Recently, WHO adopted a new classification of endocrine tumors of the pancreas based on clinical and pathological criteria such as: tumor size, local invasion, necrosis, structural atypia with prevalence of broad solid areas, cellular atypia with high nuclear cytoplasmic ratio, irregular distribution of chromatin, number of mitoses/10HPF, Ki 67 positive tumor cells, perineural and angioinvasion, tumor cells with immunoreactivity to neuroendocrine markers (synaptophysin, chromogranin A, insulin, proinsulin detected by immunohistochemistry), nuclear p53 protein accumulation [6, 7]. Here, INS is linked to neoplasm.