Fig. 2

Macroscopic and microscopic findings. a The macroscopic appearance of the cut surfaces of the tumor fixed in formalin. Solid and cystic appearance is shown. b–f Microscopic appearance of hematoxylin-and-eosin stained sections of the tumor. The tumor contains typical features of Warthin tumor (b). The tumor shows focal areas of eosinophilic change (c–e, indicated by * in c and e), which suggests coagulation necrosis of the tumor. The periphery of the necrotic area consisted of a non-oncocytic epithelium comprising mucinous and squamous cells (e, f, low and high magnification). Alcian blue staining reveals mucinous cells (g). The squamous cells are diffusely positive for cytokeratin 5, and mucinous cells are negative for this marker (h). In f, g, and h, mucinous cells are indicated by an arrow and squamous cells are indicated by #. i Fluorescence in situ hybridization does not show MAML2 gene rearrangements in the metaplastic component. An inset in i shows a nucleus without MAML2 rearrangement. Bars in a and c represent 3 cm; bars in b, d–h represent 100 μm