Fig. 2

Macroscopic and microscopic findings. a Cut surface of the surgical specimen. The tumor size was 2.7 × 1.9 × 1.8 cm, whitish–yellow to gray, shiny and well-demarcated. b The tumor consisted of duct-like structures and polygonal and spindle cell features. c The duct-like structures comprised two distinct cell layers. The inner-layer cells were composed of cuboidal cells with eosinophilic cytoplasm and round nuclei, and the outer-layer cells (black arrow) were composed of cells with clear cytoplasm and oval-to-fusiform nuclei. d The polygonal and spindle cells (black arrow head) were similar to the outer-layer cells (black arrow) and had clear cytoplasm