Desmoid tumour (aggressive fibromatosis) of the colon mimics malignancy on dual time-point 18F-FDG PET/CT imaging.

A 58-year-old female who presented with a lower gastrointestinal bleed was referred for an (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT after a colonoscopy revealed a submucosal mass in the ascending colon. The PET/CT confirmed the presence of an FDG-avid mass in the ascending colon with no other FDG-avid abnormalities. Dual time-point imaging was performed and showed a significant increase in FDG uptake in the mass, which raised strong suspicion of a colon malignancy. Although an initial biopsy of the mass did not show evidence of neoplasia, a decision was made to proceed with a right hemicolectomy based on high clinical and imaging suspicion of malignancy. Histological evaluation of the hemicolectomy revealed a benign colon desmoid tumour.