To understand the mechanism of spontaneous regression further, we studied the expressions of various oncogenes or tumor suppressor genes, and demonstrated the expression of Maspin. Maspin belongs to the serine protease inhibitor family and may be associated with a favorable prognosis in common salivary gland carcinomas such as adenoid cystic carcinoma, mucoepidermoid carcinoma and carcinoma ex pleomorphic adenoma [11]. Here, SERPINB5 is linked to mucoepidermoid carcinoma.