Rare Site Colonic Metastasis in Renal Cell Carcinoma: Imaging Features on CECT and Multitracer PET-CT Employing 18 F-FDG, 68 Ga-FAPI-04, and 68 Ga-PSMA-11.

This study demonstrates the clinical utility of multitracer positron emission tomography (PET) imaging with 18 F-FDG, 68 Ga-FAPI-04, and 68 Ga-PSMA-11 PET/CT in a rare case of metastatic renal cell carcinoma (RCC) involving the sigmoid colon. A 70-year-old man, who had undergone nephrectomy for T2aN0, RCC in 2019, presented with progressive weight loss and altered bowel habits. Contrast-enhanced computed tomography of the abdomen and pelvis (CECT A+P) revealed a suspicious ulcero-proliferative lesion in the distal sigmoid colon. Functional imaging with 18 F-FDG, 68 Ga-FAPI-04, and 68 Ga-PSMA-11 PET/CT demonstrated focal tracer uptake in the colonic lesion, providing additional evidence suggestive of a neoplastic process. Colonoscopic biopsy subsequently confirmed the lesion to be metastatic RCC. This case highlights the complementary role of multitracer PET imaging in characterizing atypical and rare site metastatic presentations, with its potential theranostic implications.