Splenic Metastases: A Fluorine-18 Fluorodeoxyglucose PET/CT Analysis of Primary Tumor Distribution

Background and aim Splenic metastases are uncommon and typically occur in advanced malignancies despite the spleen's extensive vascular network. This retrospective, single-center cohort study aimed to provide an incidence-based evaluation of splenic metastases in a large PET/CT population and to assess their prognostic implications in contemporary clinical practice. Materials and methods Between January 2018 and December 2024, 41 cases (0.40%) of splenic metastases were identified among 10,295 patients with nonhematologic malignancies undergoing fluorodeoxyglucose (FDG) PET/CT. Metastases were verified through histopathology or, more commonly, through imaging-based criteria supported by longitudinal clinical and radiological follow-up, with consensus evaluation by two experienced nuclear medicine physicians. Maximum standardized uptake value (SUVmax) measurements were obtained for all splenic lesions. Results The mean SUVmax was 8.39 ± 4.03 (range: 3.89-22.22). The most common primary tumors were lung (34.15%), ovarian (21.95%), breast (9.76%), and colorectal (9.76%) cancers. All cases demonstrated concomitant metastatic involvement in other organs, with no isolated splenic metastases observed. Median overall survival was 7.1 months, with one-year and two-year survival rates of 31.7% and 28.2%, respectively. Patients with lung cancer showed significantly poorer overall survival compared to other primary tumors (HR = 2.43, 95% CI: 1.15-5.16, p = 0.020). In multivariate analysis, age and male sex were independently associated with overall survival. Conclusions Splenic metastases are rare (0.40%) in nonhematologic malignancies and are typically associated with widespread metastatic disease. The most common primary tumors are lung, ovarian, breast, and colorectal cancers. Survival is poor following splenic metastasis detection, with a median overall survival of 7.1 months. These findings provide valuable epidemiologic and prognostic data on splenic metastases detected by FDG PET/CT in clinical practice.