F-18 FDG PET-CT findings of intraperitoneal carbon particles-induced granulomas mimicking peritoneal carcinomatosis

F-18 FDG PET-CT is a useful modality for monitoring residual or recurrent tumors after surgical resection. We report on 3 patients with intraperitoneal charcoal-induced granulomas mimicking peritoneal carcinomatosis on PET-CT images. Two of them underwent a radical gastrectomy because of advanced gastric cancer, and the other underwent a hemicolectomy because of sigmoid colon cancer. All 3 patients had a history of intraperitoneal chemotherapy using mitomycin C bound to activated carbon particles during surgery. Follow-up PET-CT studies demonstrated increased FDG uptake mimicking peritoneal carcinomatosis on PET images alone. However, the accompanying noncontrast CT showed variously shaped hyperdense nodules in the dependent positions of the peritoneal cavity, including the paracolic gutter and rectovesical space, indicating charcoal-induced granulomas rather than peritoneal carcinomatosis.