A Rare Case of Triple Primary Malignant Neoplasms (RCC and Colon Cancer) Detected by ¹⁸F-FDG PET/CT

Multiple primary malignancies are not uncommon in daily oncology practice, even though their frequency in the same or different organ systems varies. Regardless, early detection and proper planning of therapeutic approaches are essential for successful management. Here, we present a 73-years-old male with adenocarcinoma of the sigmoid who was referred for initial staging with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT). ¹⁸F-FDG PET/CT revealed two metabolically active formations in the sigmoid and ascending colon and a large, heterogeneous tumor lesion in the middle and lower third of the left kidney, with increased ¹⁸F-FDG uptake in soft tissue components, suggesting the presence of synchronous neoplasms. The scan also showed ¹⁸F-FDG-positive multiple metabolically active lytic bone lesions with soft tissue components, small pulmonary nodules, and mediastinal/hilar lymph nodes with mildly elevated metabolic activity, suggesting secondary foci. Considering these findings, the patient was referred for histological evaluation.