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It has been clarified that myoepithelial cells contain S-100 protein which is known to be a marker protein of neural tissue. To evaluate the participation of myoepithelial cells in the histogenesis of the salivary gland tumors, normal salivary glands and various salivary gland tumors were stained by immuno-peroxidase method. PAP kits (DAKO Co, USA) for the S-100 protein and the Cytokeratin were used and the following resulting were obtained. Acinic cells of the normal salivery gland were negative for both cytokeratin and S-100 protein. The intercalated duct cells were weakly positive for cytokeratin and S-100 protein. The normal myoepithelial cells scattered around the acini and the intercalated ducts were positive only S-100 protein. In contrast, the striated duct were positive only for cytokeratin. In plemorphic adenoma, the S-100 protein positive cells were found in solid sheets of tumor cells, in chondromyxoid areas and in areas of spindle-cell stroma as well as in the outer layer of the tubular structures. Only the inner lining of the tubules were positive for cytokeratin. In basal cell adenoma, the stromal spindle cells were strongly positive for S-100 protein and the epithelial cells weakly positive. When tubules were present within the epithelial sheets, the inner most lining cells were positive for cytokeratin. The peripheral palisaded tumor cells were negative for both substances. By immunostaining of the adenoid cystic carcinoma, S-100 protein containing cells were found focally scattered independently on the variety of histologies. The lining cells of true cystic structure were positive for cytokeratin. Immunostaining of the mucoepidermoid carcinoma demostrated that the squamous cells and the tubular epithelial cells contained cytokeraitn, whereas only a few intermediate cells were positive for S-100 protein. In Warthin's tumor there were no S-100 protein positive cells, although basally located epithelial cells of the papillae were positive for cytokeratin. These findings suggest that salivary gland tumors other than the Warthin's tumor arise from myoepithelial cells or reserve cells having dual potentiality differentating into myoepithelial and intercalcated duct cells.

Pancreas is an endocrine organ as well as an exocrine one. The pancreatic neuroendocrine tumor (PNET) is an epithelial tumor with features of endocrine differentiation. Its incidence is progressively increasing now. Because the prognosis of PNET is much better than that of ductal adenocarcinoma, the precise diagnosis and proper treatment is more important than ever. Recently World Health Organization (WHO) and American Joint Committee on Cancer (AJCC) published the new WHO 2010 classification and the unified staging system of the PNET unlike the other gastrointestinal tract. Here, recent update of pathology of PNET will be discussed with their basic morphologic characteristics and essential points in the pathology report.
Adenocarcinoma ; Chromogranin A ; Gastrointestinal Tract ; Incidence ; Joints ; Neuroectodermal Tumors, Primitive ; Neuroendocrine Tumors ; Pancreas ; Prognosis ; World Health Organization