Long-Term Persistence of Carbon Nanoparticle Tattoo Mimicking Pathologic Pigmentation

Case Presentation

A 40-year-old man presented with lower abdominal discomfort for 1 month. He denied using anthraquinone laxatives or gardenoside-containing herbal preparations. Physical examination revealed no irregular pigmented nevi. Laboratory tests revealed a positive fecal occult blood test and an elevated carcinoembryonic antigen (CEA) level of 6.5 ng/mL. Two years earlier, a colonoscopy at another institution had identified and resected a polyp in the descending colon. To rule out malignancy, upper gastrointestinal (GI) endoscopy and colonoscopy were performed. Upper GI endoscopy showed no abnormalities, while colonoscopy showed sharply demarcated black mucosal discoloration in the proximal descending colon, without edema or ulceration ([Fig. 1]). Histopathological examination revealed scattered black particulate deposits within the lamina propria ([Fig. 2]). Perls Prussian blue staining was negative, ruling out hemosiderin deposition ([Fig. 3]). The absence of anthraquinone laxative or herbal use excluded melanosis coli and idiopathic mesenteric phlebosclerosis (IMP). A review of the patient's medical records revealed submucosal injection of carbon nanoparticle suspension (CNS) during the initial polypectomy, which confirmed the diagnosis of CNS-induced pigmentation. After treatment with pinaverium bromide, the patient's symptoms improved, and his CEA level decreased to 2.9 ng/mL. Follow-up colonoscopy 1 year later showed persistent pigmentation at the original site ([Fig. 4]).

Fig. 1 Colonoscopy revealed sharply demarcated black mucosal discoloration in the proximal descending colon, without edema or ulceration.

Fig. 2 Histopathological examination demonstrated scattered black particulate deposits within the lamina propria.

Fig. 3 Perls Prussian blue staining was negative.

Fig. 4 Follow-up colonoscopy performed 1 year later showed persistent pigmentation at the original site.

 

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Practical Implications for Endoscopists

1. CNS, initially developed for lymphatic mapping in oncological surgery, is now increasingly used in endoscopy for lesion relocalization, particularly in high-risk patients who require precise site identification for surveillance.[1] As CNS deposits can persist for over 12 months, the endoscopist may misinterpret the endoscopic findings if unaware of the patient's prior endoscopic treatment history.

2. CNS-induced pigmentation typically manifests as a well-demarcated dark discoloration at the injection site, without significant inflammation.

3. A history of using anthraquinone laxative or gardenoside-containing herbal medicines helps differentiate this condition from melanosis coli[2] and IMP.[3]

4. Histopathological examination is essential for differentiating this condition from malignant melanoma.

 

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Conflict of Interest

None declared.

Authors' Contributions

All authors contributed to the writing of the manuscript.

Patient's Consent

Patient's written consent was obtained for the publication of the case details.

• References

• 1 Wang R, Wang Y, Li D. et al. Application of carbon nanoparticles to mark locations for re-inspection after colonic polypectomy. Surg Endosc 2016; 30 (04) 1530-1533
• 2 Yang N, Ruan M, Jin S. Melanosis coli: a comprehensive review. Gastroenterol Hepatol 2020; 43 (05) 266-272
• 3 Wen Y, Chen YW, Meng AH, Zhao M, Fang SH, Ma YQ. Idiopathic mesenteric phlebosclerosis associated with long-term oral intake of geniposide. World J Gastroenterol 2021; 27 (22) 3097-3108

Publication History

Article published online:
08 September 2025