On the basis of our findings of increased pDCs, a prominent and unique interferon signature, type I interferon activation of dermal fibroblasts to express neutrophil chemokines, and upper dermal localization of fibroblast subsets expressing CXCR2-binding neutrophil chemokines, we speculate that inciting factors drive the production of type I interferon, IL-1, and/or TNF-α in SS. This evidence concerns the gene IL1A and synovial sarcoma.