Fig. 2

Hematoxylin and eosin-stained paraffin section of the tumor at × 40 magnification shows that the tumor consists of small cells and large cells with hyperchromatic nuclei and a high mitotic rate, with nested, trabecular, and pseudoglandular growth patterns (a). Immunohistochemical analysis at × 40 magnification shows that these cells are positive for the neuroendocrine markers, synaptophysin (b) and CD56 (c). The Ki-67 index is greater than 20% (d)