Figure 1.

Histological examination of SNUC after H&E staining reveals characteristic hypercellular proliferation with a trabecular growth pattern, medium to large pleomorphic and hyperchromatic nuclei, inconspicuous to prominent nucleoli, varying amount of eosinophilic cytoplasm, high nuclear-to-cytoplasmic ratio. Immunohistochemistry is negative for synaptophysin, positive for pancytokeratin, negative for lymphoid markers (not shown), S100 (not shown), HMB45 (not shown). Electron microscopy demonstrates undifferentiated polygonal cells with sparse intracellular membrane structures; and numerous polyribosomes, mitochondria (figure 1, insert A.), and abundant lipid-filled vacuoles. Occasional tonofilaments and microtubules (figure 1, insert B.), are visible, along with membrane-bound, dense-core, neurosecretory granules (figure 1, insert C.),