The application of endoscopic tattooing of colonic lesions for operative localization was first described in 1975 [3]. Since then, endoscopic tattooing has become the standard procedure for tumor localization.

During tattooing, a needle is used to apply tattoos as it is advanced via the endoscope’s operating channel. To prevent puncturing the serosa, the injection needle is inserted at an angle oblique to the gut wall. The most widely used tattooing agent is India ink, while other substances include methylene blue, indigo carmine, and indocyanine green [4]. The feasibility and safety of autologous blood tattooing have been documented in recent research [5].

Preoperative endoscopic tattooing is more useful and effective for surgery involving left colonic and rectal cancers than for surgery involving right colonic cancers. Regardless of the location of the lesion, the distal resection margin is typically located in the transverse colon during right colon surgery. Thus, endoscopic tattooing is less necessary for these cases. Recent studies have discussed the benefits of endoscopic tattooing, aside from localization of the primary tumor and lymph nodes (LNs).

The retrieval of fewer than 10 LNs has been found to increase the local and distant recurrence rates. Additionally, the quality of LN retrieval was an independent prognostic factor for the survival of colorectal cancer patients [6]. Sinan et al. [7] reported that the number of harvested LNs depended on the preferences of the surgeons and pathologists.

Previous studies have investigated the association between endoscopic tattooing and the reliability of LN retrieval during colorectal cancer surgery [8]. Tattooing improved the accuracy of pathologic staging because LN collection and sentinel node mapping were linked to establishing the diagnosis of LN involvement. Macrophages ingest the carbon particles from the tattoo ink and deposit them in the sinuses of the LNs. This phenomenon induces visible pigmentation that is easily identified by the surgeon and pathologist.

The results of Imaoka et al. [9] contributed greatly to our understanding of endoscopic tattooing in rectal cancers. Their work is unique because there have been few studies on the significance of preoperative tattooing in rectal cancer management. The goal was to determine the value of preoperative tattooing, and they also aimed to identify the most effective predictor of successful LN retrieval. The study compared the collection rate of 12 or more LNs between 49 patients who underwent preoperative tattooing and 43 patients who did not. The former group had a collection rate of 75.5%, while the latter group had a collection rate of 55.8%. Multivariate analysis revealed that female sex, preoperative endoscopic tattooing, and pathologic stage were independent predictors of successful LN collection. Furthermore, according to several studies, obesity, a history of preoperative chemoradiation therapy, and rectal cancer were associated with the retrieval of fewer LNs [10].

This study might have been difficult to carry out because it involved rectal cancer related with fewer LNs retrieval. Its results showed a higher rate of rectosigmoid and upper rectum lesions among the patients who underwent tattooing. However, a higher LN collection rate was expected for the patients who did not undergo tattooing due to the higher incidence of low rectal cancers in this group, because performing successful total mesorectal excision would be more likely among patients with low rectal cancers. However, the actual results contradicted the authors’ expectations. Instead, preoperative endoscopic tattooing allowed the collection of more LNs.

One concern regarding the application of tattooing in rectal surgery is the resulting messy surgical field. Moreover, it remains unclear whether preoperative tattooing might be unnecessary in patients with lesions that can be identified via digital rectal examination. Thus, further studies on the indications for preoperative endoscopic tattooing may be worthwhile and are anticipated.