Pancreatic tumors synaptophysin

The vesicle-associated membrane proteins (VAMP or synaptobrevin) occur in three isoforms and are proteins that are anchored to the cytoplasmic portion of synaptic membrane vesicles and secretory granules. VAMP2 and 3 are present in pancreatic beta cells, but the roles of this family of proteins have not been widely studied as markers of NE tumors. In contrast to synaptophysin and other synaptic vesicle proteins, SNAP-25 (synaptosomal protein of 25 KD) and syntaxin are present in the plasma membranes. At present, there are few studies on the application of these markers in diagnostic pathology... 

FIGURE 10.38 Distribution of markers in pancreatic endocrine tumors. SYN, synaptophysin NSE, neuron-specific enolase LMWCK, low-molecular-weight cytokeratin CgA, chromogranin A PC2, pro-convertase 2 PCM, peptidylglycine alpha-amidating enzyme PC3, proconvertase 3 NFP, neurofilament protein HCC(a), human chorionic gonadotropin alpha VIM, vimentin. 

DAs are typically negative for pancreatic enzymes such as trypsin, chymotrypsin, and lipase °76 unless there is a mixed acinar component, which is uncommon. They also fail to label with endocrine markers however, in 30% of DAs there are scattered, possibly non-neoplastic, endocrine cells in close association with the neoplastic cells, which can be highlighted with immunostains for chromogranin A, synaptophysin, and NSE.2 2 77-79 latter two markers can occasionally show more diffuse expression, which should not be regarded as evidence of neuroendocrine differentiation if the tumor is an otherwise conventional adenocarcinoma. 

Pancreatic endocrine neoplasm versus ACC Scattered endocrine cells or a focal endocrine component are common in ACC however, diffuse and strong reactivity for the endocrine markers (chromogranin and synaptophysin) throughout the tumor is characteristic of PENs. Additionally, PENS do not show immunoreactivity for acinar markers. 

Chejfec G, Falkmer S, Grimelius L, et al. Synaptophysin. A new marker for pancreatic neuroendocrine tumors. Am J Surg Pathol. 1987 11 241-247. 

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