appearance and size of the polyp. The aim of this study was to determine the relationship between endoscopic polyp size and invasive colorectal cancer so as to inform tattooing practice for patients taking part in the national bowel cancer screening programme (BCSP).

Data of BCSP patients who had undergone a polypectomy between October 2008 and October 2010 were collected from a prospectively maintained hospital endoscopic database. Histology data were obtained from electronic patient records.

A total of 165 patients had undergone 269 polypectomies. Their median age was 66 years and 66 % were men. The mean endoscopic polyp size was 10.7 mm (SD = ± 8 mm). Histologically, 81 % were neoplastic with 95 % showing low-grade and 5 % high-grade dysplasia. Eight patients were found to have invasive malignancy within their polyp. The risk of invasive malignancy within a polyp was 0.7 % (1/143) when the endoscopic polyp size was <10 mm; the risk increased to 2.4 % (2/83) when the polyp size was 10-19 mm and 13 % (5/40) when the polyp was >20 mm. This trend was statistically significant (p = 0.001). About 23 % of the patients had the site of their polyp tattooed; the mean size of the tattooed polyps was 21 mm (range = 15-50 mm). Consequently, 25 % of malignant polyps and 63 % of polyps with high-grade dysplasia were not tattooed.

The risk of polyp cancer among BCSP patients increases significantly when the endoscopic polyp size is ≥ 10 mm. We recommend that all polyps ≥ 10 mm be tattooed.