Sclerosing angiomatoid nodular transformation (SANT) of the spleen is a morphologically distinctive lesion. Although the clinical course of SANT is benign, its reactive or neoplastic nature remains to be clarified. Furthermore, some investigators have suggested that SANT is related to IgG4 sclerosing lesion or inflammatory pseudotumor with stromal cells positive for Epstein-Barr virus (EBV). In this study, we assessed 22 cases of SANT derived from adult women. Clinical data and follow-up information were obtained by chart review. Immunohistochemical studies for IgG4, IgG, and CD21 stains and in situ hybridization to detect EBV-encoded small RNAs were performed. We also assessed genomic DNA extracted from paraffin-embedded tissue for human androgen-receptor α gene analysis using conventional and methylation-specific polymerase chain reaction methods. The median patient age was 41.5 years (range, 25 to 82 y). Most (77%) patients presented with a single mass that was detected incidentally (59%). The mean size of the lesions was 3.8 cm (range, 1.0 to 9.0 cm). Clinical symptoms correlated with multiple lesions (P=0.043) but not lesional size (P=0.637) or location in the spleen (hilum vs. periphery, P=0.696). None of the cases had evidence of IgG4-related disease or recurred after splenectomy. The mean number of IgG4 cells was 27.7 (range, 4 to 125), and the mean IgG4/IgG ratio was 16.4% (range, 1.6% to 55.7%) with only 2 cases being >40%. Cases with higher IgG4 cells did not correlate with inflammatory pseudotumor-like morphology. No lesions were positive for EBV-encoded small RNAs, and almost all cases with informative results (n=19) showed a polyclonal pattern. We conclude that SANT is a polyclonal, reactive lesion rather than a neoplasm.