An Enhancing Splenic Lesion Defying Diagnosis

Background: Splenic lymphatic malformations (LMs) typically appear multicystic and nonenhancing on imaging. Deviation from this pattern raises concern for malignancy, a diagnostic challenge compounded in PIK3CA-related overgrowth spectrum (PROS), which predisposes to atypical vascular anomalies. Methods: A 3-year-old boy with a mosaic PIK3CA variant (c.3194A>T) was found to have an incidental splenic mass on surveillance imaging. Multimodality imaging, percutaneous core needle biopsy, and ultimately elective splenectomy with immunohistochemical analysis (D2-40, CD31, CD34) were performed. Results: Magnetic resonance imaging showed a solid, T2-hyperintense, enhancing mass with interval growth. Biopsy suggested lymphangioma but did not explain the solid phenotype. Splenectomy confirmed a splenic LM with intravascular endothelial hyperplasia (IVEH); D2-40 positivity excluded angiosarcoma. Conclusions: IVEH can drive solid, malignancy-mimicking morphology in splenic LMs. In PROS patients, multidisciplinary evaluation, D2-40 staining, and surgical resection for persistent imaging-pathology discordance are essential.