Thymic mucoepidermoid carcinoma is a rare morphologic variant of primary thymic carcinoma characterized by the presence of squamous cells, mucus-producing cells, and cells of intermediate type.^{1,2,3,4,5,6,7} The neoplasm closely resembles mucoepidermoid carcinomas of other organs and may be associated with multilocular thymic cysts.^4,5,7

Thymic mucoepidermoid carcinoma comprises ˜2% of published thymic carcinoma cases.¹ It tends to occur mostly in middle-aged individuals with a male-to-female ratio of 1.5:1.² Mucoepidermoid carcinomas are not associated with myasthenia gravis except in rare instances.⁸ The initial manifestations include respiratory symptoms and weight loss. Some patients may be asymptomatic.⁴

Grossly, thymic mucoepidermoid carcinomas demonstrate a combination of solid and cystic areas in various proportions.^2,3,4,5,9 The cut surface is white-tan, nodular, and cystic, with fibrous bands and focal mucinous appearance.