Fig 1. Microscopic images of primary pulmonary mucoepidermoid carcinoma.

(A) Cross-section of the lobe bronchus demonstrating primary pulmonary mucoepidermoid carcinoma with an endobronchial growth pattern (H&E, lower power). (B) The same case with solid nests and a cystic component that comprises the tumor with hyalinization stroma, foci of calcification, and mucus in the cystic component (H&E, x75). (C) The tumor was composed of mucous, intermediate, and epidermoid cells without keratinization (H&E, x150). (D) Another primary pulmonary mucoepidermoid carcinoma case showing dedifferentiation with severe nuclear atypia, necrosis, and salient mitotic figures (right side) and the upper left corner showing the typical mucoepidermoid carcinoma area (H&E, x150).