Fig. 3. (A) Macroscopic appearance of the resected specimen showing a tumor within the cyst (white arrowhead) and the remaining cyst wall (black arrowhead). (B) Microscopic appearance of the mucoepidermoid carcinoma arising in a bronchogenic cyst (white arrowhead) and a cyst wall lined by ciliated columnar epithelium (black arrowhead) (HE stain × 40). (C) Detail of Figure 3 (B) (HE, × 100). (D) Alcian blue stain, a stain helpful for establishing the diagnosis of mucoepidermoid carcinoma, highlighting the presence of cytoplasmic mucin in the tumor cells. HE: hematoxylin and eosin.