Parotid gland mucoepidermoid carcinoma associated with myasthenia gravis.

Myasthenia gravis (MG) is an autoimmune neuromuscular disease. Although most MG cases do not have accompanying malignant disease, patients with thymoma may have an increased risk for secondary malignancy. The reason MG patients are prone to developing cancer is not very well known. Salivary gland tumors account for approximately 3% of head and neck tumors, and approximately 80% of these occur in the parotid gland. Mucoepidermoid carcinoma is the most common malignant tumor of the parotid gland. MG may be associated with squamous cell carcinoma of the head and neck. We present a patient with MG who developed parotid gland mucoepidermoid carcinoma. MG patients with parotid gland cancer have not been previously reported. We also discuss the possible mechanisms of tumor development in an MG patient.