A rare case of peritoneal deposits with carbon pigmentation after preoperative endoscopic tattooing for sigmoid colon cancer.

We report a case in which pigmented peritoneal deposits were found during laparoscopic surgery following preoperative endoscopic tattooing for sigmoid colon cancer. The patient's clinical, endoscopic, and histological data from the Niigata City General Hospital were reviewed, as well as the literature on laparoscopic surgery involving the preoperative endoscopic tattoo, with a focus on the relevance of peritoneal deposits and tattooing ink. A 71-year-old man presented to our hospital complaining of vomiting and abdominal distention. Abdominal computed tomography revealed obstructive sigmoid colon cancer. An emergency endoscopic colon stenting procedure and injection of 0.2 ml India ink to the submucosal layer of the tumor's anal side were performed. Laparoscopic-assisted sigmoid colectomy was done 14 days after stenting. At surgery, seven small peritoneal deposits were seen in the rectovesical pouch and at the site adjacent to the tumor. All peritoneal deposits were stained by the ink. Gross leakage of the ink into extraintestinal sites was seen. The seven peritoneal deposits were resected under laparoscope. Histological findings revealed that the seven peritoneal deposits were composed of adenocarcinoma and carbon pigments. Immunohistochemical staining for cluster of differentiation 163 showed that the carbon pigments in the peritoneal deposits were within macrophages. The possibility of the tattooing procedure causing peritoneal dissemination cannot be completely denied, but it can be hypothesized that the carbon pigmentation was transferred to peritoneal deposits by macrophages. In the future, we hope that this phenomenon becomes a keystone for diagnoses and treatments for peritoneal dissemination.