The following novel findings were obtained: (1) salivary EGF levels in SS patients were significantly lower than those in non-SS patients; (2) salivary EGF levels as well as the salivary flow rate decreased with the progression of SS; (3) with prolonged SS disease duration, salivary EGF levels decreased more rapidly than the salivary flow rate; and (4) decreases in salivary EGF levels significantly correlated with exacerbation of the oral health-related QoL in patients with SS. Here, EGF is linked to synovial sarcoma.