Histologic images of the tumor. (a) Multicystic bland appearance of the tumor, as seen on frozen section (H&E stain, X40). (b) Higher magnification of cystic spaces lined by bland-appearing, flattened cells (H&E stain, X200). (c) In other areas the tumor shows irregular infiltrating glands with fibrous stroma. (d) Highly atypical cells, with hobnail morphology and prominent nucleoli, lining the infiltrating tumor (H&E stain, X400).