Concurrent PET/CT detection of giant cell arteritis and high-grade colonic adenoma: a dual diagnostic benefit

Abstract Background Giant cell arteritis (GCA) is the most common large-vessel vasculitis in adults over 50 years of age and may rarely present with ischemic stroke. Its coexistence with premalignant or neoplastic lesions is increasingly recognized, with several studies reporting a temporal association between GCA and both solid and hematologic malignancies. We present a case highlighting the dual diagnostic role of 18 F-FDG PET/CT in detecting both GCA and an incidental colonic adenoma. Case presentation A 70-year-old man was admitted with acute ischemic stroke presenting with amnesia and paraplegia. Brain MRI showed multiple bilateral small ischemic infarcts. Laboratory tests demonstrated elevated C-reactive protein and mild anemia. Thoracoabdominal CT indicated diffuse aortic wall thickening, and temporal artery ultrasound showed bilateral intima-media thickening. Whole-body PET/CT detected FDG uptake along the aorta and major branches, consistent with large-vessel vasculitis, and focal FDG uptake in the sigmoid colon wall without a corresponding CT lesion. Temporal artery biopsy confirmed GCA. The patient received high-dose corticosteroids followed by methotrexate and azathioprine. Colonoscopy, performed due to PET/CT findings, revealed a 3.5 cm villous adenoma with multifocal high-grade dysplasia, which was surgically resected. During five years of follow-up, no GCA relapse or malignant progression occurred. Conclusion PET/CT provided a dual diagnostic benefit by confirming large-vessel GCA and identifying an unsuspected premalignant colonic lesion. This case illustrates the value of comprehensive imaging in elderly patients with systemic inflammation and stroke, while emphasizing the need for cautious interpretation and individualized management.