Fig. 3

Neuroendocrine tumor with typical growth pattern. Tumor cells show intermediate cytological pleomorphy and a distinct ‘‘pepper and salt’’ chromatin of the nucleolus as well as details of the so called “Zellballen” or nesting pattern (a). Antibodies directed against chromogranin a show a strong staining pattern (b) while synaptophysin is intermediately expressed (c). Immunohiostochemical staining with antibodies against Ki-67 indicate a low proliferation rate <2 % (d)