FDG-avid pulse granulomas mimicking peritoneal metastases in colorectal cancer: a case report

Pulse granulomas are a rare, benign foreign body granulomatous reaction, characterized by hyaline rings, surrounded by multinucleated cells. While typically reported in the oral cavity and lungs, reports on extraoral gastrointestinal manifestations are limited. We present a case on a 72-year-old gentleman with a history of bowel perforation who was found to have a splenic flexure adenocarcinoma on surveillance colonoscopy. Staging imaging showed innumerable fluorodeoxyglucose-avid peritoneal nodules, with concerns of metastatic disease. Diagnostic laparoscopy and peritoneal biopsy found pulse granulomas. The patient had a left hemicolectomy and a final staging of T3N1M0 adenocarcinoma without distant metastases. This case demonstrates pulse granulomas as a rare but relevant mimic of peritoneal metastatic disease in colorectal cancer. Pulse granulomas should be a differential diagnosis of peritoneal nodules in patients with previous mucosal injury. Histopathological confirmation must be pursued to prevent unnecessary surgical intervention or excluding patients from curative treatment.