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.

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.

Publikationsverlauf

Artikel online veröffentlicht:
08. September 2025

• References

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