Fig. 2

Histological findings of the mass. a. Haematoxylin and eosin staining revealed large tumor cells with polymorphic nuclei and organoids, trabecular growth, a coarse chromatin pattern, and prominent nucleoli. Immunohistochemical staining indicated that tumor cells were positive for CD56 (b), chromogranin A (c) and synaptophysin (d). The cellular proliferation marker Ki-67 was as high as 90% (e)