SYP is a calcium binding integral-membrane glycoprotein, 38 kDa of presynaptic vesicles in all neurons (Fig. 1A)and corresponding vesicles in all neuroendocrine (NE) cells (Fig. 1B). Moreover SYP is detected in choroid plexus epithelium. Staining is also seen in adrenal cortical cells, goblet cells and Paneth cells, probably due to a closely related protein.
SYP is detected in virtually all neuronal tumours: Neuroblastoma, ganglioneuroblastoma, ganglioneuroma, ganglioglioma, central neurocytoma, and phaeochromocytoma/paraganglioma. SYP may also be detected in other neural crest derived tumours like oligodendroglioma, astrocytoma (Fig. 2A) and ependymoma, however, to a varying extend. Moreover synaptophysin is detected in NE tumours like pancreatic islet tumours, carcinoid (Fig. 2B) and neuroendocrine carcinoma, small cell carcinoma, medullary thyroid carcinoma (Fig. 2C), and pituitary and parathyroid adenomas.
Also adrenal cortical tumours stain for synaptophysin (Fig. 2D).
SYP is a sensitive marker for the identification of neuronal and NE tumours and NE differentiation. However, it is not as specific as chromogranin A. SYP may also be used for the identification of adrenal cortical tumour.
The staining product should be granular cytoplasmic. mAbs clone 27G12 and clone Snp88 are useful Abs. Also several pAbs are available (we have obtained good results with pAb A0010 from Dako). A slight nuclear staining with clone snp88 may be seen, but without interference with the interpretation. mAb clone SY38, which is the oldest on the market, has been widely used. However, in our experience, the signal-to-noise ratio is poor with SY38 compared to newer Abs.
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