The aims of the current study are: 1) to study the clinical phenotype of SS patients with leukopenia/neutropenia, 2) to detect anti-neutrophil antibodies in SS patients with leukopenia/neutropenia, and 3) to explore pathogenetic mechanisms of leukopenia/neutropenia in SS patients, linked to the TRAIL pathway and the anti-apoptotic molecule cFLIP. The gene discussed is TNFSF10; the disease is synovial sarcoma.