Parenchymal Splenic Metastases from Solid Malignancies: Imaging Characterisation on ¹⁸ F-FDG PET/CT — A Case Series

Parenchymal splenic metastases from solid malignancies are infrequent, often clinically silent, and usually present in the setting of widespread systemic metastases. Imaging characterisation is limited and challenging because of overlapping features with inflammatory pathologies and primary splenic neoplasms. This retrospective case series included six patients with solid malignancies who demonstrated splenic lesions on 18F-FDG PET/CT between 2016 and 2025. Imaging was evaluated for morphology, metabolic activity (SUVmax), and extra-splenic disease. Histopathological confirmation was available in one operated case, while the diagnosis in the remaining patients was based on imaging and clinical context. Primary malignancies included renal cell carcinoma (n = 2), breast carcinoma (n = 1), lung carcinoma (n = 1), hepatocellular carcinoma (n = 1), and ovarian carcinoma (n = 1). Splenic lesions were associated with systemic metastatic disease in most patients. Lesions were isodense to hypodense on CT and showed variable FDG uptake (SUVmax range: ~3.8 -15.5). In patients with widespread disease, splenic involvement was interpreted as metastatic based on imaging patterns. Histopathological confirmation was available in one case. 18F-FDG PET/CT unveils clinically occult splenic metastases and provides whole-body disease burden. Although imaging patterns, along with clinical context, may suggest metastatic disease, histopathological confirmation is recommended for solitary or indeterminate lesions, as it may contribute to therapeutic decision-making.